2010 USRDS Annual Data Report
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Appendices

Sections this chapter: 

In this appendix we describe the datasets and methods used for the analyses in this volume. Appendix B includes information on USRDS products and services. Data management and preparation, database definitions, and the data sources used for ESRD analyses are described in the appendix of Volume Two.

Data sources

The USRDS maintains a stand-alone database with data on diagnoses and demographic characteristics of CKD and ESRD patients, along with biochemical data, dialysis claims, and information on treatment and payor histories, hospitalization events, deaths, physician/supplier services, and providers.

CMS MEDICARE ENROLLMENT DATABASE

The Enrollment Database (EDB) of the Centers for Medicare and Medicaid Services (CMS) is the designated repository of all Medicare beneficiary enrollment and entitlement data, and provides current and historical information on residence, Medicare as secondary payor (MSP) and employer group health plan (EGHP) status, and Health Insurance Claim/Beneficiary Identification Code (HIC/BIC) cross-referencing.

ESRD MEDICAL EVIDENCE FORM (CMS 2728)

The ESRD Medical Evidence (ME) form is the official form for registering ESRD patients, and must be submitted by dialysis or transplant providers within 45 days of ESRD initiation. The CMS, USRDS, and renal research communities rely on the ME form to ascertain basic patient demographic attributes, the primary cause of renal failure, major comorbidities, and biochemical test results at the time of ESRD initiation.

The third key revision of the ME form, released in May, 2005, was meant to remedy several shortcomings found in the 1995 form and its earlier version. Key additions target pre-ESRD care and vascular access use, and additional new fields collect information on glycosylated hemoglobin and lipid testing, on the frequency of hemodialysis sessions, and on whether patients are informed of transplant options.

ESRD DEATH NOTIFICATION FORM (CMS 2746)

The ESRD Death Notification form is used as the official form for reporting the death of individual patients with ESRD. According to CMS policy, this form must be submitted by dialysis or transplant providers within 30 days of a patient's death, and provides the date and causes of death (primary and secondary), reasons for discontinuation of renal replacement therapy, if applicable, and evidence of hospice care prior to death. It is the primary source of death information for CMS and the USRDS, identifying more than 99 percent of deaths. The USRDS also utilizes the Social Security Administration's (SSA) Death Master File as a supplemental data source for ascertaining death in a small group of lost-to-follow-up ESRD patients; this file, however, identifies only all-cause deaths.

CMS 5 percent STANDARD ANALYTICAL FILES (SAFs)

These files contain billing data from final action claims, submitted by Medicare beneficiaries, in which all adjustments have been resolved. The claims data are selected randomly from general Medicare claims (i.e. final action claims) using five combinations of the last two digits of the CMS Health Insurance Claims (HIC) number: 05, 20, 45, 70, and 95. Since the same two-digit numbers are used each year to create the 5 percent general Medicare SAFs, one should expect to see the same beneficiaries in these annual datasets. These claims are categorized into the inpatient (IP), outpatient (OP), home health agency (HHA), hospice (HS), skilled nursing facility (SNF), physician/supplier (PB), and durable medical equipment (DME) SAFs.

The files are updated each quarter through June of the next year, when the annual files are finalized. Datasets for the current year are created six months into the year and updated quarterly until finalized at 18 months, after which they are not updated to include late arriving claims. Annual files are thus approximately 98 percent complete. The USRDS 2010 ADR includes all claims up to December 31, 2008.

MEDICARE CURRENT BENEFICIARY SURVEY (MCBS)

The MCBS is a longitudinal survey of a nationally representative sample of aged, disabled, and institutionalized Medicare beneficiaries. It contains information on the health status, health care use and expenditures, drug prescriptions, health insurance coverage, and socioeconomic and demographic characteristics of the entire spectrum of Medicare beneficiaries. Data are made available by CMS in two datasets: Access to Care (1992–2007), and Cost and Use (1992–2006), with the 2007 and 2006 files, respectively, the latest updates for the 2010 ADR.

In the fall of 1991, the MCBS began to be conducted three times per calendar year (winter, summer, and fall), and in 1994 a sample rotation scheme was introduced. Survey participants are kept in the sample for four years, with approximately one-third rolling off, and new participants added each fall to keep the overall sample size at approximately 12,000 each calendar year.

CMS PRESCRIPTION DRUG EVENT (PDE) FILE

In December 2003, Congress passed the Medicare Prescription Drug, Improvement, and Modernization Act (MMA), amending the Social Security Act by adding Part D under Title XVIII. With this new Part D coverage, health plans must submit a summary record called the prescription drug event (PDE) record to CMS whenever a Medicare beneficiary fills a prescription. The PDE record contains 37 data elements; the USRDS receives PDE records with 30 elements, excluding a few non-critical fields. Each drug is identified by a National Drug Index (NDC) code; the record also contains prescription dosing information, drug costs above and below the out-of-pocket threshold, other true out-of-pocket (TrOOP) amounts, plan paid amounts, and low-income cost-sharing subsidy amounts.

Due to delays in the availability of the data, only the 2006 and 2007 PDE files were available for the 2010 ADR. The USRDS will, however, include both 2008 and 2009 PDE data in its 2011 ADR.

THOMSON reuters MARKETSCAN DATA

The Thomson Reuters MarketScan Commercial Claims and Encounters Database includes specific health services records for employees and their dependents in a selection of large employers, health plans, and government and public organizations. The database includes nine files: Annual Enrollment Summary Table, Enrollment Detail Table, Inpatient Admissions Table, Inpatient Services Table, Outpatient Services Table, Outpatient Pharmaceutical Claims Table, Facility (Inpatient and Outpatient) Header Table, Aggregated Populations Table, and the Red Book (prescription drug information by National Drug Code). The strength of this database lies in the quality of its cost information, where claims data include actual paid dollars and net payments by the insurer.

The MarketScan database links billing and encounter data to detailed patient demographic and enrollment information across sites and types of providers, and includes commercial health data from approximately 100 payors; about 80 percent of those covered are self-insured. Each year the database contains health data for about 10.5 million people. For details about the MarketScan data, please visit www.usrds.org.

INGENIX i3 DATA

The Ingenix i3 database is a commercial, non-capitated health plan database covering employees from multiple employers within a single insurer. In addition to the usual service encounter and drug data, it also includes laboratory data, allowing for comparisons between claims-based and lab-based definitions of diseases. To protect the discount structure of its business, the billing data of this single insurer discloses only charged dollars without actual paid amounts or the portion paid by the insurer.

The Ingenix i3 database links billing and encounter data to detailed demographic and enrollment information of individual employees from 2000 to 2008, and contains health data for about 14 million people annually. For details about what is contained in the Ingenix i3 data, please visit our website at www.usrds.org.

NATIONAL HEALTH & NUTRITION EXAMINATION SURVEY (NHANES)

NHANES is a series of health examination surveys conducted by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC). Begun in 1959, NHANES is designed to monitor the health and nutritional status of the non-institutionalized civilian population in the United States. NHANES III was conducted in two phases between 1988 and 1994. In 1999, NHANES became a continuous annual survey to allow annual estimates, with release of public-use data files every two years. Both NHANES III and NHANES 1999–2006 were nationally representative cross-sectional surveys and used a complex, stratified, multi-stage probability cluster sampling design that included selection of primary sampling units (counties), household segments within the counties, and sample persons from selected households. Survey participants were interviewed in their homes and/or received standardized medical examinations in mobile examination centers. Both surveys over-sampled African Americans, Mexican Americans, and individuals age 60 or older to improve the estimates for these subgroups.

PAYORS

Information on payors is obtained from the CMS EDB. We also examine Medicare outpatient claims to identify patients for whom the EDB does not indicate Medicare as primary payor (MPP), but who have at least three consecutive months of dialysis treatment covered by Medicare; these patients are also designated as having MPP coverage. From these two data sources we construct a payor sequence file to define payor history, and, starting with the 2003 ADR, we use this file to identify Medicare eligibility status and other payors.

The construction of this file is similar to that of the treatment history file. Payor status is maintained for each ESRD patient from the first ESRD service date until death or the end of the study period. Payor data are used to categorize a patient as MPP, Medicare as secondary payer (MSP) with EGHP, MSP non-EGHP, Medicare Advantage (Medicare + Choice), Medicaid, or a combination of payors. With this approach, the USRDS is now able to apply payor status information in all outcome analyses using the "as-treated" model (see the discussion of Chapter Eleven in Volume Two).

UNITED STATES CENSUS

In rate calculations throughout this year's ADR we use data from the 2000 U.S. Census, and incorporate CDC population estimates by race.

EGHP DATA

To examine the demographic segment represented by the EGHP data, we use enrollment information to construct yearly cohorts of enrollees younger than 65. To ensure that we select enrollees with the potential to generate claims evidence appropriate to the demands of analytical methods, rules for inclusion also include 12 months of continuous coverage in a commercial fee-for-service plan, and, for medication analyses, continuous prescription drug coverage. Comorbidities are identified using claims. Patients with at least one inpatient claim or at least two outpatient claims during the period of interest and with a diagnosis code of a particular comorbidity are identified as having that comorbidity.

ESRD COHORT IN THE EGHP POPULATION

Because the MarketScan and Ingenix i3 databases do not provide identifiable data elements, we are unable to link them directly to the USRDS ESRD registry. To identify ESRD patients, we therefore use a process similar to that used in the registry. Transplant patients are identified by evidence of a kidney transplant procedure or an adverse graft event, and chronic dialysis patients by evidence of continuous history of dialysis therapy, with at least three consecutive months of dialysis service and with dialysis service claims in at least 70 percent of treatment months. Treatment months are defined by the period from the first dialysis claim to the earliest of kidney transplant, death, or end of enrollment. Both inpatient and outpatient claims are evaluated for evidence of dialysis service history.

The first ESRD service date is set to the earliest of the first dialysis service date or the transplant date. If neither is available, the start of enrollment is used. Incidence is defined by a first ESRD service date at least 60 days after the start of enrollment.

IDENTIFICATION OF MAJOR COMORBIDITIES

According to a previously validated method for using Medicare claims to identify diabetic patients, a patient is diabetic if, within a one-year observation period, he or she has a qualifying ICD-9-CM diagnosis code of diabetes on one or more Part A institutional claims (inpatient, skilled nursing facility, or home health agency), or two or more institutional outpatient claims and/or physician/supplier claims. We employ the same methodology to identify major comorbidities, using the following codes: diabetes, 250.xx, 357.2, 362.0x, and 366.41; hypertension, 362.11, 401.x–405.x, 437.2; CKD, 016.0, 095.4, 189.0, 189.9, 223.0, 236.91, 250.4, 271.4, 274.1, 283.11, 403.x1, 403.x0 (after October 1, 2006), 404.x2, 404.x3, 404.xo and 404.x1 (after October 1, 2006), 440.1, 442.1, 447.3, 572.4, 580–588, 591, 642.1, 646.2, 753.12–753.17, 753.19, 753.2, and 794.4; congestive heart failure, 398.91, 402.x1, 404.x3, 422.xx, 425.xx 428.xx, V42.1; and CVD (other than CHF), 404.x1, 410–414, 420–421, 423–424, 426–427, 429, 430–438, 440–444, 447, 451–453, 557, 785.0–785.3, V42.2, V43.3, V45.0, V45.81, V45.82, and V53.3.

Prιcis

For a description of analytical methods related to age, gender, race, ethnicity, comorbidity, CKD stage, and estimated glomerular filtration rate in Table p.a, see the discussion for Chapter One, below.

Additional figures and tables in the Prιcis are taken directly from the chapters; methods for each can be found in the chapter discussions.

Chapter One chronic kidney disease in the general population  Top

Database design, setting, & study participants

The surveys used in this chapter include NHANES III (1988–1994), NHANES 1999–2000, NHANES 2001–2002, NHANES 2003–2004, and NHANES 2005–2006, and populations are limited to participants age 20 and older. The public use NHANES III Linked Mortality File provides mortality follow-up data from the date of NHANES III survey participation (1988–1994) through December 31, 2006. Study populations using these data are limited to participants age 20 and older, and the mortality follow-up month is greater than zero.

Measurements

In this chapter age is defined as the participant's age at the time of the household interview, and grouped into ages 20–39, 40–59, and 60 and older. Race/ethnicity is defined as non-Hispanic white, non-Hispanic African American, and other, and ethnicity as Hispanic (including Mexican-American and other Hispanic) and non-Hispanic only.

Obesity is defined as a BMI of 30 kg/m2 or above.

Participants with self-reported diabetes are those ever told by a doctor that they have diabetes or sugar diabetes (other than during pregnancy). In NHANES 1999–2006, participants answering "borderline" are classified as non-diabetic. Participants with self-reported congestive heart failure are those ever told by a doctor that they have congestive heart failure. And participants with self-reported cardiovascular disease are those with at least one of the following self-reported diseases: coronary heart disease, angina/angina pectoris, heart attack, congestive heart failure, or stroke.

Smokers are identified by an affirmative answer to the question: "Have you smoked at least 100 cigarettes during your entire life?" then further classified by their answer to the question: "Do you smoke cigarettes now?" Those with affirmative answers are classified as smokers; others are defined as non-smokers.

WHO anemia is defined as a hemoglobin less than 13 g/dl in males and less than 12 g/dl in females.

Self-reported hypertension is identified by an affirmative answer to the question: "Have you ever been told by a doctor that you had hypertension, also called high blood pressure?"

In NHANES 1999–2006, systolic blood pressure (SBP) / diastolic blood pressure (DBP) for each participant is calculated as the mean of all measured SBP / DBP.

Microalbuminuria is defined by the ratio of urinary albumin (mg/l) to urinary creatinine (mg/dl; ACR). Participants with a valid ACR are classified as having microalbuminuria if this value is not less than 30 mg/g.

The glomerular filtration rate (ml/min/1.73 m2) is estimated by three methods. The first is the MDRD method, using the standardized creatinine value for NHANES III and NHANES 1999–2000, 2001–2002, 2003–2004, and 2005–2006, separately, based on NCHS recommendations. The equation used to estimate the GFR is as follows (Levey et al.): estimated GFR = 175 * (standardized serum creatinine in mg/dl)**(-1.154) * age**(-0.203) * (0.742 if female) * (1.212 if African American).

Second is the CKD-EPI method, based on the standardized creatinine value for the NHANES cohorts, as listed above. The equation is as follows (Levey et al.): estimated GFR = 141 * min(Scr /?, 1)**a * max(Scr/?, 1)**(-1.209) * 0.993**age * 1.018 [if female] * 1.159 [if African American], where Scr is standardized serum creatinine in mg/dl, ? is 0.7 for females and 0.9 for males, a is -0.329 for females and -0.411 for males, min indicates the minimum of Scr/ ? or 1, and max indicates the maximum of Scr/? or 1.

The third method is based on cystatin C only (Stevens et al.), which is available only for NHANES III, NHANES 1999–2000, and NHANES 2001–2002: estimated GFR = 76.7 * cystatin C **(-1.19).

CKD is defined as an eGFR less than 60 ml/min/1.73 m2, or an eGFR of 60 or greater in the presence of microalbuminuria. CKD stages are defined as follows: Stage 5, eGFR < 15; Stage 4, 15 = eGFR < 30; Stage 3, 30 = eGFR < 60; Stage 2, ACR = 30 and 60 = eGFR = 89; and Stage 1, ACR = 30 and eGFR = 90. These are the standard CKD definitions used in this chapter.

Statistical analysis

To obtain national estimates of each statistic, the odds ratios, sampling weights, and survey design are implemented by SUDAAN (Research Triangle Institute, Research Triangle Park, NC). Standard errors are estimated using the Taylor Series Linearization method for NHANES III and NHANES 1999–2006. GFR is estimated by the method indicated in the figure titles. CKD includes Stages 1–5; all other comorbidities are self-reported.

Table 1.e and Figure 1.10 present data on awareness, treatment, and control of various metabolic markers by CKD stage. Patients are classified as hypertensive if measured systolic blood pressure is = 140 mmHg (= 130 mmHg for CKD or diabetic patients) or measured diastolic blood pressure is = 90 mmHg (= 80 mmHg for CKD or diabetic patients), or if they self-report currently taking a prescription to control hypertension. Patients are classified as being aware of hypertension if they report having been told they have high blood pressure, are classified as being treated for hypertension if they report currently taking a prescription to control hypertension, and are considered in control of hypertension if current blood pressure is < 140/< 90 (< 130/< 80 for CKD or diabetic patients).

Control of hyperlipidemia is assessed in a similar fashion. Hyperlipidemia is defined as a measured LDL cholesterol above the ATP III target range (= 160 mg/dl for patients with 0–1 risk factors, = 130 mg/dl for patients with two or more risk factors, = 100 mg/dl for patients with coronary heart disease (CHD) and CHD risk equivalents). CKD is classified as a CHD risk equivalent. Awareness of hyperlipidemia is assessed by self-report of being told by a doctor that blood cholesterol level is high, and patients are classified as being treated for hyperlipidemia if they report currently taking a cholesterol medication or dieting to control cholesterol. Control is defined as meeting the ATP III LDL target for the appropriate risk category, as described above. Current control of HDL cholesterol and total cholesterol are also presented in Table 1.e and Figure 1.11–12; awareness and treatment, however, are not assessed, since LDL cholesterol is currently the recommended target of therapy.

Control of diabetes is presented in Table 1.e and Figure 1.13. Diabetic patients are identified by self-report, as described above. Control of diabetes is assessed as a glycosylated hemoglobin (A1c) of less than 7 percent, as recommended by the American Diabetes Association.

Chapter Two Chronic kidney disease identified in the claims data  Top

Figure 2.1 illustrates the extent of point prevalent diabetes, cancer, congestive heart failure, and CKD in the general Medicare population. Methods are the same as those described at the beginning of Chapter Nine.

Table 2.a compares the characteristics of prevalent general Medicare, MarketScan, and Ingenix i3 CKD patients by age, gender, comorbidity, and occupation in 2008. Each comorbidity is defined by medical claims (one inpatient or two outpatient) during each calendar year. Figures 2.2–3 include prevalent Medicare (age 65 and older) and MarketScan and Ingenix i3 (age 20–64) patients, without ESRD, and surviving 2008; Figure 2.2 also excludes patients with CKD in 2007. CKD is also defined by medical claims (one inpatient or two outpatient) during each calendar year.

Figures 2.4–6 and 2.10–13 illustrate the incidence, and Figures 2.7–9 and 2.14–17 the prevalence, of recognized CKD in the Medicare, Marketscan, and Ingenix i3 datasets. The 5 percent Medicare sample includes patients age 65 and older, without ESRD, surviving throughout the cohort year with Medicare as primary payor, and not enrolled in Medicare Advantage. The MarketScan and Ingenix i3 cohorts are constructed in a similar fashion, but restricted to patients age 20–64, enrolled in a fee-for-service plan, and without ESRD. Patients with CKD in the prior year are excluded when defining incident CKD.

Table 2.b and Figures 2.18–19 illustrate the percentage of prevalent CKD patients with different comorbidities, and include general Medicare patients age 65 and older with both inpatient/outpatient and physician/supplier coverage during the calendar year. All patients survive to the end of each calendar year; ESRD patients are excluded. All comorbidities are identified by claims (one inpatient or two outpatient) during each calendar year.

In Table 2.c and Figure 2.21–26, CKD is defined as follows: Stage 5: eGFR < 15 ml/min/1.73 m2; Stage 4: 15 = eGFR < 30; Stage 3: 30 = eGFR < 60; stage 3-5: eGFR < 60. Comorbidities such as hypertension, CVD, COPD, hepatitis C, cancer, anemia, and liver disease, along with hospitalization, are defined from claims; other metabolic abnormalities are defined from laboratory test results. GFR is estimated using both the MDRD and the CKD-EPI equations.

Figure 2.20 illustrates the distribution of eGFR by CKD diagnosis codes, and includes CKD defined using all codes, CKD stage diagnosis codes (585.x), diabetes with renal manifestations (250.4), and hypertensive kidney disease with CKD (403.x1). GFR is estimated using both the MDRD and the CKD-EPI equations.

Chapter Three Care of patients with chronic kidney disease  Top

Figure 3.1 shows the cumulative probability of non-CKD patients receiving a first urinary microalbumin measurement at month 12 in the second year of each two-year period. The general Medicare population includes patients continuously enrolled in the Medicare inpatient/outpatient and physician/supplier program during the first year, and age 65 or older at the beginning of that year. Patients are excluded if they are enrolled in a managed care program (HMO), acquire Medicare as secondary payor, die, are diagnosed with CKD or ESRD during the first year, have a missing date of birth, or do not live in the 50 states, the District of Columbia, Puerto Rico, or the Territories. The Ingenix i3 population includes patients continuously enrolled in a fee-for-service plan in the first year and age 50–64 during that year; patients diagnosed with CKD or ESRD during that year are excluded.

For both populations, patients are followed from January 1 to December 31 of the second year for the first urinary microalbumin measurement. The Kaplan-Meier method is used to calculate the cumulative probability. Medicare patients are censored at death, development of ESRD, and change in payor status, while Ingenix i3 patients are censored at plan change date and development of ESRD.

CPT codes used to define urinary microalbumin measurement are 82042, 82043, 82044, and 84156. Diabetes and hypertension are defined in the first year. Methods of defining CKD, diabetes, and hypertension are the same as those described above in the section titled "identification of major comorbidities."

Figure 3.2 includes patients from the 5 percent Medicare sample, age 66 and older, who survive all of 2008 with Medicare as primary payor and are not enrolled in Medicare Advantage; patients with CKD or ESRD in 2007 are excluded. The first CKD claim is identified in 2008 by the regular CKD diagnosis codes, excluding 584. Calendar year 2007 is used to define diabetes and congestive heart failure by the standard method, and the Kaplan-Meier method is used to obtain the cumulative probability. The same method is used for 2002 and 2005. The MarketScan and Ingenix i3 cohorts are constructed in a similar fashion, but restricted to patients age 50–64 who are enrolled in a fee-for-service plan.

A similar cohort is used in Figure 3.3, but only ESRD patients are excluded. The first nephrologist claim in 2002, 2005, and 2008 is identified for Medicare patients from the physician specialty codes on physician/supplier claims, for MarketScan patients from provider codes on inpatient and outpatient claims, and for Ingenix i3 patients from provider category codes on inpatient, outpatient, or physician/supplier claims. Figure 3.4 is similar, but restricted to patients with CKD.

Figure 3.5 includes patients from the 5 percent Medicare sample, age 66 and older, who survive all of 2007 with Medicare as primary payor and are not enrolled in Medicare Advantage, and who develop CKD in 2007; patients with CKD in 2006 or ESRD in 2007 are excluded. Calendar year 2007 is used to define CKD by the standard method, while calendar year 2006 is used to define diabetes and congestive heart failure, also by the standard method. The Kaplan-Meier method is then used to obtain the cumulative probability of a physician visit within one year of CKD diagnosis. MarketScan and Ingenix i3 cohorts are constructed in a similar fashion, but restricted to patients age 50–64 who are enrolled in a fee-for-service plan. The first nephrologist claim, primary care claim, or cardiology claim is identified as described for Figure 3.3. Constructed in a similar fashion, Figure 3.6 is restricted to 2007 CKD patients with diabetes, Figure 3.7 to 2007 CKD patients with congestive heart failure, and Figure 3.8 to 2007 CKD patients with both diabetes and CHF.

Figures 3.9–16 include 2007 CKD patients; and show the cumulative probability of testing during one year. The cohort for Figures 3.9–12 and 3.14–16 is the same as that described for Figure 3.4; the cohort in Figure 3.13 is similar, but limited to diabetic CKD patients. Patients are followed from January 1, 2008, to December 31, 2008, and the Kaplan-Meier method is used to obtain the cumulative probability. Tests are identified from HCPCS codes in outpatient and physician/supplier claims during the year, as follows: microalbumin testing, 82042, 82043, 82044, and 84156; creatinine testing, 80048, 80050, 80053, 80069, and 82565; calcium/phosphorus testing, 82310, 80048, 80050, 80053, 80069, and 84100; parathyroid hormone testing, 83970; lipid testing, 80061, 82465, 83700, 83701, 83715, 83716, 83717, 83718, 83719, 83720, 83721, and 84478; glycosylated hemoglobin testing, 83036 and 83037; hemoglobin testing, 85013, 85014, 85018, 85025, 85027, 80050, and 80055; and iron saturation testing, 83550, 83540, and 84466.

Figures 3.17–24 include CKD patients in the 2007 entry period, and show the cumulative probability of medication use during the 12-month study period in 2008. The study cohort includes MarketScan and Ingenix i3 patients age 20–64; MarketScan patients have fee-for-service coverage during the entry period and medical coverage and drug insurance during the study period, while Ingenix i3 patients have coverage with business type classified as commercial during both the entry and study periods. All comorbidities are defined by medical claims (one inpatient or two outpatient) during the entry period.

Figures 3.25–26 include 2008 CKD Ingenix i3 patients, age 50–64. Patients survive all of 2008, are enrolled in a fee-for-service plan for the entire year, and use a statin at least once during the year. Calendar year 2008 is used to define CKD, diabetes, and CHF by the standard method. For CKD patients on a statin, controlled total cholesterol is less than 200 mg/dl and controlled LDL is less than 100 mg/dl. Figures 3.27–28 use a similar cohort, but include only 2008 CKD patients with diabetes and with at least one use of diabetic drugs in 2008. The controlled A1c level is less than 7 percent.

Chapter Four Morbidity & mortality  Top

Hospitalization

Adjusted admission rates in this chapter include adjustment for baseline comorbidities and prior hospitalization in addition to patient demographics. A model-based adjustment method is used with a Poisson assumption, and includes data from the current and previous two years, with respective weights of 1, Ό, and ?. However, since stage-specific ICD-9-CM codes for CKD do not appear until 2006, models for adjusted rates by CKD stage (Table 4.a and Figures 4.2–6) include only two years of data: 2007 and 2008 point prevalent patients with CKD defined in 2006 and 2007, respectively, with weights of 1 and Ό. Adjusted rates reflect the distribution of a reference cohort specified below in the discussion of the respective figures. With this method, the parameter estimates from the model are used to calculate an estimated admission rate for each patient in the reference cohort. Adjusted rates are then computed as the weighted average of these individual rates, using as the weight the time at risk of each patient in the reference cohort.

Figure 4.1 compares all-cause hospital admission rates for CKD and non-CKD patients in prevalent Medicare and MarketScan cohorts. The study design consists of a one-year period during which CKD, comorbidities, and prior hospitalization are defined from claims, followed by the cohort year when follow-up for admissions begins on January 1. The Medicare cohort includes patients who are age 66 and older on December 31 of the prior year, residents of the 50 states, the District of Columbia, Puerto Rico, or the Territories, continuously enrolled in Medicare inpatient/outpatient and physician/supplier coverage, without HMO coverage, and without ESRD, and who survive the complete year prior to follow-up. The MarketScan cohort includes patients age 50–64 on December 31 of the prior year who remain without ESRD and enrolled in a fee-for-service commercial health plan during the prior year. Patients are followed for admissions from January 1 of the follow-up year, and are censored at ESRD initiation, end of plan coverage, or December 31; Medicare patients are also censored at death. Rates are adjusted for gender, prior hospitalization, diabetes, COPD, hypertension, liver disease, gastrointestinal disease, cancer, anemia, peripheral vascular disease, CVA/TIA, atherosclerotic heart disease, congestive heart failure, dysrhythmia, and other cardiac disease. The reference cohort includes Medicare patients in 2005, age 66 and older.

Table 4.a and Figure 4.2 show adjusted admission rates in Medicare patients age 66 and older. Study design, censoring, and inclusion criteria generally follow those described for the Medicare cohort in Figure 4.1. Groups for diabetes and congestive heart failure are mutually exclusive. Follow-up for hospital admissions starts on January 1, 2008, with the model-based adjustment method described above. Adjustment factors include those listed for Figure 4.1 in addition to age and race, and with diabetes and congestive heart failure combinations rather than as separate factors. Rates presented by one factor are adjusted for the others. The reference cohort includes Medicare patients in 2008, age 66 and older.

Figures 4.3–6 show adjusted all-cause and cause-specific admission rates by CKD diagnosis code and dataset. Again, study design, censoring, and inclusion criteria generally follow the description for the Medicare and MarketScan cohorts in Figure 4.1. Additionally, Ingenix i3 data include point prevalent patients on January 1, 2008, continuously enrolled in a fee-for-service or commercial health plan and without ESRD during 2007, and age 50–64 on December 31, 2007. The group labeled "CKD" includes those with claims-based evidence of CKD in 2007, while "non-CKD" is defined as patients without claims-based evidence of CKD. Rates are adjusted for the same factors listed for Figure 4.1. Cause-specific rates reflect hospital admissions for the purpose of the stated condition, and are identified by principal ICD-9-CM diagnosis codes for cardiovascular and infectious admissions listed in the description of Figure 6.2 in Volume Two. The reference cohort includes Medicare patients in 2008, age 66 and older.

Figures 4.7–12 illustrate geographic variations in admissions for pneumonia, bacteremia/septicemia, and urinary tract infection among Medicare patients point prevalent on January 1, 2008. Patients are 66 or older on December 31, 2007, and, during 2007, classified by their claims-based CKD status, without ESRD, and continuously enrolled in Medicare parts A and B, with no HMO coverage. Residents of Puerto Rico and the Territories are excluded. Follow-up begins on January 1, 2008, and unadjusted admission rates are presented by state. Cause-specific admissions are based on principal ICD-9-CM codes as follows: pneumonia, 480–486 and 487.0; bacteremia/septicemia, 038.0–038.9 and 790.7; and urinary tract infection, 590–590.9, 595–595.4, 597–597.89, 598, 599.0, 601–601.9, 604–604.9, 607.1–2, 608.0, 608.4, 616.1, 616.3–4, and 616.8.

Figures 4.13–15 present cause-specific hospital admission rates for Medicare patients age 66 and older. Study design, censoring, and inclusion criteria again follow the description for Figure 4.1. Admissions for pneumonia, bacteremia/septicemia, and urinary tract infection are identified by the principal ICD-9-CM diagnosis codes listed for Figures 4.7–12. Rates are presented by race and adjusted for age, gender, prior hospitalization, peripheral vascular disease, CVA/TIA, atherosclerotic heart disease, congestive heart failure, dysrhythmia, other cardiac disease, diabetes, COPD, hypertension, liver disease, gastrointestinal disease, cancer, and anemia. The reference cohort includes Medicare patients in 2005, age 66 and older.

Mortality

Figures 4.16–18 illustrate trends, by CKD status, in unadjusted and adjusted all-cause mortality by age, gender, and race. The study cohort for 1995 includes point prevalent Medicare patients on January 1, 1995, age 66 or older. CKD status is identified from 1994 Medicare claims, and the cohort excludes patients enrolled in an HMO, with Medicare as secondary payor, or diagnosed with ESRD in 1994. Follow-up extends from January 1, 1995, to December 31, 1995, and is censored at ESRD and the end of Medicare entitlement. Patients not living in the 50 states or the District of Columbia are excluded. Cohorts for 1996–2008 are constructed in a similar manner. Adjusted mortality is based on a Cox regression model and adjusted for demographics, hospitalization in the prior year, and comorbidities and sources of comorbidities defined in the prior year. Medicare patients from 2005 are used as the reference cohort.

Table 4.b shows adjusted rates of mortality per 1,000 patient years at risk in 2008 for patients with and without CKD, and by CKD stage. The cohort definitions are same as those defined in Figures 4.16–18. Adjusted mortality is based on a Cox regression model; rates by age are adjusted for gender, race, and comorbidities; rates by gender are adjusted for age, race, and comorbidities; and rates by race are adjusted for age, gender, and comorbidities. All 2008 patients are used as reference. Figure 4.19 is based on the results obtained from Table 4.b; adjusted mortality is adjusted for all of the above covariates.

Chapter Five Cardiovascular disease in patients with chronic kidney disease  Top

Figure 5.1 illustrates cardiovascular prescription drug use in 2007 Medicare enrollees with chronic kidney disease. Patients are alive and at least 66 years of age on January 1, 2007, survive and carry Medicare Parts A, B, and D during all of 2007, and are not enrolled in an HMO during 2007. Chronic kidney disease is defined from Medicare claims during 2006, and drug use by at least one prescription fill during 2007. Particular agents are identified from National Drug Codes on Part D claims, linked to the 2007 edition of Red Book.

Table 5.a describes prescription drug therapy in Medicare enrollees with their first diagnosis for cardiovascular disease (CVD) or receiving their first treatment for CVD in 2007. The index events for CVD include acute myocardial infarction (AMI), atrial fibrillation (AF), cerebrovascular accident/transient ischemic attack (CVA/TIA), congestive heart failure (CHF), and peripheral arterial disease (PAD), while the index events for CVD treatment include percutaneous coronary interventions (PCI), coronary artery bypass graft surgery (CABG), and use of implantable cardioverter defibrillators and cardiac resynchronization therapy with defibrillator (ICD/CRT-D).

For each of the index events, a study cohort is identified from the 2007 general Medicare database. Patients have the index event during 2007, are continuously enrolled in Medicare inpatient/outpatient and physician/supplier coverage, are not enrolled in an HMO during the one-year period before the index event, are 66 or older on the date of the index event, and reside in the 50 states, the District of Columbia, Puerto Rico, or the Territories. Patients diagnosed with ESRD prior to the index event are excluded. The twelve-month period prior to the index event is the baseline period, and CKD patients and CKD stage are identified based on Medicare claims during this period, using the same methodology described for Chapter Two. Patients with a pre-existing condition of the index event are also identified during the baseline period, but are not excluded in the analysis for Table 5.a.

Using the method employed to identify patients with CKD, we identify those with pre-existing AMI, AF, CVA/TIA, or CHF during the baseline period. ICD/CRT-D is defined through ICD-9-CM procedure codes in inpatient/outpatient claims, and PCI and CABG are identified through ICD-9-CM procedure codes in inpatient/outpatient claims or CPT codes in physician/supplier claims. PAD is defined through either diagnosis codes or procedure codes; if defined through diagnosis codes, we use the standard method; if defined through procedure codes, we employ the method used for PCI and CABG. AMI, AF, CVA/TIA, CHF, PAD, first PCI and CABG surgery, and the first use of ICD/CRT-D are defined on the date of the first appearance of diagnosis or procedure codes in the 2007 claims.

With the exception of AMI, the data sources and methods used to define each event are the same as those used in defining the pre-existing condition at baseline. The AMI event is defined as the first appearance of the diagnosis code on an inpatient claim.

The same codes are used to define AF, PAD, PCI, CABG, and ICD/CRT-D as pre-existing conditions at baseline and as an event in 2007, while different codes are used for CHF, CVA/TIA and AMI:
AF: 427.3 (ICD-9-CM diagnosis codes)
AMI, 410 and 412 for condition at baseline; 410, 410.x0, and 410.x1 for event (ICD-9-CM diagnosis codes)
CHF: 398.91, 422.xx, 425.x, 428.xx, 402.x1, 404.x1, 404.x3, and V42.1 for condition at baseline (ICD-9-CM diagnosis codes); 398.91, 425.x, 428.xx, 402.x1, 404.x1, and 404.x3 for event (ICD-9-CM diagnosis codes)
CVA/TIA: 430–438 for condition at baseline; 430–437 for event (ICD-9-CM diagnosis codes)
PAD: 440–444, 447, and 557 (ICD-9-CM diagnosis codes); 84.0, 84.1, 84.91, 39.25, 39.26, and 39.29 (ICD-9-CM procedure codes); 24900, 24920, 25900, 25905, 25920, 25927, 27295, 27590, 27591, 27592, 27598, 27880, 27881, 27882, 27888, 27889, 28800, 28805, 34900, 35131, 35132, 35141, 35142, 35151, 35152, 34051, 34151, 34201, 34203, 34800–34834, 35081–35103, 35331, 35341, 35351, 35355, 35361, 35363, 35371, 35372, 35381, 35450, 35452, 35454, 35456, 35459, 35470, 35471, 35472, 35473, 35474, 35480, 35481, 35482,35483, 35485, 35490, 35491, 35492, 35493, 35495, 35521, 35531, 35533, 35541, 35546, 35548, 35549, 35551, 35556, 35558, 35563, 35565, 35566, 35571, 35583, 35585, 35587, 35621, 35623, 35646, 35647, 35651, 35654, 35656, 35661, 35663, 35665, 35666, and 35671 (CPT codes)
CABG surgery: 36.1x (ICD-9-CM procedure codes); 33510–33523 and 33533–33536 (CPT codes)
PCI: 00.66, 36.01, 36.02, 36.05, and 36.06 (ICD-9-CM procedure codes); 92980–92982, 92984, and 92995–92996 (CPT codes)
ICD: 37.94 (ICD-9-CM procedure code)
CRT-D: 00.51 (ICD-9-CM procedure code)
Table 5.a and Figures 5.2–5 include Medicare enrollees with a CVD event between January 1, 2007, and November 30, 2007, discharged within two weeks of the date of the index event (if the enrollee was hospitalized at the time of the event), remaining outside the hospital at one month after the date of the index event, and carrying continuous Medicare Part D coverage during the interval from one month before to one month after the date of the index event; use of a particular drug is defined by at least one filling of a prescription for the drug during this interval. Drugs are identified from National Drug Codes included on Part D claims, and linked with the 2007 edition of Red Book.

Figure 5.6 describes all-cause survival in Medicare patients with a first diagnosis of CHF, AMI, AF, or CVA/TIA (index event) in 2007–2008. The study cohorts are constructed as for Table 5.a., except that the period searched for the index event extends to 2008. To estimate all-cause survival after CHF, patients with pre-existing CHF are excluded. Follow-up begins on the CHF diagnosis date and ends at the earliest of death, ESRD diagnosis, one year after CHF diagnosis, or December 31, 2008. The Kaplan-Meier method is used to estimate all-cause survival.

Figure 5.7 presents rates of rehospitalization for any disease and for rehospitalization/death in CKD patients with a first hospitalization or treatment for CVD (as described for Table 5.a) during 2007–2008. The cohorts are constructed as for Table 5.a, except that we first search Medicare Part A inpatient claims in 2007–2008 to identify Medicare enrollees who are admitted to the hospital for CVD or receiving CVD treatment (index hospitalization event) for the first time, and who are discharged alive. Patients diagnosed with ESRD prior to or on the discharge date are excluded. CKD patients are identified during the one-year period prior to the discharge date using the methodology described for Chapter Two. Patients with a pre-existing condition of the same index disease or treatment are identified during the one-year period prior to the admission date using the method described for Table 5.a.

To examine rates in patients admitted to the hospital for CHF, patients with pre-existing CHF are excluded. To track the occurrence of rehospitalization, follow-up begins on the day after the discharge date and ends at the earliest of rehospitalization for any disease, death, ESRD diagnosis, change of Medicare inpatient/outpatient and physician/supplier coverage, enrollment in an HMO, one year after discharge, or December 31, 2008. To track the occurrence of death, follow-up does not end at the admission date of rehospitalization; the combined event of rehospitalization and death is defined as the occurrence of either rehospitalization or death, and time to the combined event is time to rehospitalization or time to death, whichever is shorter. The event rate is calculated by dividing the total number of events by the total person-time at risk. The same method is then used to calculate rates after each of the other index hospitalization events.

Figure 5.8 presents, by CKD status and stage, the cumulative probability of rehospitalization for any disease and for the combined event of rehospitalization/death in Medicare patients with a first hospitalization for CHF, AMI, AF, or CVA/TIA during 2007–2008. Study cohorts are constructed as for Figure 5.7, including Medicare patients without CKD during one year prior to the index event. The follow-up time and the occurrence of outcomes are defined using the method employed in Figure 5.7, and the Kaplan-Meier method is used to estimate probabilities.

Figures 5.9–12 show geographic variations in rates of prevalent CHF, cardiac arrest, AMI, and CVA/TIA in 2008 for Medicare CKD and non-CKD patients. The study cohort includes point prevalent Medicare enrollees on December 31, 2007, age 66 and older, residing in the 50 states, the District of Columbia, Puerto Rico, or the Territories, continuously enrolled in Medicare inpatient/outpatient and physician/supplier coverage, and not enrolled in an HMO in 2007. Patients diagnosed with ESRD are excluded; those with CKD are identified using the method described for Chapter Two. To track the occurrence of CHF, AMI, CVA/TIA, and cardiac arrest, patients are followed from January 1, 2008, to the earliest of death, ESRD diagnosis, change of Medicare inpatient/outpatient and physician/supplier coverage, enrollment in an HMO, or December 31, 2008. Patients with CHF, AMI, and CVA/TIA are identified using the methods described for Table 5.a. Patients with cardiac arrest are identified through an ICD-9-CM diagnosis code of cardiac arrest (427.4 and 427.5) on a claim from either inpatient/outpatient institutional claims or physician/supplier claims. The proportion of patients with each of the four events in 2008 is calculated for each HSA or state by CKD status, and presented per 1,000 patients. HSA-level map data are smoothed using a Bayesian spatial hierarchical model (described in the section on statistical methods in the Volume Two appendix).

Figures 5.13–16 illustrate geographic variations in prescription drug use in Medicare CKD and non-CKD patients with a first diagnosis for CHF or AF in 2007. Methods for cohort construction and identification of prescription drug use are those used in Table 5.a. CHF medications include angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and beta blockers, while atrial fibrillation medications include warfarin, clopidogrel, and amiodarone.

Figures 5.17–19 illustrate the distribution of prescription drug use in Medicare CKD and non-CKD patients with a first diagnosis for CHF, AMI, or AF in 2007. Methods for cohort construction and identification of prescription drug use are as those used in Table 5.a.

Total solar eclipse photographed by Charles A. Herzog, MD, on March 7, 1970, Virginia Beach, Va. Nikkormat FTn with 90–230mm Soligor zoom lens and 2X "Tel-extender" for effective focal length of 460mm. Exposure: ½ second at F9; film: high speed Ektachrome (400 ASA).

Chapter Six Outcomes in the transition zone in nursing home patients with ckd  Top

ESRD patients

The ESRD cohort in this chapter includes nursing home patients initiating ESRD in 2004–2006, age 65 and older at the time of ESRD, and in the nursing home at least 90 days, with at least one Minimum Data Set (MDS) assessment prior to ESRD. Included patients either die or remain in the nursing home for one year after ESRD. Baseline and follow-up are as follows:

Baseline: up to 180 days prior to ESRD. Assessment used is the last one prior to ESRD.
follow-up period one: Assessment used is the first one at least 10 days after ESRD, but allowed to be as late as 60 days after ESRD.
follow-up period two: Assessment used is the closest one to 180 days (six months) after ESRD, but allowed to be as early as 150 days (five months) after ESRD. If there is no valid assessment during that period, the first assessment between 180 and 210 days after ESRD is used.
follow-up period three: Assessment used is the closest one to 360 days (12 months) after ESRD, but allowed to be as early as 330 days (11 months) after ESRD. If there is no valid assessment during that period, the first assessment between 360 and 390 days after ESRD is used. CKD & non-CKD patients

The CKD and non-CKD cohorts in this chapter include Medicare patients from the 5 percent sample, 2004–2005, in the nursing home and age 65 and older as of December 31 of those years. CKD is identified from claims (one inpatient or two or more outpatient/Part B claims) during 2004 or 2005. Included patients either die or remain in the nursing home for the entire calendar year; those who progress to ESRD are excluded. MDS data during 2004–2006 are then used, and baseline and follow-up are as follows:

Baseline: up to 180 days prior to January 1 of the year. Assessment used is the last one prior to January 1 of the year.
follow-up periods one to three: the same methodology is used as for the ESRD patients, substituting January 1 of the appropriate year for the ESRD date.
Demographic information in Figure 6.1 is obtained from either the USRDS demographic profile (ESRD patients), or the 5 percent denominator file (CKD and non-CKD patients). Comorbidity is obtained from MDS assessments from up to one year prior to baseline.

There are several types of scores calculated from the MDS assessments at each time period: memory scores in Figures 6.2–4, decision scores in Figures 6.5–7, scores related to making oneself understood in Figures 6.8–10, and Activities of Daily Living (ADL) scores in Figures 6.11–14 and Table 6.a. These are calculated as follows:
memory score (0–6 points): B2a = 0 (1 point), B2b = 0 (1 point), B3a–d (1 point for each checked answer)
decision score (0–3 points): B4 = 0 (3 points), 1 (2 points), 2 (1 point), 3 (0 points)
understood score (0–3 points): C4 = 0 (3 points), 1 (2 points), 2 (1 point), 3 (0 points)
ADL score (0–28 points): 0–4 points from each of the following questions, based on what was reported. 0 = independent (0 points), 1 = supervision (1 point), 2 = limited assistance (2 points), 3 = extensive assistance (3 points), 4 = total dependence (4 points).
G1a: bed mobility
G1b: transfer
G1c: walk in room (a value of 8 = 'did not occur in last 7 days' was given 4 points)
G1g: dressing
G1h: eating
G1i: toilet use
G1j: personal hygiene
Most figures are self-explanatory. For Figures 6.4, 6.7, 6.10, 6.13, and 6.14, patients are required to survive with an assessment for the two periods being compared. That is, some of the patients included in the calculation of "average change" from "baseline to follow-up one" may die in follow-up periods two or three.

The distribution of ADL scores in Figure 6.11 for each time period excludes patients who die during or prior to that particular period.

Unadjusted survival in Figure 6.15 is from Kaplan-Meier methods. The overall adjusted relative risk of death in Figure 6.16 is adjusted for age, race, and gender; the RR for one category is adjusted for the remaining ones. In Figures 6.15–16 and Table 6.b, patients are considered to have died during a follow-up period if they die before the end of the period (60, 210, or 390 days) and have no valid assessment in that period prior to death.

Chapter Seven The transition to end-stage renal disease  Top

Figures 7.1–6 include incident ESRD patients (Medicare patients are limited to those age 67 and older). For Figure 7.2, the type of CKD claim represents the code present on the first CKD claim. If there are multiple CKD claims and/or codes on the same date as the first claim, the type of claim is determined by the following hierarchy: 585.4, 585.3-5, 585.1-2, 585.9/other. In Figures 7.3–6, CKD stage, identified from claims, is defined using the highest coded stage in quarters -8 to -5. Physician specialty is identified from claims; physician visits in Figure 7.3 include those to a primary care physician, cardiologist, or nephrologist, while in Figure 7.6 primary care represents family practice, general practice, and internal medicine. Inpatient and outpatient locations are identified by location code or the source of the claim, depending on the dataset.

Figures 7.7–12 include incident ESRD patients in 2008, and show the cumulative percentage of patients with at least one test during the four quarters before the first ESRD service date. Tests are identified from outpatient and physician/supplier claims during the two years, as follows: microalbumin, HCPCS codes 82042, 82043, 82044, and 84156; parathyroid hormone, HCPCS code 83970; creatinine, HCPCS codes 80048, 80050, 80053, 80069, and 82565; lipid, HCPCS codes 80061, 82465, 83715, 83716, 83717, 83718, 83719, 83720, 83721, and 84478; and glycosylated hemoglobin, HCPCS codes 83036 and 83037. For glycosylated hemoglobin testing, patients must be defined with diabetes during the 24 months before incident ESRD. The ESRD cohort includes patients age 67 and older; the MarketScan cohort includes all ESRD patients with fee-for-service coverage during the study period, and the Ingenix i3 cohort includes all ESRD patients under coverage with business type classified as commercial.

Figures 7.13–20 show the percentage of patients on specific drugs during the eight quarters prior to and the one quarter after ESRD initiation, based on CKD diagnosis codes. The cohort includes 2008 incident MarketScan and Ingenix i3 ESRD patients age 20–64. MarketScan patients have fee-for-service coverage and drug insurance during the nine quarters, while Ingenix i3 patients have coverage with business type classified as commercial during the same period.

Figures 7.21–22 and Table 7.a illustrate the percentage of patients on specific drugs prior to and after ESRD initiation, and use the same study cohort as Figures 7.13–20.

Chapter Eight Acute kidney injury  Top

In this chapter, patients with a hospitalization for acute kidney injury (AKI), or for AKI requiring dialysis (AKI-D) are identified from inpatient claims by the presence of ICD-9-CM code 584.x or by indication of dialysis through any of the following: ICD-9-CM procedure codes 39.95 and 54.98; ICD-9-CM diagnosis codes V45.1, V56.0, and V56.1; CPT codes 90935, 90937, 90945, and 90947; and revenue codes 0800–0809. Patients with ESRD diagnosed before the AKI hospitalization discharge are omitted, except as indicated. For patients with multiple AKI hospitalizations through the years, the first one in the time frame is counted. The event rate is estimated as the number of events per 1,000 patient years at risk.

Figure 8.1 displays the percentage of patients hospitalized for AKI or AKI-D in a given year. The cohort includes general Medicare patients age 66 or older on December 31 of the cohort year, continuously enrolled in Medicare inpatient/outpatient and physician/supplier coverage, with no HMO coverage, and who survive and are without ESRD in the cohort year.

Figure 8.2 shows the demographic characteristics of patients suffering AKI. The study cohort includes the general Medicare patients described for Figure 8.1 (Figure 8.2 uses the 2008 cohort), along with MarketScan and Ingenix i3 patients age 20–64 on December 31 of the cohort year who are enrolled in a fee-for-service plan.

Figures 8.3–7 use the same cohorts described for Figure 8.1. Figures 8.3–4 show rates per time at risk, while Figure 8.5 shows the type of dialysis used by hospitalized AKI-D patients. Modality is defined as follows: peritoneal dialysis, CPT codes 90945 or 90947 and 49420; continuous venous-to-venous hemodialysis (CVVHD), dialysis with CPT codes 90945 or 90947 but without 49420; intermittent hemodialysis (IHD), dialysis with CPT codes 90935 or 90937 and intermittent in the first three days; and daily hemodialysis (DHD), dialysis with CPT codes 90935 or 90937 and with three consecutive dialysis sessions in the first three days. To define modality, we first determine if there is any peritoneal dialysis during the period of the AKI event, and then look for continuous dialysis to identify hemodialysis or DHD. Those who are not identified by the above methods are categorized as having an unknown dialysis type. Figure 8.6 shows the percentage of hospitalized AKI patients who receive ACEs/ARBs or statins during the same year as their AKI, and Figure 8.7 illustrates the principle diagnosis that appears on AKI claims.

Figures 8.8–11 present hazard ratios for AKI hospitalization, adjusted for age, gender, and race. The study cohort includes 2007 general Medicare patients age 66 and older, along with 2007 MarketScan and Ingenix i3 patients age 20–64. Patients with ESRD before January 1, 2008, are excluded. Each patient is followed from this date to the earliest of death (Medicare patients only), ESRD diagnosis, change of enrollment, or December 31, 2008.

Figure 8.12 illustrates geographic variations in unadjusted rates of AKI and AKI-D in 2003 and 2008 for general Medicare patients. The cohort is constructed as in Figure 8.2, but is restricted to those residing in the 50 states and the District of Columbia.

Methods of identifying the type of physician visit for Figures 8.13–14 are the same as those described in the methods for Chapter Seven. In Figure 8.14, multiple physician claims for the same specialty during the same inpatient stay are counted only once.

Testing in Figures 8.15–16 is identified as follows: creatinine testing, HCPCS codes 80048, 80050, 80053, 80069, and 82565; urine protein testing: CPT codes 82042, 82043, 82044, and 84156.

Figure 8.17 examines the use of ACEIs/ARBs and statins before and after AKI hospitalization, and includes 2007 Medicare patients with Part D coverage, identified as in Figure 8.2.

Figures 8.18 and 8.20 demonstrate the probability of patients having a recurrent AKI hospitalization. The Kaplan-Meier method is used to calculate the cumulative unadjusted probability of testing during the one-year follow-up period.

Figure 8.19 displays changes in CKD status following an AKI hospitalization in 2007, based on CKD claims before and after the hospitalization. The cohort includes all Medicare patients age 66 or older on December 31, 2007. CKD claims are identified in the one year prior and one year following the AKI admission date, and CKD stage is defined with the method described above, under "identification of major comorbidities." ESRD is defined by the ESRD date.

Figure 8.21 shows the distribution of patients by CKD stage prior to an AKI hospitalization in 2007, along with discharge status and outcomes. Patients are from the 5 percent Medicare sample. CKD stage is obtained from 2007 claims prior to the admission date, and nephrologist care is determined from claims in the year following discharge. Creatinine testing during the three months after discharge, and albumin in the one year following discharge, are identified from claims using the method described for Chapter Three.

Chapter Nine Costs of chronic kidney disease  Top

The general Medicare point prevalent cohort used in Figures 9.1–4 includes persons age 65 and older who survive all of year one, are continuously enrolled in Medicare inpatient/outpatient and physician/supplier coverage for this period, are not enrolled in an HMO, and do not have ESRD during year one. Costs are aggregated for year two, with censoring at the earliest of death, development of ESRD, change in payor status, or the end of year two. Figure 9.2 also features the MarketScan point prevalent CKD population, constructed in a similar fashion, but limited to patients aged 50–64.

Figure 9.1 also illustrates estimated populations and costs from the 1 percent Taiwan National Health Insurance (NHI) dataset, which, like Medicare claims data, employs ICD-9-CM diagnosis to identify the presence of CKD and key comorbid conditions. Patients age 65 and older with CKD (without ESRD), CVD, or diabetes are determined from claims in year one, and costs are aggregated for calendar year two, 2008.

Figures 9.5–8 look at 2007 incident Medicare and MarketScan ESRD patients during the transition to ESRD. Medicare patients here are age 67 and older, with Medicare as primary payor for the entire transition period (six months before through six months after the initiation of renal replacement therapy), and not enrolled in a managed care program (HMO) during the transition period. The MarketScan patients include those younger than 65 and continuously enrolled in a fee-for-service plan for the entire transition period.

Costs are categorized in several ways throughout this chapter. For Figures 9.1, 9.12, and 9.18–20, and for Table 9.b, costs are simply total claims-based expenditures, while those in 9.2–4 and 9.9–11 are claims-based expenditures PPPY. Figures 9.5 and 9.20–21 display costs as PPPM claims-based totals, and Figures 9.13–17 show PPPM costs for Part D claims. Costs for Figures 9.6–8 are limited to inpatient claims, and expressed PPPM. Costs are further broken down for Table 9.a, using diagnosis-related groupings (DRGs) for inpatient claims; revenue codes, current procedural terminology (CPT) codes, and healthcare common procedure coding system (HCPCS) codes for outpatient claims; and CPT, HCPCS, provider specialty, and place of service codes for physician/supplier claims.

Using the point prevalent methodology described above, Figure 9.1 compares populations and costs in 2008 for Medicare patients (based on the 5 percent Medicare sample) and patients from the 1 percent random sample of the Taiwan National Health Insurance (NHI) population, while Figures 9.18–21 show expenditures for point prevalent populations (described above) drawn from these same sources. Figures 9.22–23 show overall and inpatient PPPM expenditures during the transition for Medicare and NHI patients initiating ESRD in 2007.

Important comorbidities (diabetes, CKD, and CHF) are determined for these cohorts from Medicare claims using a previously validated method, as described earlier in this appendix in the section "identification of major comorbidities." Costs are presented for the 1992–2007 cohorts. The cost year is always the year after the cohort year.

The MarketScan population includes patients age 50–64, and is constructed in the same fashion as that described for the Medicare population, requiring continuous enrollment in a fee-for-service health plan. Patients identified as having ESRD are excluded, and the cohorts are from 1999 to 2007.

Figures 9.9–17 and Table 9.b present Medicare Part D costs. Populations used in these figures are derived from the point prevalent Medicare population (described above), with the further restriction that each individual included in the population is enrolled in Part D for the full 12 months of the analysis year and has a qualifying diagnosis of CKD. Costs are estimated Medicare net pay, which is the sum of plan covered payments and low income subsidy payments. Costs do not include out of pocket expenditures. Table 9.b and Figure 9.12 show total expenditures, while the other figures use per person per month PPPM or PPPY expenditures.

In Figures 9.18–21 we again use data from the NHI dataset. To allow comparisons with Medicare data, the cohort includes only patients age 65 and older. Patient counts are estimated using the methods defined for Figure 9.1.

Figures 9.22–23 illustrate expenditures during the six months before and six months after initiation of dialysis among incident ESRD patients in the U.S. and Taiwan. Total and inpatient hospitalization costs PPPM are calculated for Medicare patients age 67 and older, MarketScan patients younger than 65, and NHI patients.

Reference tables

Tables B.1–6 present estimated point December 31 prevalent counts of the general Medicare non-ESRD population, based on the 5 percent Medicare sample.

Tables B.7–10 present estimated counts by age, gender, race, ethnicity, and comorbidity in the non-institutionalized U.S. population, using NHANES 1999–2006 data. CKD status is based on eGFR and ACR, and eGFR is estimated by the MDRD and CKD-EPI equations, using standardized serum creatinine as suggested by NCHS. Both diabetes and CHF are self-reported.

Tables K.1–5 present estimates of per person per year costs for general Medicare patients, also derived from the 5 percent Medicare sample. The cohorts include those who survive all of year one, are continuously enrolled with Medicare inpatient/outpatient and physician/supplier coverage, are not enrolled in a managed care program (HMO), and do not have ESRD during year one. Costs are aggregated for year two, with censoring at the earliest of death, development of ESRD, change in payor status, or the end of year two. Important comorbidities are determined for these cohorts from Medicare claims using a previously validated method, as described earlier in this appendix in the section on identification of major comorbidities. PPPY expenditures are presented for the 1992–2007 cohorts. The cost year is always the calendar year after the cohort year.