Relationship between Clinical Performance Measures and Outcomes among Patients Receiving Long-Term Hemodialysis

Context Several intermediate outcomes are used to evaluate care in hemodialysis programs, but the relationship between these measures and patient outcomes is uncertain. Contribution The authors studied 4 intermediate outcome measures (anemia, serum albumin level, functioning vascular access, and dialysis adequacy) in a 5% random sample of all U.S. patients receiving long-term hemodialysis. Annual mortality rates in patients who met 0, 1, 2, 3, or 4 quality measures were 29%, 25%, 21%, 14%, and 7%, respectively. Cautions This study was unable to determine whether failure to meet an outcome measure was due to patient factors, such as severity of illness, or because of poor-quality care. Implications Failure to meet hemodialysis quality measures is associated with increased mortality and hospitalization rates. The Editors Mortality rates among patients with end-stage renal disease (ESRD) in the United States have declined during the past 2 decades despite increases in the age and prevalence of diabetes in this population (1). The improvements in survival are not uniformly distributed across patients with differing durations of long-term dialysis therapy. Mortality rates have declined by 22% during the first 2 years after renal replacement therapy and by 15% during the next 3 years and have actually increased for patients surviving longer than 5 years (1). Despite these improvements in early survival, mortality rates remain quite high among patients with ESRD who are receiving hemodialysis, and 212 of every 1000 patients die annually. It is important to identify potentially modifiable risk factors for the persistently high mortality rates among U.S. patients with ESRD. The quality of care provided after the onset of renal replacement therapy provides one example of a set of modifiable risk factors. In 1997, the National Kidney Foundation developed quality-of-care indicators as part of the Dialysis Outcomes Quality Initiative (DOQI). These indicators were modified by the Centers for Medicare & Medicaid Services (CMS) ESRD Clinical Performance Measures Project (formerly known as the ESRD Core Indicators Project). Increased adequacy of hemodialysis and control of anemia have been shown to be associated with improved survival and quality of life among patients with ESRD (24). During the past decade, there has been a statistically significant improvement in the adequacy of dialysis as measured by Kt/V urea and in anemia management, which was fostered and documented by the CMS Clinical Performance Measures Project (5). Most studies that have examined the association between the quality of care of patients with ESRD and subsequent risk for death have used single measures of the quality of care provided to patients receiving dialysis (613). This approach fails to account for the possibility that achieving certain thresholds for multiple care processes is associated with less hospitalization and improvements in patient survival. We have tested this hypothesis using data from the ESRD Clinical Performance Measures Project to determine the association between hospitalization and mortality rates and meeting multiple guidelines for care delivered to patients receiving chronic hemodialysis. Methods Study Design and Sample Selection Detailed information about CMS's ESRD Clinical Performance Measures Project has previously been published (5). In brief, a random sample of Medicare-eligible adults receiving in-center hemodialysis stratified by the 18 ESRD Networks is selected each year from a census of patients with ESRD. The ESRD Networks are regional organizations contracted by CMS to perform quality oversight activities to ensure the appropriateness of services and quality of services for patients receiving dialysis. Patients were eligible for inclusion in the sample for each year of the study if they were at least 18 years of age as of 1 October of the previous year (for example, 1 October 1998 for study year 1999), were receiving in-center hemodialysis, and were alive on 31 December of the previous year. Clinical information was obtained on the selected patients for October to December of the year before the patient was chosen for the study. If a patient was randomly selected for more than 1 study year, then only the earlier year in which the patient was included in these samples was used for analytic purposes. For this analysis, data were analyzed for study years 1999 and 2000. Data Collection In May of each study year, the ESRD Networks sent a 3-page data collection form to approximately 2700 facilities. These facilities selected 1 or more patients for the sample. The median number of patients sampled per center was 2, and the number of patients sampled at an individual dialysis center ranged from 1 to 27; the 25th and 75th percentiles were 1 and 4 patients, respectively. Available patient information included sex, age, race (white, black, Asian or Pacific Islander, Native American or Alaska native, and other or unknown), Hispanic ethnicity, the primary cause of ESRD, and number of years that the patient received dialysis. In June of each study year, dialysis facility staff abstracted patient data from medical records for October to December of the previous year, including the patient's height, first documented blood urea nitrogen concentration before and after dialysis, weight before and after dialysis, dialysis session length, type of vascular access, hemoglobin value, and serum albumin value (bromcresol green or bromcresol purple laboratory methods). Completed forms were returned to the appropriate ESRD Network office where data were reviewed and entered into a computerized database. The Networks forwarded data to CMS for aggregation and analysis. Data regarding comorbid conditions were obtained by merging the ESRD Clinical Performance Measures database with data from CMS Form 2728 (Medical Evidence Form). This form provides additional clinical information on each patient at the initiation of dialysis. Specifically, the presence or absence of each of the following conditions was ascertained at the initiation of dialysis: congestive heart failure; ischemic heart disease; coronary artery disease; myocardial infarction; cardiac arrest; cardiac dysrhythmia; pericarditis; cerebrovascular disease, cerebrovascular accident, or transient ischemic attack; peripheral vascular disease; history of hypertension; diabetes mellitus (primary or contributing); diabetes mellitus and current use of insulin; chronic obstructive pulmonary disease; tobacco use (current smoker); malignant neoplasm or cancer; alcohol dependence; drug dependence; HIV-positive status; AIDS; inability to ambulate; and inability to transfer. Hospitalization information (all-cause hospitalization and 1 hospital admission during the follow-up period) was obtained from the U.S. Renal Data System's (USRDS) Hospitalization Standard Analytic File; dates of death, censoring information, and withdrawal from dialysis were obtained from the USRDS's Patients Standard Analytic File. Hospitalizations and dates of death were subsequently linked to the clinical information in the ESRD Clinical Performance Measures data file. Statistical Analysis The following intermediate outcomes or clinical measure targets were examined: mean Kt/V urea value of 1.2 or greater, mean hemoglobin value of 110 g/L or greater, use of an arteriovenous fistula for vascular access, and mean serum albumin value of 40 g/L or greater or 37 g/L or greater by the bromcresol green or bromcresol purple laboratory methods, respectively. In calculating mean values for Kt/V urea, hemoglobin, and serum albumin, all available reported data were used. If a value was missing for 1 of the study months, the mean value was calculated by averaging the 2 values over the 3-month study period. If values were missing for 2 of the 3 months, the available value became the mean value for that patient. For calculating rates of arteriovenous fistula use, patients with missing data were excluded from the denominator. Associations of group classification with the clinical measure targets were tested by the chi-square test, the 2-tailed Student t-test, and hierarchical analysis of variance. A 2-tailed P value less than 0.01 was considered statistically significant. Racial categorization was restricted to black and white only because of the small numbers of patients in other racial groups. Comorbid conditions were categorized as cardiovascular or noncardiovascular for subsequent analyses. Cardiovascular comorbid conditions included cardiac arrest, congestive heart failure, cerebrovascular disease, cardiac dysrhythmia, pericarditis, peripheral vascular disease, ischemic heart disease, and myocardial infarction. Noncardiovascular comorbid conditions included alcohol dependence, cancer, drug dependence, HIV infection, AIDS, inability to ambulate, inability to transfer, chronic obstructive pulmonary disease, and tobacco use. If a comorbid condition was not indicated on the Medical Evidence Form, then we assumed it was not present for the purposes of this analysis. To determine whether meeting 1 or more clinical measure targets was associated with hospitalization or death during the 12 months after the end of the study period, separate multivariable Cox proportional hazards modeling was performed. In addition to the number of clinical measure targets that were met, factors that were entered into the models included sex, race (black and white only), Hispanic ethnicity, age, years of dialysis, diabetes mellitus as the cause of ESRD compared with other causes combined, mean body mass index (weight in kilograms divided by the square of the height in meters) after dialysis, and preexisting cardiovascular and noncardiovascular comorbid conditions. Patients were censored at the time of transplantation, when they were switched to peritoneal dialysis, or when they were lost to follow-up for the Cox proportional hazards modeling analyses. All facto