Background: Understanding the clinical variability of hemoglobin measurements in epoetin-treated hemodialysis patients is important, particularly when this therapy is aimed at maintaining patient hemoglobin levels within a narrow range, such as the 11 to 12 g/dL range recommended in National Kidney Foundation Kidney Dialysis Outcomes Quality Initiative (NKF-K/DOQI) guidelines. This study examines hemoglobin variability under conditions of standard clinical practice in epoetin-treated hemodialysis patients.
Methods: We studied 987 hemodialysis patients participating in an observational retrospective study that evaluated anemia management practices from October 1, 1996 to December 31, 1997 at 11 United States dialysis centers that were randomly selected from a pool of nearly all United States dialysis facilities. Each participating facility maintained its own anemia management protocols without specific anemia management recommendations or interventions made as part of this study. Hemoglobin variability was determined by calculating the 1-month and 2- to 6-month rolling average hemoglobin for each patient. The range of mean hemoglobin values that included the middle 50% (25th to 75th percentile), 80% (10th to 90th percentile), and 90% (5th to 95th percentile) of values were determined. The hemoglobin ranges that included 1 standard deviation (SD) (67%) of the study values and 2 SD (95%) of the study values for each time period were calculated.
Results: The mean hemoglobin was between 10.9 and 11.2 g/dL throughout the study. The hemoglobin range encompassing 50%, 80%, and 90% of values from a single month was 1.7, 3.3, and 4.4 g/dL, respectively. A progressive narrowing in the range of hemoglobin values encompassed by each percentile grouping (i.e., hemoglobin variability) was observed as longer rolling intervals were averaged. The hemoglobin range within the 25th to 75th percentile was 1.7 g/dL using single-month hemoglobin values and 1.1 g/dL using a 6-month rolling average. The range of hemoglobin values that encompassed 90% of patients was 4.4 g/dL using single-month values, 3.7 g/dL using 3-month rolling averages, and 3.2 g/dL using 6-month rolling averages. Fewer than 50% of patients had hemoglobin values within the 1.0 g/dL NKF-K/DOQI recommended range, even when a 6-month rolling average was applied. When hemoglobin values were measured for 1 month, 1 SD was 1.4 g/dL; for the 3-month rolling average, 1 SD was 1.1 g/dL; and for the 4-, 5-, and 6-month rolling averages, 1 SD was 1.0 g/dL. Greater hemoglobin variability correlated with higher mean corpuscular hemoglobin (P = 0.003) and serum ferritin (P = 0.047), and inversely correlated with age (P = 0.006) and serum albumin (P = 0.0001).
Conclusion: Substantial variability occurs in hemoglobin values in epoetin-treated hemodialysis patients. The NKF-K/DOQI recommended hemoglobin range appears to be too narrow in clinical practice. Expanding the target range and use of rolling average hemoglobin intervals of 3 to 6 months as a clinical and quality assurance measure avoids clinical variability inherent with the use of isolated hemoglobin values or single-month hemoglobin averages.