Chemistry Testing on Plasma Versus Serum Samples in Dialysis Patients: Clinical and Quality Improvement Implications.

Plasma samples collected in tubes containing separator gels have replaced serum samples for most chemistry tests in many hospital and commercial laboratories. Use of plasma samples for blood tests in the dialysis population eliminates delays in sample processing while waiting for clotting to complete, laboratory technical issues associated with fibrin formation, repeat sample collection, and patient care issues caused by delay of results because of incompletely clotted specimens. Additionally, a larger volume of plasma is produced than serum for the same amount of blood collected. Plasma samples are also acceptable for most chemical tests involved in the care of patients with ESRD. This information becomes very important when United States regulatory requirements for ESRD inadvertently limit the type of sample that can be used for government reporting, quality assessment, and value-based payment initiatives. In this narrative, we summarize the renal community experience and how the subsequent resolution of the acceptability of phosphorus levels measured from serum and plasma samples may have significant implications in the country's continued development of a value-based Medicare ESRD Quality Incentive Program.

The Glycemic Indices in Dialysis Evaluation (GIDE) study: Comparative measures of glycemic control in diabetic dialysis patients.

The validity of hemoglobin A1c (HgbA1c) is undergoing increasing scrutiny in the advanced CKD/ESRD (chronic kidney disease/end-stage renal disease) population, where it appears to be discordant from other glycemic indices. In the Glycemic Indices in Dialysis Evaluation (GIDE) Study, we sought to assess correlation of HgbA1c with casual glucose, glycated albumin, and serum fructosamine in a large group of diabetic patients on dialysis. From 26 dialysis facilities in the United States, 1758 diabetic patients (hemodialysis = 1476, peritoneal dialysis = 282) were enrolled in the first quarter of 2013. The distributions of HgbA1c and the other glycemic indices were analyzed. Intra-patient coefficients of variation and correlations among the four glycemic indices were determined. Patients with low HgbA1c values were both on higher erythropoietin (ESA) doses and more anemic. Serum glucose exhibited the highest intra-patient variability over a 3-month period; variability was modest among the other glycemic indices, and least with HgbA1c. Statistical analyses inclusive of all glycemic markers indicated modest to strong correlations. HgbA1c was more likely to be in the target range than glycated albumin or serum fructosamine, suggesting factors which may or may not be directly related to glycemic control, including anemia, ESA management, and iron administration, in interpreting HgbA1c values. These initial results from the GIDE Study clarify laboratory correlations among glycemic indices and add to concerns about reliance on HgbA1c in patients with diabetes and advanced kidney disease.

Sickle trait in African-American hemodialysis patients and higher erythropoiesis-stimulating agent dose.

African Americans require higher doses of erythropoiesis-stimulating agents (ESAs) during dialysis to manage anemia, but the influence of sickle cell trait and other hemoglobinopathy traits on anemia in dialysis patients has not been adequately evaluated. We performed a cross-sectional study of a large cohort of adult African-American hemodialysis patients in the United States to determine the prevalence of hemoglobinopathy traits and quantify their influence on ESA dosing. Laboratory and clinical data were obtained over 6 months in 2011. Among 5319 African-American patients, 542 (10.2%) patients had sickle cell trait, and 129 (2.4%) patients had hemoglobin C trait; no other hemoglobinopathy traits were present. Sickle cell trait was more common in this cohort than the general African-American population (10.2% versus 6.5%-8.7%, respectively, P<0.05). Among 5002 patients (10.3% sickle cell trait and 2.4% hemoglobin C trait) receiving ESAs, demographic and clinical variables were similar across groups, with achieved hemoglobin levels being nearly identical. Patients with hemoglobinopathy traits received higher median doses of ESA than patients with normal hemoglobin (4737.4 versus 4364.1 units/treatment, respectively, P=0.02). In multivariable analyses, hemoglobinopathy traits associated with 13.2% more ESA per treatment (P=0.001). Within subgroups, sickle cell trait patients received 13.2% (P=0.003) higher dose and hemoglobin C trait patients exhibited a similar difference (12.9%, P=0.12). Sensitivity analyses using weight-based dosing definitions and separate logistic regression models showed comparable associations. Our findings suggest that the presence of sickle cell trait and hemoglobin C trait may explain, at least in part, prior observations of greater ESA doses administered to African-American dialysis patients relative to Caucasian patients.

Serum fructosamine versus glycosylated hemoglobin as an index of glycemic control, hospitalization, and infection in diabetic hemodialysis patients.

Diabetes is the most common cause of end-stage renal disease and an important risk factor for morbidity and mortality in dialysis patients. Glycemic control, utilizing serial measurement of glycosylated hemoglobin (HbA1c), is generally recommended to limit end-organ damage, including cardiovascular morbidity and mortality. We, along with others, have previously suggested that HbA1c may not be a reliable measure of glycemic control in dialysis patients, and have therefore explored the use of serum fructosamine (SF) as an alternative marker. The objective of this study was to compare HbA1c levels with SF in monitoring glycemic control and associated morbidity (infection and hospitalization) in diabetic patients in a large urban hemodialysis (HD) center. We enrolled 100 diabetic HD patients and followed them up prospectively for 3 years. Data on demographics, as well as biochemical and clinical data, including hospitalizations and infections, were recorded. The mean age was 63 years. In all 54% were women and the majority were African Americans (72%). As expected, HbA1c and albumin-corrected fructosamine (AlbF) levels were highly correlated and both were significantly associated with serum glucose. AlbF, however, was more highly correlated with mean glucose values when less than 150 mg/dl and was a more useful predictor of morbidity. By univariate logistic regression and by Poisson regression analysis, AlbF, but not HbA1c, was a significant predictor of hospitalization. Additionally, in patients dialyzed by arteriovenous (AV) access (that is, excluding those dialyzed via vascular catheters), AlbF, but not HbA1c, was a significant predictor of infection. In conclusion, AlbF is as reliable a marker as HbA1c for glycemic control in diabetic patients on HD, and may be advantageous for patients with serum glucose in a desirable therapeutic range (<150 mg/dl). In addition, AlbF, but not HbA1c, is associated with morbidity (hospitalizations and infections) in diabetic patients on HD.