Relative contributions of inflammation and inadequate protein intake to hypoalbuminemia in patients on maintenance hemodialysis

Abstract

PURPOSE: Serum albumin is one of the strongest mortality predictors in maintenance hemodialysis (MHD) patients. Yet, the degree to which serum albumin represents dietary protein intake or an inflammatory state, among others, is not clear. We hypothesize that these inadequate protein intake and inflammation contribute somewhat equally to hypoalbuminemia. METHODS: In a cross-sectional analysis, we examined correlates of low serum albumin, <3.8 g/dL, in 812 MHD patients in whom interleukin-6 (IL-6) and normalized protein nitrogen appearance (nPNA), also known as normalized protein catabolic rate (nPCR), were also measured. Logistic regression estimated odds ratios were employed, and spline models were plotted to examine the likelihood of relatively low serum albumin <3.8 g/dL. RESULTS: Mean age (+/-SD) of patients was 54 +/- 15 years; 53 % of patients were men, 50 % Hispanic, 31 % African-American, and 55 % diabetic. The mean dialysis vintage was 31 +/- 34 months (median: 19, inter-quartile range: 7-44 months). The baseline serum albumin, averaged over a 3-month period (mean +/- SD), was 3.88 +/- 0.38 g/mL. The unadjusted correlation coefficients of l IL-6 and nPNA with serum albumin were -0.36 and +0.20, respectively (p < 0.001 for each comparison). The likelihood for an albumin <3.8 gr/dL increased linearly with decreasing nPNA and rising serum IL-6. This trend was steeper with increasing serum IL-6 up to a concentration of 30 ng/mL. CONCLUSIONS: Both low protein intakes and a high state of inflammation are associated with low serum albumin in MHD patients.