The Gamma Gap Predicts All-Cause Mortality in Chronic Dialysis Patients

INTRODUCTION: The gamma gap (γ-gap) represents the total serum protein concentration minus the albumin concentration. The main aim of this study was to test whether the gamma gap is a predictor of mortality and whether it is associated with other predictors of mortality in chronic hemodialysis patients (CHPs). MATERIALS AND METHODS: We studied a cohort of 100 CHPs with a mean age of 59 ± 12.3 years with duration of dialysis 6.5 ± 4.7 years. Serum proteins were determined by electrophoresis. The association of the gamma gap with serum C-reactive protein (CRP), fibrinogen and albumin concentration was evaluated for correlation. Cox regression analysis was used to identify the predictors of mortality. RESULTS: The γ-gap correlates positively with CRP (r = 0.247, P = 0.013) and fibrinogen (r = 0.239, P = 0.016), and inversely with albumin (r = -0.430, P < 0.0001). The regression coefficients (b) and Exp (b) hazard ratio coefficients of covariates in Cox-regression survival analysis in all-cause outcomes were: b = 0.1486, Exp (b) = 1.1602 (P < 0.0001); b = 0.0655, Exp (b) = 1.0677 (P < 0.0015) and b = -0.118, Exp (b) = 0.8887 (P < 0.0009), for γ-gap, CRP and albumin, respectively. CONCLUSIONS: In patients on chronic hemodialysis, the gamma gap, along with serum albumin and CRP levels, is an independent predictor of mortality. Gamma gap levels correlate directly with serum CRP and fibrinogen levels and inversely with serum albumin levels.