Association of Monoclonal Gammopathy with Progression to ESKD among US Veterans.

Background And Objectives: Whether patients with monoclonal protein are at a higher risk for progression of kidney disease is not known. The goal of this study was to measure the association of monoclonal protein with progression to ESKD.

Design, Setting, Participants, & Measurements: This was a retrospective cohort study of 2,156,317 patients who underwent serum creatinine testing between October 1, 2000 and September 30, 2001 at a Department of Veterans Affairs medical center, among whom 21,898 had paraprotein testing within 1 year before or after cohort entry. Progression to ESKD was measured using linked data from the US Renal Data System.

Results: Overall, 1,741,707 cohort members had an eGFR≥60 ml/min per 1.73 m, 283,988 had an eGFR of 45-59 ml/min per 1.73 m, 103,123 had an eGFR of 30-44 ml/min per 1.73 m and 27,499 had an eGFR of 15-29 ml/min per 1.73 m. The crude incidence of ESKD ranged from 0.7 to 80 per 1000 person-years from the highest to lowest eGFR category. Patients with low versus preserved eGFR were more likely to be tested for monoclonal protein but no more likely to have a positive test result. In adjusted analyses, a positive versus negative test result was associated with a higher risk of ESKD among patients with an eGFR≥60 ml/min per 1.73 m (hazard ratio, 1.67; 95% confidence interval, 1.22 to 2.29) and those with an eGFR of 15-29 ml/min per 1.73 m (hazard ratio, 1.38; 95% confidence interval, 1.07 to 1.77), but not among those with an eGFR of 30-59 ml/min per 1.73 m Progression to ESKD was attributed to a monoclonal process in 21 out of 76 versus seven out of 174 patients with monoclonal protein and preserved versus severely reduced eGFR at cohort entry.

Conclusions: The detection of monoclonal protein provides little information on ESKD risk for most patients with a low eGFR. Further study is required to better understand factors contributing to a positive association of monoclonal protein with ESKD risk in patients with preserved and severely reduced levels of eGFR.