Serum Polyclonal Immunoglobulin Free Light Chain Levels Predict Mortality in People With Chronic Kidney Disease

Objective: To determine whether elevated serum polyclonal free light chain (FLC) levels predict mortality in a population of individuals with chronic kidney disease (CKD). Patients and Methods: From January 2, 2006, through July 31, 2007, we recruited a cohort of 848 people with CKD who were not receiving renal replacement therapy and did not have monoclonal gammopathy. We measured serum kappa FLC and lambda FLC isotype levels to determine combined FLC (cFLC) levels. The cohort was prospectively followed up for a median of 63 months (interquartile range, 0-93 months). Cox regression analysis was performed to determine variables predictive of mortality. Results: High cFLC levels were an independent risk factor for death (hazard ratio [HR], 2.71; 95% CI, 1.98-3.70; P<.001). Other independent risk factors were age ( HR, 1.79; 95% CI, 1.52-2.10; P<.001), South Asian ethnicity (HR, 0.33; 95% CI, 0.14-0.64; P=.02), preexisting cardiovascular disease (HR, 1.59; 95% CI, 1.09-2.31; P=.02), and high-sensitivity C-reactive protein (HR, 1.13; 95% CI, 1.00-1.28; P=.04). Neither estimated glomerular filtration rate nor albuminuria was an independent risk factor for death. Conclusion: High cFLC levels independently predict mortality in people with CKD. (C) 2014 Mayo Foundation for Medical Education and Research.