Monoclonal Gammopathy as a Determinant of Adverse Outcomes in Patients with Chronic Kidney Disease.

Elevated serum free light chain (sFLC) concentrations are associated with glomerular and tubulointerstitial disease. We have analyzed a cohort of patients with chronic kidney disease (CKD) to determine the relationship between sFLC and clinical outcomes. 369 patients from the renal clinics at the Queen Elizabeth hospital in Birmingham were followed for a period of 8 years. We reviewed renal outcomes and all cause mortality over this period. sFLC levels were measured on baseline serum samples using a nephelometric immunoassay (The Binding Site Ltd.). The CKD patients had mean sFLC concentrations significantly higher than the normal population (kappa: 77 vs. 8.4mg/L p<0.0001; lambda: 94.7 vs. 13.4mg/L p<0.03). 65 patients (18%) had abnormal sFLC ratios suggesting clonal production of sFLC. There were 270 endpoints during follow-up (106 deaths and 164 end stage renal failures). By Kaplan Meier survival analysis an abnormal sFLC ratio is significantly associated with a worse composite outcome (p<0.02), with the dominant factor being the progression of renal impairment to end stage disease. This is the first study to assess if an abnormal sFLC ratio is predictive of outcomes in patients with CKD. These findings provide the basis for further work to evaluate whether monoclonal FLCs are prognostic of a worse outcome in patients with CKD.