The value of serum immunoglobulin free light chain assessment in patients with monoclonal gammopathies and acute renal failure

Immunoglobulin free light chain (FLC) abnormalities are common in patients with monoclonal gammopathies and the kidneys are the most affected organs. Immunoassays that provide quantitative measurement of FLC in serum indicate monoclonal FLC production based on the presence of an abnormal FLC kappa:lambda (κ:λ) ratio. The aim of this study was to assess the utility of serum FLC measurement as a diagnostic tool for detecting plasma cell dyscrasias in comparison to standard assays, and to ascertain its sensitivity and specificity in patients with acute renal failure (ARF). Sera from 82 patients with ARF were assessed using serum protein electrophoresis (SPE), serum immunofixation electrophoresis (SIFE), and FLC measurement. The sensitivity and specificity of the FLC ratio in identifying which ARF patients had multiple myeloma (MM) was compared to those of SPE and SIFE. Among the 82 patients with ARF, 7 were diagnosed as MM using SPE, SIFE, and bone marrow biopsy techniques. In total, 8 patients did not have a FLC κ:λ ratio that was within the published reference range (0:26-1:65); the FLC κ:λ ratio based on FLC measurement had a specificity of 96% and sensitivity of 71%, and positive and negative predictive values of 62.9% and 97.3%, respectively, for the diagnosis of MM. The sensitivity and specificity of the FLC κ:λ ratio for diagnosing MM in patients that presented with ARF were lower than those of SPE and SIFE. To further delineate the utility of the FLC κ:λ ratio additional prospective, well-designed large-scale studies are needed. None declared.