Use of serum free light chain analysis and urine protein electrophoresis for detection of monoclonal gammopathies

Background: Serum free light chain (FLC) analysis is used in the prognostic assessment and monitoring of patients with monoclonal gammopathies (MG). Its use in detection of MG is less widespread despite good sensitivity for diseases poorly detected by serum protein electrophoresis (SPE), e.g., FLC disease and AL amyloidosis. FLC analysis may facilitate earlier diagnosis in these diseases. However, if replacing urine protein electrophoresis (UPE) in an initial screening algorithm, this must be balanced against any loss of detection of Bence Jones proteinuria (BJP). Methods: We assessed the effect of replacing UPE with FLC. Sensitivity of FLC for BJP was assessed in 126 clinical cases where UPE and FLC analyses were performed. Impact on disease detection was assessed from 753 patient sera tested by SPE and FLC and 128 patients matched associated urine samples. Results: Sensitivity of FLC for BJP was 98%. Use of FLC in routine testing increased the number of MG detected by 7%. Conclusions: Using FLC alongside or in place of UPE can give clinical benefit through earlier diagnosis and hence treatment earlier in the patients' disease.