A Study on Free Light Chain Assay and Serum Immunofixation Electrophoresis for the Diagnosis of Monoclonal Gammopathies.

Demonstration of monoclonal immunoglobulin molecule in serum forms the mainstay in the diagnosis of monoclonal gammopathies. The major tests that help in this regard are serum protein electrophoresis (SPEP), serum immunofixation electrophoresis (sIFE) and serum free light chain assay (sFLC). Our objectives were to study the accuracy of sFLC and sIFE in the diagnosis of monoclonal gammopathies and also to study the role of combination of SPEP + sIFE + sFLC in the diagnosis of the same. 46 patients who attended the hemato-oncology clinic with signs and symptoms suggestive of monoclonal gammopathy were enrolled in this study. SPEP, sIFE, sFLC and pre-treatment serum beta-2 microglobulin levels were analysed among the study population. Both SPEP and sIFE were performed in the Interlab Genios fully automated machine. Serum beta-2 microglobulin and sFLC were estimated by immunoturbidimetry in Beckman Coulter AU 2700 analyzer. The accuracy of sIFE came to be 80% with respect to sFLC assay. Sensitivity, specificity, positive and negative predictive value of sIFE with respect to sFLC were 81.3, 78.6, 89.7 and 64.7% respectively. It was observed that a combination panel of SPEP + sIFE + sFLC could detect all the cases of myeloma included in this study. Further testing in large samples is required for generalising the findings of this study. The pre-treatment beta-2 microglobulin levels were significantly higher in the group which was positive for myeloma. A combination panel of SPEP + sIFE + sFLC prove to be more useful than individual tests for the detection of myeloma.