A study of the use of free light chains to improve the interpretation of capillary electrophoresis

Abstract

Background. Since April 2007 the laboratory has offered a diagnostic and monitoring service for patients with Myeloma and related diseases. The tests available when the service began were serum Capillary Zone Electro - phoresis (CZE), Immunotyping (IFE) and urine gel electrophoresis (UPE). In response to clinical demand serum free light chain (FLC) assays were added in 2008. Aims. To identify situations where further tests are required to interpret Capillary Zone Electrophoresis. Methods. All requests received from 1st April 2009 to 31st May 2010 were assessed and results obtained for each of the three tests were compared. Results. In total, 6,648 CZE, 1,347 UPE and 951 FLCs were assayed. Of the CZEs, 18% had a paraprotein, with 28% of these (334 patients) having no previous history of Myeloma. The FLCs were analysed and the results tabulated against the CZE results (Table 1). 6% of all CZE requests were reported as abnormal but with no band identified. This group included samples with Beta/Gamma bridging, small peaks in the gamma and irregular patterns in the Beta region which cannot be conclusively identified by a combination of CZE and IFE. Of the UPEs, 50 abnormal bands were detected (4%). Three patients had an abnormal band in the urine and no abnormalities detected by CZE or FLCs. One patient had an 8.5 g/L paraprotein nine months later but neither remaining patient had a subsequent sample analysed. Summary/Conclusion. CZE combined with IFE allows identification of paraprotein bands down to 2 g/L when they migrate in the gamma region. FLCs are essential for the identification of patients with paraproteins which run in the beta region and for patients with hypogammaglobulinaemia