Capillary electrophoresis/immunosubtraction as a better alternative to immunofixation for detecting and immunotyping serum monoclonal proteins in patients with immunoglobulin light chain (AL) amyloidosis.

Capillary electrophoresis/immunosubtraction (CE/IS) is a simple method for detecting and immunotyping serum or urine monoclonal proteins. To our knowledge, there are no previous reports of the use of CE/IS for characterizing patients with Immunoglobulin light chain (AL) amyloidosis, and there are no convincing data available to compare CE/IS with serum immunofixation electrophoresis (IFE) and free light chain (FLC) assay. The aim of this study was to evaluate the clinical utility of CE/IS in patients with AL amyloidosis as a diagnostic accuracy study. This study included 50 patients with AL amyloidosis (17 newly diagnosed and 33 undergoing treatment). Serum IFE identified monoclonal proteins in 15/50 (30%) of all cases and in 7/17 (41%) of newly diagnosed cases. CE/IS identified monoclonal proteins in 16/50 (32%) of all cases and in 7/17 (41%) of newly diagnosed cases. The FLC assay detected an abnormal ratio of kappa and lambda light chains in 26/50 (52%) of all cases and in 15/17 (88%) of newly diagnosed cases. IFE and CE/IS combined with FLC assay identified monoclonal proteins more sensitive than IFE alone and CE/IS alone, in newly diagnosed patients (p = 0.002 and 0.002, respectively) and in patients undergoing treatment (p = 0.031 and 0.016, respectively). CE/IS is an acceptable alternative to IFE.