Automated detection of free monoclonal light chains by enhanced-sensitivity modified immunofixation electrophoresis with antisera against free light chains.

Introduction: About one-third of multiple myelomas produce excess free monoclonal light chains. Detection of monoclonal light chains is important for diagnosis, prognosis, and monitoring of such lesions. A previously described method for detection of monoclonal light chains in serum required multiple manual wash steps. Even though the method has sensitivity similar to that of mass spectrometry, the manual wash steps were a hindrance to the method's widespread use.

Methods: To mitigate the laborious nature of the previous method, the SPIFE Nexus instrument (Helena Laboratories) was modified to automate the sample application, electrophoretic separation, antibody application, washing and blotting steps needed for removal of background proteins. Background noise was mitigated by modifying the wash buffer by adding a detergent. This revised automated electrophoresis protocol was tested in parallel with the previously described method.

Results: The sensitivity and specificity of the modified method using antisera to free light chains from 2 sources was comparable to the parameters of the previously described method without the need for manual manipulation.

Discussion: The automated protocol employing the SPIFE Nexus instrument and incorporating antisera to free light chains is suitable for routine use in clinical laboratories in an automated, enhanced-sensitivity assay for monoclonal light chains with no need for manual manipulation.