Serum monoclonal immunoglobulin light-chain detection differs between immunofixation electrophoresis methods in patients with AL amyloidosis.

Serum immunofixation electrophoresis (IFE) is often performed for screening monoclonal proteins (M proteins) in immunoglobulin light-chain amyloidosis (AL amyloidosis). However, the performance of serum IFE for detecting M protein in AL amyloidosis patients is often insufficient. In this study, we examined the detection rate of serum M protein in newly diagnosed AL amyloidosis patients and analyzed differences in M protein detection between IFE methods. Among 60 patients newly diagnosed with AL amyloidosis, 22 had undetectable serum M protein by IFE with the Epalyzer2 system. Samples with undetectable M protein had significantly lower involved serum-free light-chain (iFLC) and a smaller difference between involved and uninvolved serum-free light-chain (dFLC) values than samples with IFE-detectable monoclonal light chains. When samples that tested negative for M protein by the Epalyzer2 system were retested by IFE with the HYDRASYS 2 system, 50% had IFE-detectable monoclonal light chains. The IFE system and reagents used may affect serum monoclonal immunoglobulin light-chain detection in AL amyloidosis patients, especially those with low iFLC or low dFLC samples. More attention should be paid to the performance of IFE systems, since it may affect the diagnostic and therapeutic evaluation of AL amyloidosis patients.