IgMκ-IgMλ pair quantitation in the clinical laboratory practice

Area of Science:

• Immunology
• Clinical Chemistry
• Hematology

Background:

• The Hevylite® assay quantifies immunoglobulin classes, including IgM bound to light chains.
• This aids in distinguishing immunoglobulins involved and uninvolved in plasma cell disorders.

Purpose of the Study:

• To compare the IgM Hevylite® (IgM-HLC) assay with conventional methods for monitoring IgM plasma cell disorders.
• To evaluate the diagnostic utility of IgM-HLC in routine laboratory practice.

Main Methods:

• Serum samples (n=122) from 50 patients with IgM monoclonal protein were analyzed.
• Methods included IgM Hevylite® (HLC) assay, Capillary Electoresis (CE), Immunofixation (IFE), serum Free Light Chain (FLC) assay, and total IgM measurements.

Main Results:

• IgM monoclonal protein was detected by IFE in 85/122 samples.
• The HLC ratio was altered in 36/85 positive samples, while FLC was altered in 4/85.
• Out of 37 IFE-negative samples, 24 had normal HLC and FLC ratios.

Conclusions:

• The IgM Hevylite assay provides valuable information on IgM monoclonal disease evolution.
• Partial overlap between HLC and FLC assays suggests complementary roles in monitoring.
• This assay may improve routine laboratory practice for diagnosing and managing IgM monoclonal disorders.