Assessment of M-protein quantification using capillary electrophoresis and immunosubtraction-based integration in clinical samples with low M-protein concentrations.

Abstract

OBJECTIVES:

Quantification of monoclonal protein (M-protein) by serum protein electrophoresis (SPE) is indispensable for diagnosing and monitoring monoclonal gammopathies. However, quantification of small and beta migrating M-proteins is challenging because of overlapping non-immunoglobulin and/or polyclonal immunoglobulin protein fractions. We compared a new integration method based on immunosubtraction (IS-CE) using capillary zone electrophoresis (CZE) against the routine method, which includes a combination of perpendicular drop (0.4%), corrected perpendicular drop (1%) and tangent skimming (98.5%).

DESIGN & METHODS:

The proposed method of M-protein quantification involves calculating the difference in area under the curve between the SPE and a class-specific IS-CE trace. We analyzed the difference in estimated M-protein concentrations obtained with the new method and routine integration methods using 913 samples. For IgA M-proteins at < 10 g/L, the estimated M-protein concentrations were compared with the total IgA concentration.

RESULTS:

The median M-protein concentration of 913 consecutive samples was 6.2 g/L (IQR 2.1-14.3 g/L). The median and median % difference between the two integration methods was 0.68 g/L (IQR 0.01-1.55 g/L) and 10.9% (IQR 0.18-38.7%), showing a larger estimated M-protein concentration with the new method. More than 25% difference was observed in 38% of the samples and was associated with lower total protein concentration, lower M-protein concentration, IgA and IgM heavy chain isotypes, and beta- or beta-gamma migration. When 161 samples with IgA M-protein < 10 g/L were compared against total IgA concentration, the median bias of the new method was smaller compared to that of the existing method (-0.95 g/L vs. -1.3 g/L, P < 0.0001).

CONCLUSIONS:

The use of IS based integration using CZE and IS-CE is promising especially for small and beta migrating M-proteins.

• Authors: Hanwool Cho, Jin Jung, Hyojin Chae, Jeong Joong Lee, Myungshin Kim, Eun-Jee Oh, Yonggoo Kim, Chang-Ki Min
• Journal: Clinical biochemistry (Clin Biochem) Vol. 107 Pg. 7-12 (Sep 2022) ISSN: 1873-2933 [Electronic] United States
• PMID: 35660484 (Publication Type: Journal Article)
• Copyright: Copyright © 2022. Published by Elsevier Inc.

Chemical References

• Antibodies, Monoclonal
• Immunoglobulin A
• Immunoglobulin M

Topics

• Antibodies, Monoclonal
• Electrophoresis, Capillary (methods)
• Humans
• Immunoglobulin A
• Immunoglobulin M
• Paraproteinemias (diagnosis)