Screening Method for M-Proteins in Serum Using Nanobody Enrichment Coupled to MALDI-TOF Mass Spectrometry.

Abstract

BACKGROUND:

Current recommendations for screening for monoclonal gammopathies include serum protein electrophoresis (PEL), imunofixation electrophoresis (IFE), and free light chain (FLC) ratios to identify or rule out an M-protein. The aim of this study was to examine the feasibility of an assay based on immunoenrichment and MALDI-TOF-MS (MASS-SCREEN) to qualitatively screen for M-proteins.

METHODS:

Serum from 556 patients previously screened for M-proteins by PEL and IFE were immunopurified using a κ/λ-specific nanobody bead mixture. Following purification, light chains (LC) were released from their heavy chains by reduction. MALDI-TOF analysis was performed and the mass-to-charge LC distributions were visually examined for the presence of an M-protein by both unblinded and blinded analysts.

RESULTS:

In unblinded analysis, MASS-SCREEN detected 100% of the PEL-positive samples with an analytical sensitivity and specificity of 96% and 81% using IFE positivity as the standard. In a blinded analysis using 6 different laboratory personnel, consensus was reached in 92% of the samples. Overall analytical sensitivity and specificity were reduced to 92% and 80%, respectively. FLC ratios were found to be abnormal in 28% of MASS-SCREEN-negative samples, suggesting FLC measurements need to be considered in screening.

CONCLUSIONS:

MASS-SCREEN could replace PEL in a panel that would include FLC measurements. Further studies and method development should be performed to validate the clinical sensitivity and specificity and to determine if this panel will suffice as a general screen for monoclonal proteins.

• Authors: Mindy C Kohlhagen, David R Barnidge, John R Mills, Joshua Stoner, Kari M Gurtner, Andrea M Liptac, Denise I Lofgren, Patrick M Vanderboom, Angela Dispenzieri, Jerry A Katzmann, Maria A V Willrich, Melissa R Snyder, David L Murray
• Journal: Clinical chemistry (Clin Chem) Vol. 62 Issue 10 Pg. 1345-52 (10 2016) ISSN: 1530-8561 [Electronic] England
• PMID: 27515443 (Publication Type: Journal Article)
• Copyright: © 2016 American Association for Clinical Chemistry.

Chemical References

• Antibodies, Monoclonal
• Immunoglobulin Light Chains

Topics

• Antibodies, Monoclonal (blood, immunology)
• Humans
• Immunoglobulin Light Chains (blood, immunology)
• Nanoparticles (chemistry)
• Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization