Quantification by Ultrafiltration and Immunofixation Electrophoresis Testing for Monoclonal Serum Free Light Chains

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OBJECTIVE: Measurement of monoclonal immunoglobulins is a reliable estimate of the plasma cell tumor mass. About 15% of plasma cell myelomas secrete light chains only. The concentration of serum free light chains is insufficient evidence of the monoclonal light chain burden. A sensitive quantitative estimate of serum free monoclonal light chains could be useful for monitoring patients with light chain myeloma. We describe such an assay that does not require mass-spectrometry equipment or expertise.

METHODS: Serum specimens from patients with known light chain myelomas and controls were subjected to ultrafiltration through a membrane with pore size of 50 kDa. The filtrate was concentrated and tested by immunofixation electrophoresis. The relative area under the monoclonal peak, compared to that of the total involved light chain composition, was estimated by densitometric scanning of immunofixation gels. The proportion of the area occupied by the monoclonal peak in representative densitometric scans was used to arrive at the total serum concentration of the monoclonal serum free light chains.

RESULTS: Using an ultracentrifugation and concentration process, monoclonal serum free light chains were detectable, along with polyclonal light chains, in all 10 patients with active light chain myelomas. Monoclonal light chains were identified in serum specimens that did not reveal monoclonal light chains by conventional immunofixation electrophoresis. The limit of detection by this method was 1.0 mg/L of monoclonal serum free light chains.

CONCLUSION: The method described here is simple enough to be implemented in academic medical center clinical laboratories and does not require special reagents, equipment, or expertise. Even though urine examination is the preferred method for the diagnosis of light chain plasma cell myelomas, measurement of the concentration of serum free light chains provides a convenient, albeit inadequate, way to monitor the course of disease. The method described here allows effective electrophoretic differentiation of monoclonal serum free light chain from polyclonal serum free light chains and provides a quantitation of the monoclonal serum free light chains in monitoring light chain monoclonal gammopathies.

Medienart:

E-Artikel

Erscheinungsjahr:

2020

Erschienen:

2020

Enthalten in:

Zur Gesamtaufnahme - volume:51

Enthalten in:

Laboratory medicine - 51(2020), 6 vom: 02. Nov., Seite 592-600

Sprache:

Englisch

Beteiligte Personen:

Singh, Gurmukh [VerfasserIn]
Bollag, Roni [VerfasserIn]

Links:

Volltext

Themen:

Antibodies, Monoclonal
Biomarkers
Immunofixation electrophoresis
Immunoglobulin Light Chains
Immunoglobulin kappa-Chains
Immunoglobulin lambda-Chains
Journal Article
Light chain myeloma
Monoclonal serum free light chains
Multiple myeloma
Plasma cell myeloma
Ultrafiltration

Anmerkungen:

Date Completed 21.07.2021

Date Revised 21.07.2021

published: Print

Citation Status MEDLINE

doi:

10.1093/labmed/lmaa012

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM308701305