A Case of Clinical Confusion Due to Erroneous M-protein Quantifications: To Splice or Skim?

Abstract

An M-protein identified on electrophoresis is conventionally quantified by integrating the M-spike from baseline (PD), invariably including some irrelevant/background proteins. The use of an alternative approach that skims the M-spike tangentially thereby excluding the background proteins (TS), however, has been scanty. We report herein a case in which PD overestimated the M-proteins inconsistently, leading to confusion over relapse in a multiple myeloma patient. At diagnosis, a 65-year old male had an IgG kappa M-spike of 44 g/L which decreased to 6 g/L (PD) following chemotherapy. Six weeks after autologous stem cell transplantation (ASCT), two M-spikes measuring respectively 10 and 5 g/L emerged. Together with decreases in hemoglobin and blood cell counts, a relapse was suspected. Bone marrow examinations, however, did not reveal any significant plasmacytosis or clonal restriction. Re-analyses by TS reduced the original M-protein estimations by 12% and 88% pre- and post-ASCT respectively, and corroborated the disease activity/status consistently.

• Authors: Pak Cheung Chan, Amir Karin, Signy Chow
• Journal: EJIFCC (EJIFCC) Vol. 33 Issue 4 Pg. 334-341 (Dec 2022) ISSN: 1650-3414 [Electronic] Italy
• PMID: 36605304 (Publication Type: Case Reports)
• Copyright: Copyright © 2022 International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). All rights reserved.