Authors
Sheng Wang, Xiaoyong Duan, Yulin Zou, Jianxiong Gui
Published in
Biochemia medica. Volume 36. Issue 3. Pages 030901. Oct 15, 2026. Epub Aug 10, 2026.
Abstract
Accurate measurement of serum electrolytes and calcium is essential for clinical management; however, monoclonal immunoglobulins, particularly IgM paraproteins, may cause misleading analytical interference. We report the case of an 85-year-old man admitted for low back pain whose serum sample showed marked inter-platform discordance in sodium and total calcium results. The Hitachi platform reported a "hypercalcemic crisis" (total calcium 4.95 mmol/L) and severe hyponatremia (125 mmol/L), whereas the Beckman Coulter AU platform showed only mildly elevated total calcium (2.89 mmol/L) and milder hyponatremia (133 mmol/L). This corresponded to a 71.3% difference in total calcium, despite both platforms using the Arsenazo III method. Direct ion-selective electrode measurements excluded true hyponatremia and hypercalcemia. Dilution studies, polyethylene glycol precipitation, reaction-curve inspection, and simulation experiments confirmed that IgM-related precipitation and optical scattering were the underlying mechanisms. Specifically, platform-specific mixing dynamics determined the magnitude of interference. Recognition of biochemical-clinical discordance and targeted method comparison prompted hematological evaluation and led to a diagnosis of Waldenström macroglobulinemia. This case highlights that unexplained analytical discrepancies may delay recognition of underlying disease if analytical interference is not appropriately investigated.
PMID:
42621974
Bibliographic data and abstract were imported from PubMed on 20 Aug 2026.
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