Diagnosis of patients with IgM monoclonal gammopathy due to analytical interference

Blood hyperviscosity is a condition associated, in most cases, with Waldenström's macroglobulinemia (WM) and other plasma cell dyscrasias, primarily due to the pentameric structure of immunoglobulin (Ig) M. Analytical interference in the determination of alanine aminotransferase with the Abbott Alinity c assay has recently been documented, related to increased blood viscosity as a result of a monoclonal component. The detection of this interference indicates a significant and isolated increase in the concentration of a single immunoglobulin, leading to the diagnosis of a previously unknown monoclonal gammopathy.

Thanks to the described interference and the expansion of analytical testing by the clinical laboratory, 15 patients with a previously unknown IgM monoclonal component were identified over 7 months. IgM levels ranged from 8.37 g/L, with a monoclonal component of 2.4 g/L, to 82.43 g/L, with a monoclonal component of 40.9 g/L. Ten patients were diagnosed with IgM monoclonal gammopathy of undetermined significance, one with asymptomatic biclonal gammopathy, and one with WM who presented with hyperviscosity syndrome, requiring plasmapheresis and treatment with rituximab-bendamustine.

These cases highlight the importance of investigating laboratory test interferences, as they may be related to subclinical pathologies, such as monoclonal gammopathies. Detecting this interference and expanding laboratory testing can detect the pathology even before the appearance of related symptoms. This early identification allows for patient referral to the Hematology Department for appropriate follow-up, improving the prevention of complications and helping to make more timely therapeutic decisions.