When an Analytical Interference Is a Useful Diagnostic Tool: Finding Monoclonal Gammopathies in Routine Analysis

The daily productivity of a clinical laboratory depends on the large number of interferences that affect analytical accuracy. Obviously, they have always been considered as a very important aspect to keep accuracy under control. Nevertheless, we wondered if this aspect would be beneficial. In this article, we propose a method for finding monoclonal gammopathies that are based on the fact that the presence of paraprotein in the sample may interfere with routine laboratory assays, specifically, with the quantification of uric acid and conjugated bilirubin.

Over a 5-month period, we evaluated 18,278 sera samples of patients from primary care. None of them were suspected of having plasma cell dyscrasias (not observed hypercalcemia, renal failure, anemia, and/or lytic bone lesions). Although biochemical findings suggested paraprotein interference, we carried out serum capillary electrophoresis (CE) and quantification of immunoglobulins and serum-free light chains (SFLCs). We also confirmed the results obtained by performing the corresponding immunofixation electrophoresis (IFE). Flow cytometry analyses were conducted for immunophenotypic characterization of plasma cells from these patients.

The proposed detection method allowed us to identify eight patients with previously undiagnosed monoclonal gammopathy.

The results show that it is possible to use analytical interference for diagnostic purposes, and most importantly, almost all cases were identified at an early stage of the disease, when associated clinical manifestations were not yet observed.