Summary
Background. In recent years, monoclonal antibody therapy has become increasingly important in the treatment of multiple myeloma in Lithuania. Even it is known that low levels of these medicines can interfere electrophoresis assays and this problem is widely discussed, laboratories do not have any recommendations and often misinterpretation or inability to measure therapeutic responses happens. The aim of this article is to demonstrate the migration pattern of serum samples from patients treated with daratumumab and isatuximab in SPE and immunofixation, to describe a simple and effective method to remove daratumumab from patients' serum and to propose the use of reflex tests regarding this problem.
Methods. Data from 2 patients were retrospectively analysed. Capillary electrophoresis, immunofixation and Hydrasys 2/4 daratumumab procedures were performed.
Results. In all cases, the interference of monoclonal antibodies was established and visualised. Migration pattern was determined: isatuximab migrates to the fast gamma region in SPE, but to the mid gamma region in immunofixation, while daratumumab migrates to the slow gamma region in both assays.
Conclusion. This report highlights the importance of the ability to recognize possible interference of monoclonal antibodies by the visual electrophoresis images, which is crucial for the clinical outcome measures. It suggests including a reflex testing as a mandatory in the multiple myeloma patients who are treated with mAbs testing guidelines. Reflex testing should be performed on all patients for whom a new IgG kappa monoclonal protein is observed as well as for patients whose M-protein shares the same SPE migration as mAb.
