Interference of M-protein on Thrombin Time Test: A Case Report

Abstract Objective A case of interference of monoclonal protein (M-protein) on thrombin time (TT) test in a 39-year-old Caucasian male patient is presented. Methods Coagulation screening tests were performed where altered results only for TT result (>150 seconds) and activated partial thromboplastin time (aPTT) result (36 seconds) were measured. Further specific coagulation testing included measurement of individual coagulation factors FII, FV, FVII, FVIII, FIX, FX, FXI, and FXII. Diagnostic steps in detection and identification of monoclonal protein included serum protein electrophoresis and immunofixation (both serum and urine specimen). Results Monoclonal protein immunoglobulin G kappa detection and identification in serum and urine clarified the situation. Conclusion Unexpectedly altered results of screening coagulation tests without any appropriate clinical signs and symptoms in a patient without any anticoagulant therapy needs to be critically considered in the context of extended next diagnostic steps in order to clarify the cause of pathological test results.