Effect of Serum Immunoglobulins on Routine Coagulation Tests: A Comparison of Coagulation Analyzers using Mechanical and Optical Clot Detection

We previously showed that the prothrombin time (PT), but not activated partial thromboplastin time (APTT), is correlated with serum immunoglobulin level in patients with plasma cell neoplasms. To determine if the observed effect of serum immunoglobulins on PT was reagent and/or method dependent, PT and APTT were measured in plasma samples obtained from patients referred to the Myeloma Institute using mechanical (STAR Evolution; Diagnostica Stago) and optical clot detection (ACL TOP 500 analyzer; Instrumentation Laboratory) and manufacturer provided reagents. A total of 97 patients were included in this study. Twelve patients had abnormal coagulation test results. An isolated prolonged PT was found in 8 patients and an isolated prolonged PTT was detected in 4 patients. The PT, but not APTT, was positively correlated with serum paraprotein level and this correlation was observed regardless of the reagents and instrumentation used to assess clot time.