The unwarranted use of replicate analysis in routine coagulation studies

The need to assure the validity of semiautomated coagulation procedures by performing replicate determinations is assessed. Prothrombin times (PT) and activated partial thromboplastin times (aPTT) were run as duplicate assays using two different photo-optical detection systems. Sixty specimens with a broad range of PT and aPTT results were studied as aliquots of 80, 100, and 140 μL of plasma. A total of 1,440 studies were performed. No statistically significant differences were found among the data for complementary groups of assays. It is concluded that replicate analyses do not enhance the precision nor the accuracy of these coagulation studies. These factors are more controlled adequately by quality assurance procedures, including frequent calibration checks, the use of internal standards, and multilevel commercial controls.