A comparative study of three methods measuring prothrombin time.

A comparative study of the Fibrometer, Seratek, and manual technics measuring prothrombin time is described.Three technicians, 3 thromboplastin preparations, and 10 blood specimens with 10 replications were utilized in a 3 X 3 X 10 factorial design. It was found that the reproducibility of each method was subject to an interaction between technician, method, and reagent. In the hands of experienced technicians, the Seratek method was more frequently reproducible than the other two methods. This does not rule out the possibility of the Fibrometer being the method of choice with any particular technician or when lessexperienced technicians are performing prothrombin time measurements in rotation. The Fibrometer was found to produce the shortest prothrombintime. The importance of consideringinteraction in comparative or quality control studies consisting of several variables is emphasized.