Improved Instrumentation for the Determination of Prothrombin Activity.

\\TIDESPREAD use of oral anticoagulant thei’apy has made prothrombin time one of the most frequently requested determinations in the clinical laboratory. In order to maintain clinical safety and the effectiveness of anticoagulants it is imperative that a pi’ocedui’e be employed which is maximally reliable almd reproducible, amid which permits as little variation jim individual technic as possible. The method of Owren (1) as modified origimmally by Ware and Stragiiell (2), and more recently by Ware et al. (3), has been employed in our laboratory for more than 10 years. The technic has been found to be technologically reliable aimd clinically effective in aiding physicians in the regulation of anticoagulant therapy (4). This paper presents a method for the semiautomatioii of the Ware et al. modification in which a diluting apparatus is incorporated to mix plasma and reagemmts and an end-point detector is employed. These changes have increased time work-output per technician ammd decreased training time, while maintaining the accuracy and reproducibility of the original nmanual technic.