Novel rhodamine tripeptide substrate for manual and automated colorimetric prothrombin time test

A chromogenic prothrombin time test is described using the tripeptide substrate, (Sar-Pro-Arg)2-Rhodamine 110. The method is both precise and sensitive to the factors of the extrinsic pathway. The accuracy of the method was demonstrated by comparison of patient sample values to standard clotting test results. The manual substrate test was adapted to two different automated chemistry analyzers.