is about has_specified_output blood coagulation scalar measurement datum assay prothrombin time assay Alan Ruttenberg An assay that measures the prothrombin ratio, which is the prothrombin time for a patient, divided by the result for control plasma. Most commonly the test is preformed using blood plasma. Blood is drawn into a test tube containing liquid citrate, which acts as an anticoagulant. An excess of calcium is added to enable the blood to clot again.Tissue factor (also known as factor III or thromboplastin) is added, and the time the sample takes to clot is measured optically as the prothrombin time, which is compared to a control sample. PMID:19696660#The prothrombin time (PT) was quantitatively determined using RecombiPlasTin (Instrumentation Laboratory Company, Lexington, Massachusetts, USA). url:http://en.wikipedia.org/wiki/Prothrombin_time@2009/10/06 prothrombin time assay metadata complete