A chromogenic assay of prothrombin compared with coagulation tests during anticoagulant therapy and liver disease

A standardized chromogenic assay of prothrombin (factor II, FII) was compared with a conventional coagulation assay and global tests (Quick prothrombin time, Hepatoquick) in patients on oral anticoagulant therapy. Twenty patients with chronic liver disease were also investigated. Studies of precision showed a coefficient of variation ranging between 2.9 and 4.1% in both normal and anticoagulant samples. Accuracy and variability studies yielded satisfactory results. There was a highly significant positive correlation between chromogenic and coagulation assays, whereas correlation with global coagulation tests was much lower, particularly when normal plasmas were tested. In patients with liver disease, FII assay gave reduced values and appeared at least as sensitive as global coagulation tests in showing the synthetic defect occurring in liver disease. These findings suggest that the chromogenic assay can be employed in the clinical laboratory, even though prospective studies are warranted to establish its predictive value.