Evaluation of an automated prothrombin assay using a chromogenic substrate.

The performance of a commercially available assay for the determination of prothrombin by a chromogenic substrate method has been evaluated for use on an automated clinical analyser. The method was rapid and simple; accuracy, precision and sensitivity were satisfactory, while carry-over was negligible. Determinations were performed on 170 plasma samples from patients on long-term oral anticoagulant therapy, using the automated amidolytic method; comparison of the prothrombin levels with results obtained by the prothrombin time and Thrombotest methods provided highly significant correlations.