The partial thromboplastin time with kaolin. A simple screening test for first stage plasma clotting factor deficiencies.

Abstract

The partial thromboplastin time (PPT) test consists of recalcifying plasma in the presence of a lipid reagent that supplies optimal platelet thromboplastic factor-like activity. Thus, the test measures the overall adequacy of the intrinsic plasma-clotting factors. It has proven particularly valuable in the recognition of hemophilia and the hemophilioid states, i.e., deficiencies of antihemophilic globulin (AHG, Factor VIII), of plasma thromboplastin component (PTC, Factor IX), of plasma thromboplastin antecedent (PTA), and of Hageman factor (HF). Despite its simplicity, the PTT is not widely used in clinical laboratories. Instead, when faced with the task of screening patients for possible plasma thromboplastic factor deficiencies, most laboratories either rely upon insensitive or erratic technics, such as clotting times or prothrombin consumption tests, or resort to the complicated thromboplastin generation test. This neglect of the partial thromboplastin time technic has stemmed partly from the lack of a commercially available partial thromboplastin and partly from a failure to obtain short clotting times consistently with normal plasma in some laboratories. Waaler has demonstrated that long times with normal plasma may be caused by inadequate contact activation of the test plasma when