Previous articles in this series have dealt with the prothrombin time (PT) and the coagulation time (CT).1,2 For many years these were the only tests available for the detection of clotting disorders. With the development of the thromboplastin generation test (TGT) and the partial thromboplastin time (PTT3,4), clinically important clotting defects which previously went undetected now can be identified. The TGT and PTT are not substitutes for the PT; they are sensitive to different clotting factors. However, the use of the TGT and PTT has largely done away with the usefulness of the Lee-White test. Even when the CT is made more sensitive by the use of tubes coated with silicone, the test remains less sensitive to mild clotting disorders than the TGT or PTT (unpublished data). In addition, for the detection of clinically significant deficiencies of factor VIII (antihemophilic factor) or IX (plasma thromboplastin component), the PTT
Didisheim P. Tests of Blood Coagulation and Hemostasis: III. The Partial Thromboplastin Time. JAMA. 1967;199(3):201. doi:10.1001/jama.1967.03120030105019
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