... abnormalities is shown in Table 59-4. Chapter 059. Bleeding and Thrombosis (Part 8) Screening Assays The most commonly used screening tests are the PT, aPTT, and platelet count. The PT assesses ... reagents to clotting factor deficiencies and to inhibitors such as heparin and lupus anticoagulants. Thus, aPTT results will vary from one laboratory to another, and the normal range in the laboratory ... overestimate the bleeding risk of a mildly elevated INR in this setting. The aPTT assesses the intrinsic and common coagulation pathways, factors XI, IX, VIII, X, V, II, fibrinogen, and also prekallikrein,...