An illustrated review of bleeding assessment tools and common coagulation tests

Abstract

Recognizing the complexity of coagulation tests and currently used anticoagulants, we developed this illustrated review on bleeding assessment tools and common coagulation screening tests. Quantitative bleeding assessment tools (BATs) are available to standardize the bleeding history and improve the pretest probability prior to coagulation testing. We describe use of BATs and the principles, indications, and limitations of the prothrombin time (PT)/International Normalized Ratio, activated partial thromboplastin time (APTT), and 50:50 mix. Use of these tests to identify coagulation factor deficiencies, specific and nonspecific inhibitors, coagulopathy of liver disease, disseminated intravascular coagulation, and commonly used anticoagulant medications are reviewed. Current literature suggests that unnecessary coagulation testing is rampant. The PT and APTT have astoundingly low sensitivity (1.0%‐2.1%) for detection of clinically significant bleeding disorders. Thus, current guidelines recommend against the use of screening PT and APTT in preoperative patients undergoing noncardiac/vascular surgery.

Platelet Phenotyping and Function Testing in Thrombocytopenia

“…The use of a standardized bleeding assessment tool (BAT) is recommended to calculate a bleeding score for the accurate evaluation of the bleeding tendency. In addition to the bleeding score of the World Health Organization (WHO), several BATs have been established, especially for type 1 VWD [ 24 ]. More recently, the SSC “Platelet Physiology” of the ISTH performed a validation study to test the diagnostic utility of the type 1 VWD ISTH-BAT for inherited platelet function and number disorders in a large cohort with more than of 1000 patients across 17 countries worldwide [ 25 ].…”

New onset of acute heavy menstrual bleeding in a 34-year-old woman

“…An isolated, prolonged aPTT in a bleeding patient with no anticoagulation exposure should raise suspicion for defects of the intrinsic pathway of coagulation (factors VIII, IX, XI), which can be caused by either a deficiency of a coagulation factor or an inhibitor that interferes with the factors' activity. 2,3 Although factor XII is also part of the intrinsic pathway, deficiencies lead to in vitro prolongation of aPTT without associated bleeding tendencies. 2,4 Abnormalities in von Willeband factor levels do not prolong the aPTT, unless there is a concomitant factor VIII deficiency.…”

“…Mixing, or 50:50, studies, in which the patient's plasma is mixed with normal plasma at 1:1 ratio, 2,3 are performed in most laboratories to differentiate between factor deficiencies and the presence of inhibitors (Figure 1). 4 Clinicians need to request this test, as it is not automatically per-formed by laboratories.…”

“…The further prolongation of aPTT after incubation at 37°C Figure 1: Interpretation of mixing studies and suggested follow-up investigations. [1][2][3] Plasma from the patient with prolonged activated partial thromboplastin time (aPTT) is mixed with normal plasma in a 1:1 ratio. The aPTT test is performed immediately after mixture with plasma and after incubation for 1-2 hours at 37°C.…”

“…(i.e., showing time and temperature dependence) is typically seen only in patients with an acquired factor VIII inhibitor. 2,3 An acquired inhibitor to factor VIII, or acquired hemophilia A, is the most common acquired specific coagulation factor inhibitor. 4 A lupus anticoagulant may prolong the aPTT, which would also result in a lack of correction in aPTT during the mixing study.…”