Activated Partial Thromboplastin Time and Prothrombin Time Mixing Studies: Current State of the Art

Abstract

Mixing studies have long been in the clinical laboratory armamentarium for investigating unexpected, prolonged activated partial thromboplastin time (aPTT) or prothrombin time (PT). The purpose of the mixing study is to identify whether the aPTT/PT prolongation is secondary to a factor deficiency versus an inhibitor, which would present as a “corrected” and “noncorrected” mixing study, respectively. The differentiation between a factor deficiency and inhibitor may likely further direct clinical decisions, including additional diagnostic testing or factor replacement therapy. While aPTT/PT mixing studies are simple tests to perform, there is a lack of standardization for both the testing protocol and the interpretation of what is considered to be a corrected or noncorrected mixing study result. This review will describe the common indications for the mixing test, preanalytic variables that may affect mixing study performance, and describe several methods for interpreting the results of aPTT and PT mixing tests.

International Council for Standardization in Haematology Guidance for New Lot Verification of Coagulation Reagents, Calibrators, and Controls

“…-Acceptability would be an agreement with mixing study interpretation locally defined 30 as follows:…”

Simultaneous hemorrhage and venous thrombosis in a patient with systemic lupus erythematosus

“…The aPTT fully corrects during the mixing study in patients with hemophilia A and B and inherited defi ciencies of factor XI, factor XII, and contact factors. 7 Hemophilia C, or factor XI defi ciency, is an autosomal dominant or recessive trauma-associated bleeding disorder caused by factor XI defi ciency and is commonly seen in Ashkenazi and Iraqi Jewish populations. 8 Although factor XII defi ciency and other contact factors (highmolecular-weight kininogen and plasma prekallikrein) cause markedly prolonged aPTT, factor XII defi ciency does not cause any bleeding diathesis.…”

Carbonization of quercetin into nanogels: a leap in anticoagulant development

“…PT assays were employed to evaluate the extrinsic coagulation pathway by analyzing coagulation factors II, V, VII, X, and fibrinogen. 57 aPTT is primarily used to monitor the common pathway and factors XII, XI, IX, VIII, X, V, II, and fibrinogen in the intrinsic pathway. 57 While CNGs Qur270 and CNGs Qur290 (100 μg mL −1 ) slightly extended the aPTT time (73 and 121 s, respectively) compared to quercetin, CNGs Qur290 and CNGs Qur310 (100 μg mL −1 ) proved to be much more effective, with PT times of 1090 and >1200 s, respectively (Fig.…”