Utility and Interpretation of Coagulation Mixing Studies

Abstract

Coagulation testing is essential for the diagnosis and management of a variety of hemophilia, thrombophilia, and complicated coagulopathies. This is often used prior to surgery, or as a follow-up investigation for patients being scrutinized for bleeding diathesis, or to monitor the anticoagulant therapy. When the results are abnormal, a mixing study is often the initial reflexive test that can provide valuable information to conclude the assessment, or help guide further investigations. If the mixing “corrects” the test results, a factor deficiency would be suspected. Otherwise, the presence of an inhibitor would be more likely. However, defining “correction” remains difficult and controversial. There are several available methods to determine whether a result is corrected. Each method has its own advantages and limitations. It is noteworthy that although a complete correction can be interpreted as factor deficiency, a partial or incomplete correction does not rule out the coexistence of factor deficiency and the presence of a coagulation inhibitor. Hence, caution should be taken in interpreting mixing study results for patients who are taking direct-acting oral anticoagulants. Ideally, mixing study results are interpreted in correlation with the patient’s clinical history, including bleeding or thrombosis history, and the use of anticoagulants.