A 37-year-old female patient has a PTT of 76 seconds (reference range, 25 to 37 seconds). Her plasma is mixed 1:1 with normal plasma. An immediate PTT performed on the mix is 74 seconds. Which of the following is the most likely diagnosis?

Question

Quizplus · Accepted Answer

A prolonged PTT with a mixing study that corrects the time suggests a factor deficiency, while a persistent prolonged PTT suggests the presence of an inhibitor or a lupus anticoagulant. The fact that the PTT did not correct after mixing, suggests the presence of a factor inhibitor or lupus anticoagulant. Since lupus anticoagulants are typically associated with thrombosis or recurrent pregnancy loss, and since the question stem does not mention any other clinical signs of lupus or thrombosis, an inhibitor is the most likely cause. Hemophilia A would present with a persistently prolonged PTT, but the mixing study would not result in a significant correction. Intrinsic factor deficiency is unrelated to the coagulation cascade.

A 37-Year-Old Female Patient Has a PTT of 76 Seconds