A prolonged PTT is corrected when mixed with normal plasma and tested immediately and after a 2-hour incubation.Which test (or tests)should be performed next?

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This pattern suggests a factor deficiency,and factor VIII and IX assays should be performed.The Bethesda titer is performed when a specific factor inhibitor is present;no evidence exists for this because the PTT on the incubated 1:1 mix did not prolong.High-phospholipid PTT testing is done to confirm the lupus anticoagulant;this is not present because the immediate 1:1 mix on this sample corrected.No reason exists to perform an anti-Xa assay,often used to monitor LMWH.

A Prolonged PTT Is Corrected When Mixed with Normal Plasma