How do you evaluate an isolated prolonged aPTT in patients?

This is a common problem.

First, if possible, find out if there has been a normal PTT in the past which usually eliminates inherited deficiencies.

Second, take a bleeding and clotting history including family history, presence of known liver disease, and any medications. Sometimes it is not recognized that DOACs cause this.

Then, depending on need, i.e surgery, etc. would do a mixing study which would distinguish an inhibitor versus deficiency. If it does not correct, suggest an inhibitor and do a lupus anticoagulant. If the patient is bleeding, would also send factor levels for 8.9.11.12.

If this does not distinguish rarely you need to check for deficiency of HMW -kininogen or patient with polycythemia. In the case of polycythemia, the exc...