Frequently Asked Questions (FAQs)
APTT is a screening for Hemophilia A and B and other possible coagulopathies (except factors VII and XIII). PTT is not affected by single clotting factor defects above 40% of normal. It is also used for detection of clotting inhibitors. This is best performed by mixing studies once an otherwise unexplained prolonged PTT is found. The results should be clinically correlated.