Dr Alfonso Iorio is a professor in the Division of Hematology and Thromboembolism, Division of General Internal Medicine, and Department of Health Research Methods, Evidence, and Impact at McMaster University.
What tests do you perform in a patient with a suspected bleeding disorder who has normal coagulation screening test results (platelet count, prothrombin time, partial thromboplastin time, thrombin time, fibrinogen)?
Alfonso Iorio, MD, PhD: It is a common situation and there are 2 guiding principles. One is that you need a severe deficiency of a clotting factor to see abnormality in the screening test. Even with a normal screening test you can still have common clotting disorders and you go by prevalence. First, you test for von Willebrand factor disease, so von Willebrand factor antigen and von Willebrand factor ristocetin cofactor activity, and then you test for factor VII, factor VIII, factor IX.
The second important concept is that there is one rare bleeding disorder that does not affect screening tests: factor XIII deficiency. It is a rare disorder, about 1 in 1,000,000 in the population. But it may be very severe and there is an easy treatment. A single administration of fresh frozen plasma can save a life. We always need to remind ourselves to measure factor XIII when the screening test results are normal.