I learned about an interesting case at the University of Alabama at Birmingham(UAB) Hospital special coagulation lab today from specialty techs Patti Tichenor andLaura Taylor. A specimen arrived with an order for lupus anticoagulant profile and anti-cardiolipin antibody. The PTT was prolonged and corrected on initial mix.
The UAB protocol recommends a two-hour incubation and repeat mixing study on the incubated sample to detect a specific inhibitor, which usually turns out to be an anti-factor VIII antibody. Whether the result of the incubated mixing study is corrected, indicating a coagulation factor deficiency, or uncorrected, indicating a possible inhibitor, Patti and Laura typically go on to run a factor VIII assay during the incubation, reasoning they will want to do so in either event. It turns out the factor VIII activity was 38%, so they next ordered a von Willebrand factor antigen assay, which turns out to be 35%. The ristocetin cofactor results will follow, but a call to the ordering ophthalmologist reveals the patient was experiencing a retinal hemorrhage. Their appropriate and speedy application of the mixing study protocol provided an unexpected diagnosis and led to an appropriate treatment course.