The presence of a factor deficiency in the extrinsic and/or common pathway can be detected by performing a Prothrombin Time (PT) on a mixture of patient plasma and normal pool without incubation. A factor deficiency is indicated if the normal plasma corrects the elevated PT of the patient sample.
Send whole blood sample(s) at room temperature as soon as possible.
If specimens cannot be shipped immediately, centrifuge and separate plasma within 1 hour of collection, send frozen plasma on dry ice
PT mixing studies are not performed:
- if the PT falls within the normal PT Reference Interval. See Reporting.
- if the patient is on heparin or oral anticoagulant therapy. See Reporting.