Coagulation screening test interpretation - mixing studies (factor deficiency vs inhibitor)
Core concept
- Prolonged PT/APTT of unclear cause is worked up with a mixing study: patient plasma + normal pooled plasma (1:1), retest the clotting time
- Corrects to normal -> original prolongation was due to a factor deficiency (normal plasma supplies the missing factor)
- Fails to correct (remains prolonged) -> an inhibitor is present (antibody or non-specific inhibitor consuming/blocking factor activity in both patient and normal plasma)
3 more sections, plus exam facts
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