In a mixing study, failure to correct after mixing with normal plasma most strongly suggests which of the following?

In a mixing study, failure to correct after mixing with normal plasma most strongly suggests which of the following?

• A. Factor VII deficiency
• B. Presence of an inhibitor or anticoagulant effect
• C. Normal coagulation factors
• D. Platelet function defect

Answer: (B)

Mixing studies differentiate factor deficiency from an inhibitor. When patient plasma is mixed with normal plasma, a true factor deficiency is replenished by the normal plasma and the prolonged clotting time should correct. If the clotting time does not correct, it suggests an inhibitor or anticoagulant present in the patient’s plasma that continues to interfere with the coagulation process despite the added factors. This fits scenarios such as antibodies against a specific factor (factor inhibitors) or substances like lupus anticoagulant or residual anticoagulants in the plasma. Platelet function defects generally do not get corrected by mixing plasma, because the test relies on plasma factors rather than platelet performance, so a lack of correction most strongly points to an inhibitor or anticoagulant effect.

Mixing studies differentiate factor deficiency from an inhibitor. When patient plasma is mixed with normal plasma, a true factor deficiency is replenished by the normal plasma and the prolonged clotting time should correct. If the clotting time does not correct, it suggests an inhibitor or anticoagulant present in the patient’s plasma that continues to interfere with the coagulation process despite the added factors. This fits scenarios such as antibodies against a specific factor (factor inhibitors) or substances like lupus anticoagulant or residual anticoagulants in the plasma. Platelet function defects generally do not get corrected by mixing plasma, because the test relies on plasma factors rather than platelet performance, so a lack of correction most strongly points to an inhibitor or anticoagulant effect.