Mixing studies correct indicates factor deficiency?

• A. Factor deficiency
• B. Presence of an inhibitor such as lupus anticoagulant
• C. Fibrinogen abnormality
• D. Vitamin K deficiency

Answer: (A)

Mixing studies distinguish between a true deficiency of coagulation factors and the presence of an inhibitor that interferes with clotting. When patient plasma is mixed with normal pooled plasma, if the prolonged clotting time returns to normal, it means the normal plasma supplied the missing factors and the issue was a deficiency. An inhibitor, such as lupus anticoagulant, would continue to block the reaction even after mixing, so the prolongation would persist. Therefore, a corrected mixing study points to a factor deficiency rather than an inhibitor.