Bethesda inhibitor assay is used to measure what?

• A. It measures the amount of antibody against factors in Hemophilia A and B
• B. It measures platelet function
• C. It measures bilirubin
• D. It measures RBC enzymes

Answer: (A)

The Bethesda inhibitor assay measures neutralizing antibodies against clotting factors, most commonly factor VIII in hemophilia A and factor IX in hemophilia B. It quantifies the inhibitor titer in Bethesda units per milliliter, telling you how strong the patient’s antibodies are at blocking the replacement factor. This matters clinically because the presence and level of inhibitors determine how effectively factor replacement will work and guide treatment decisions, such as using bypassing agents or immune tolerance strategies. It does not assess platelet function, bilirubin, or red blood cell enzymes, which is why the other options aren’t accurate.