Which test is used as a presumptive indicator of blood based on hemoglobin's peroxidase-like activity?

• A. Luminol.
• B. Acid phosphate test.
• C. Kastle-Meyer test.
• D. Precipitin test.

Answer: (C)

Presumptive blood tests often rely on hemoglobin acting like a peroxidase enzyme to drive redox reactions that produce a visible change. In the Kastle-Meyer test, a sample is treated with hydrogen peroxide and phenolphthalein. If blood is present, the hemoglobin’s peroxidase‑like activity speeds the oxidation of phenolphthalein, turning it pink within seconds. This visible color change provides a rapid, straightforward indicator that blood may be present on a surface. Luminol also detects blood via a peroxidase‑driven reaction, but it produces light rather than a stable color, and it’s used differently to reveal trace or hidden blood. The acid phosphate test targets semen by detecting acid phosphatase, not blood, and the precipitin test identifies species origin, not a presumptive test for blood. So the Kastle-Meyer test is the best fit for a presumptive indicator of blood based on hemoglobin’s peroxidase-like activity.