Which test measures the number of platelets in blood?

• A. PKU test
• B. Platelet count
• C. PSA
• D. Prothrombin Time

Answer: (B)

Platelet count directly quantifies the number of platelets in the blood, reflecting a person’s primary hemostasis capacity. Platelets are small cell fragments essential for forming the initial plug to stop bleeding, so counting them per microliter shows whether there are enough to function properly and helps detect conditions like low platelets or high platelet numbers.

The other tests measure different things: the PKU test screens newborns for phenylketonuria, a metabolic disorder; PSA checks the level of prostate-specific antigen for prostate health; and Prothrombin Time assesses how long blood takes to clot, reflecting the activity of clotting factors rather than the actual platelet count.