During manual hematocrit testing, which factor can falsely increase the result?

• A. Trapped plasma from low RPM
• B. Hemolysis
• C. Increased EDTA
• D. Prolonged refrigeration

Answer: (A)

The key idea is that manual hematocrit accuracy depends on proper separation of plasma from red cells by centrifugation. If the centrifugation is done at too low a speed, the red cell column doesn’t pack tightly and plasma can become trapped within the cell layer. That trapped plasma makes the apparent height of the packed red cells larger, so the ratio of packed cells to total height is read as a higher value than the true hematocrit. The other factors listed don’t produce this specific readout artifact under standard procedures.