What part of the CBC is the most accurate procedure?

• A. Hematocrit
• B. Erythrocyte count
• C. Leukocyte count
• D. Hemoglobin determination

Answer: (A)

The most accurate part of a CBC is hematocrit because it directly measures the proportion of blood volume made up by red blood cells. By centrifuging a small sample in a capillary tube, you separate RBCs from plasma and then read the actual volume fraction of RBCs, which reflects the total RBC mass. This physical measurement is less dependent on counting individual cells or interpreting color changes, which can introduce errors in erythrocyte counts, leukocyte counts, or hemoglobin assays. Counting cells can be affected by clumping, smear quality, or instrument calibration, while hemoglobin concentration can be influenced by sample handling or interference in colorimetric readings. Thus, hematocrit provides a robust and rapid estimate of red cell mass, making it the most accurate procedure in a CBC.