What part of the CBC cannot be done manually with adequate accuracy?

What part of the CBC cannot be done manually with adequate accuracy?

• A. Erythrocyte count
• B. Leukocyte count
• C. Packed cell volume
• D. WBC differential

Answer: (A)

Counting red blood cells by hand is not reliable enough for accurate CBC results because their numbers are extremely large (millions per microliter) and small errors multiply into big relative mistakes; fatigue and sampling variation make manual RBC counts inconsistent, which is why automated counters are standard. In contrast, packed cell volume can be obtained by a simple centrifugation of a capillary tube and reading the hematocrit, a direct and reproducible measurement you can do manually with good precision. A manual WBC differential is performed by examining a stained smear under a microscope and, while time-consuming, can yield accurate proportions of each white cell type when done carefully. Leukocyte counts can also be estimated manually with a hemocytometer, but the RBC count remains the least amenable to manual, accurate determination.

Counting red blood cells by hand is not reliable enough for accurate CBC results because their numbers are extremely large (millions per microliter) and small errors multiply into big relative mistakes; fatigue and sampling variation make manual RBC counts inconsistent, which is why automated counters are standard. In contrast, packed cell volume can be obtained by a simple centrifugation of a capillary tube and reading the hematocrit, a direct and reproducible measurement you can do manually with good precision. A manual WBC differential is performed by examining a stained smear under a microscope and, while time-consuming, can yield accurate proportions of each white cell type when done carefully. Leukocyte counts can also be estimated manually with a hemocytometer, but the RBC count remains the least amenable to manual, accurate determination.