Which statement is true regarding WBC differential calculation?

• A. The average is obtained by multiplying the sums by ten.
• B. The average is obtained by dividing the sum of counts by ten.
• C. Absolute WBC numbers are not related to total WBC count.
• D. You do not need to know the total WBC count to calculate absolute numbers.

Answer: (B)

In a manual WBC differential, you gather data by counting cells across several fields and then turn those counts into an average to get a stable estimate. When you examine ten fields, you sum the number of cells of each type across all ten fields and then divide by the number of fields (ten). This gives the average number of that cell type per field, which helps standardize the differential since you’re basing your conclusion on more than a single microscopic view.

So dividing the sum of counts by ten is the step that yields the per-field average, making it the true statement. The other options aren’t correct because: multiplying the sums by ten would inflate the result and isn’t how you compute an average; absolute WBC numbers do relate to the total WBC count (they’re derived from the total count and the differential percentages); and you do need the total WBC count to calculate actual absolute numbers for each cell type.