Which statement about calculating absolute WBC numbers from differential is correct?

• A. Cells types are expressed in fractions.
• B. In order to find the absolute number you multiply the % cell seen by the WBC count.
• C. Example (30%) 0.3 x 10,000 = 3,000.
• D. Absolute numbers are the same as percentages.

Answer: (B)

To get an absolute WBC count from a differential, you apply the portion of cells represented by that type to the total WBC count. In practice, convert the percentage to a decimal and multiply by the total WBC count. For example, if the total WBC count is 10,000 per microliter and 30% are of the type in question, you calculate 0.30 × 10,000 = 3,000 cells per microliter. This gives the actual number of cells, not the share. Percentages describe the proportion, while the absolute count tells you how many cells there are. The method described aligns with the calculation shown in the example, which is equivalent to multiplying the percentage (as a decimal) by the total WBC count. Absolute numbers are not the same as percentages, since they are counts rather than portions of 100.