Final answer:
In a manual differential white blood cell count, 100 white blood cells are counted on a stained blood smear. This count helps determine the relative percentages of different leukocyte types under a microscope after staining with Wright-Giemsa stain.
Step-by-step explanation:
When performing a manual differential white blood cell count on a stained blood smear, typically 100 white blood cells are counted. This process is done after preparing a slide with a Wright-Giemsa stain, which helps in the identification of different white blood cell types under a light microscope. By using a systematic scanning pattern and a tally system, each type of leukocyte encountered is identified and recorded. Counting 100 cells allows the technologist to determine the relative number or percentage of each white blood cell type present in the smear. Observations can then be compared against normal ranges to evaluate whether the smear appears normal or abnormal.