Final answer:
A differential white blood cell count is used to determine the percentage of different types of white blood cells, helping to detect various health conditions, which confirms the statement is true.
Step-by-step explanation:
A differential white blood cell count is indeed used to determine the percentage of the five types of white blood cells in a sample, which includes granulocytes (neutrophils, eosinophils, and basophils) and agranulocytes (lymphocytes and monocytes). This count provides critical information regarding a patient's immune response and helps to detect conditions such as infections, inflammation, blood disorders, and the effects of poisoning, affirming the statement is A. True.
Technicians perform this test by creating a blood smear and using the Wright-Giemsa stain to highlight the different cell types for proper identification. By analyzing the smear and tallying up to 100 cells, the percentages of each cell type can be established. Comparing these values to established norms can help indicate the health status of a patient by revealing increased or decreased levels which might be associated with specific disease conditions.
For instance, an increase in neutrophils often indicates a bacterial infection, whereas an increase in lymphocytes may suggest a viral infection. Variations from the normal range of white blood cell counts provide physicians with clues about a patient's overall health and potential immune system challenges.