Which description best defines a complete blood count (CBC)?

• A. It counts and characterizes blood cells using impedance or optical methods to give WBC, RBC, Hb, Hct, platelets, and indices
• B. It evaluates coagulation times
• C. It detects pathogens in blood
• D. It only measures red blood cell count

Answer: (A)

A complete blood count is an automated, broad assessment of the blood’s formed elements. Modern analyzers use electrical impedance or optical methods to count and size cells as they pass through the instrument. It provides the main components—white blood cells, red blood cells, hemoglobin concentration, and hematocrit—as well as platelets, plus red cell indices such as mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and red cell distribution width. These data together describe the quantity and character of blood cells, helping evaluate anemia, infection, and platelet-related issues. The other described tests don’t fit: coagulation times are measured separately, pathogens aren’t detected by a CBC, and a CBC includes more than just red blood cell count.