Which type of blood sample is needed for a Complete Blood Count (CBC)?

A Complete Blood Count (CBC) requires a whole blood sample because the test evaluates various components of the blood, including red blood cells, white blood cells, and platelets, all of which are present in whole blood. By using whole blood, the laboratory is able to analyze these cellular components accurately, achieving insights into a patient's overall health.

Whole blood is typically collected using an anticoagulant-coated tube that prevents the blood from clotting, ensuring that all cells remain suspended in the liquid portion of the specimen. This allows for effective counting and analysis of blood cells.

In contrast, serum is obtained after blood has clotted and does not contain cellular elements, making it unsuitable for the CBC, which specifically measures these cellular components. Plasma, while it does contain many of the cells, is generally used for tests that measure specific components dissolved in the liquid, such as electrolytes or hormone levels. Platelet-rich plasma has a concentration of platelets higher than that typically found in whole blood but lacks the complete representation of other cells needed for a CBC.

Thus, a whole blood sample is essential for a Comprehensive evaluation of blood cells in a CBC.