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

A Complete Blood Count (CBC) requires whole blood for analysis. This is because a CBC evaluates multiple components of blood, including red blood cells, white blood cells, and platelets. Whole blood contains all these elements in their natural state, allowing for accurate assessment of their quantities and conditions.

Serum and plasma might seem relevant, but they are derived from whole blood after certain processes. Serum is obtained after blood has clotted and the clot has been removed, while plasma is obtained from anticoagulated blood. These components would not provide a complete picture of the cellular components critical to a CBC because they lack certain cellular fractions.

A blood smear is a technique used to visually assess blood cells under a microscope, but it is not a type of sample itself for CBC purposes. It requires whole blood to prepare the smear, confirming that whole blood is essential for an accurate CBC. Using whole blood ensures that all key cellular characteristics can be evaluated, making it the appropriate choice for this type of analysis.