What type of blood specimen is typically used for a complete blood count (CBC)?

A complete blood count (CBC) is a common blood test that evaluates several components of blood, including red blood cells, white blood cells, hemoglobin, hematocrit, and platelets. For this test, it is essential to use an anticoagulant that prevents the blood from clotting while preserving the cellular components for accurate analysis.

The lavender-top tube is specifically designed for hematology tests, including the CBC, as it contains EDTA (ethylenediaminetetraacetic acid), a potent anticoagulant. EDTA works by binding calcium ions in the blood, which are essential for the clotting process, thus keeping the blood in a liquid state and allowing the cells to be counted and analyzed effectively.

In contrast, other types of tubes, such as the blue-top or red-top tubes, do not contain this specific anticoagulant required for a CBC. The blue-top tube typically contains sodium citrate and is mainly used for coagulation tests. The red-top tube lacks an anticoagulant altogether and is used for serum tests where blood is allowed to clot before the serum is separated. The green-top tube contains heparin, which is sometimes used for different types of tests but not for a standard CBC, as it can