What type of blood sample is required for an arterial blood gas test?

An arterial blood gas (ABG) test specifically requires an arterial blood sample because it measures the levels of oxygen, carbon dioxide, and pH, which are critical indicators of respiratory function and metabolic state. Arterial blood differs from venous blood because it is oxygen-rich and is under higher pressure as it is directly transported from the heart to the tissues. When assessing how well oxygen is being delivered to the body and how effectively carbon dioxide is being removed, obtaining an arterial sample provides the most accurate representation of these parameters, as well as the body's acid-base balance.

Venous blood, on the other hand, would not give an accurate reflection of the oxygen content and other critical factors, making it inappropriate for ABG testing. Capillary blood samples can sometimes be used for preliminary assessments in children or in specific scenarios but generally do not provide the accuracy required for a formal ABG test. Serum samples, which are obtained after blood has clotted and the clot has been removed, are not suitable for ABG analysis either, as they lack the cellular components and gases of whole blood necessary for this specific testing.