For catecholamine testing, which specimen type is described?

• A. Pre-chilled EDTA plasma
• B. Serum
• C. Whole blood in heparin
• D. Urine only

Answer: (A)

Catecholamines are highly labile and can change value quickly after collection due to ongoing metabolism and release from cells. To preserve their true circulating levels, the specimen must be handled on ice and processed rapidly. Using an EDTA tube prevents clotting, so platelets don’t release catecholamines during clotting (a common source of artificial elevation in serum). Chilling the sample slows enzymatic degradation and oxidation of catecholamines, helping maintain their actual in vivo concentration. Therefore, pre-chilled EDTA plasma provides the most accurate measurement for catecholamines compared with serum (which involves clotting and platelet release), whole blood in heparin (less stability and potential interference), or urine (measures excretion over time, not plasma levels).