ACTH sampling: which tube is recommended?

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ACTH is a very labile peptide that rapidly degrades after blood is drawn, so preserving it requires immediate cooling and a suitable anticoagulant. Using a prechilled EDTA tube provides two benefits: the cooling slows enzymatic/proteolytic degradation, and EDTA acts as an anticoagulant without introducing substances that can interfere with many ACTH immunoassays. A prewarmed tube would promote degradation, and heparin (especially if not kept cold) can interfere with the assay or offer less stabilization. Therefore, the best choice is a prechilled EDTA tube to maintain ACTH integrity for accurate measurement.