LAUSR

BACKGROUND Adrenocorticotropic hormone (ACTH) has been reported to be labile in blood due to proteolytic degradation and stringent procedures are followed to prevent in vitro degradation after sample collection. OBJECTIVE The purpose of this study was to examine the effect of time and temperature before and after separation of plasma from cells in the quantitation of plasma ACTH. METHODS Our current protocol includes sample collection in a pre-chilled tube, transport on ice and immediate centrifugation at 4°C. These reference conditions were compared against sample processing in tubes and centrifuge set at room-temperature; using delayed centrifugation at 4°C. ACTH stability was evaluated at ambient and refrigerated temperatures after collection and plasma separation using the reference protocol. Plasma samples were analyzed using the Roche Elecsys ACTH immunoassay. RESULTS Quantification of ACTH was not impacted by the use of non-chilled tubes and centrifuge and up to a 4 hour delay in separation of plasma from cells. Average percent differences in plasma ACTH concentration from time 0 was <10% up to 12 hours at ambient. Refrigeration of plasma did not preserve ACTH stability at 12 hours and longer storage resulted in significant ACTH degradation at both ambient and refrigerated storage. CONCLUSIONS As supported by these data, previously recommended strict specimen collection and processing requirements is not necessary for measuring ACTH with the Roche Elecsys immunoassay.