Evaluation of plasma ACTH stability using the Roche Elecsys immunoassay.

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 h delay in separation of plasma from cells. Average percent differences in plasma ACTH concentration from time 0 was <10% up to 12 h at ambient temperature. Refrigeration of plasma did not preserve ACTH stability at 12 h and longer storage resulted in significant ACTH degradation at both ambient and refrigerated temperatures.
Conclusions: As supported by these data, previously recommended strict specimen collection and processing requirements are not necessary for measuring ACTH with the Roche Elecsys immunoassay.
(Copyright © 2020 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)