Preanalytical Stability of Adrenocorticotropic Hormone Depends on Time to Centrifugation Rather than Temperature

Preanalytical factors can affect reliability of hormone assay results. Adrenocorticotropic hormone (ACTH) in blood is considered highly unstable because of proteolytic degradation (1)(2)(3)(4), so storage of blood samples on ice until analysis is recommended. In clinical practice, however, this procedure may present logistical problems because most samples for ACTH measurement must be shipped from the place of sample collection to the laboratory. Therefore, we studied the impact of time and temperature before plasma separation and analysis on the results of ACTH assays.At 8 am, we obtained 2 blood samples from each of 19 healthy volunteers and 2 patients with pathologically high ACTH values (1 with Addison disease and 1 with congenital adrenal hyperplasia). Volunteers and patients gave written informed consent, and the ethics committee for our institution approved the study. ACTH concentrations were 5–774 ng/L. As recommended by the manufacturer (Monovette, Sarstedt), collection tubes contained 1.2–2 g of potassium EDTA/L, with a maximum 1% dilution effect of liquid EDTA.For each …