Is the stability of ACTH in whole blood a genuine concern during the preanalytical phase? A systematic review

Adrenocorticotropic hormone (ACTH) has historically been considered an unstable hormone after venous sampling, necessitating stringent conditions for the transport of blood samples to the laboratory to ensure accurate measurement. However, recent investigations suggest that ACTH may be more stable than previously assumed, raising the possibility of more flexible handling conditions. This prompted us to conduct a systematic review using the MEDLINE database to ascertain the stability of ACTH in blood samples. We included 9 studies in our final analysis from 405 reports. Our findings reveal that all studies reported a mean percentage difference (PD%) in ACTH concentrations relative to baseline below the 10% threshold when uncentrifuged tubes were stored under refrigerated conditions for 2, 4, 6, and 8 hours. In contrast, the mean PD% exceed the 10% threshold in 5 out of 7 studies investigating a storage duration of 24 hours under refrigerated conditions. Nearly all studies reported a mean PD% in ACTH concentrations relative to baseline below 10% when uncentrifuged tubes were stored at room temperature for 2, 4, and 6 hours. However, for storage durations of 8, 12, and 24 hours at room temperature, most studies observed a mean PD% exceeding 10%. In summary, our findings suggest that ACTH remains stable in uncentrifuged tubes containing EDTA for 6 h at room temperature and at least 8 h under refrigerated conditions. Our findings can assist clinical laboratories in reviewing their acceptance criteria for sample transport regarding time and temperature.