Pre-analytical stability of adrenocorticotrophic hormone from healthy horses in whole blood, plasma and frozen plasma samples.

The stability of equine adrenocorticotrophic hormone (ACTH) in blood samples is not fully known. The study objectives were to determine ACTH stability (1) in whole blood and plasma over 72 h at either 4 or 21 °C, and (2) in plasma frozen at either -20 or -80 °C over 30 days. Nine horses were sampled and ACTH concentration were measured after storage as whole blood or plasma, at 4, 21, -20 and -80 °C for up to 30 days. The ACTH concentration was significantly reduced at 24 h but remained stable when plasma was frozen at -20 and -80 °C for 30 days. Beyond 24 h, samples stored at 21 °C showed a greater reduction in ACTH concentrations than those stored at 4 °C. Therefore, samples can be stored for 8 h without centrifugation, or frozen for 30 days without appreciable reductions in ACTH concentrations.