Time but not storage of equine plasma in silicate-coated tubes affects adrenocorticotropic hormone stability
Year: 2025
Type: article
Abstract: Objective: Pituitary pars intermedia dysfunction (PPID) is diagnosed by measuring the ACTH concentrations. Due to the reported instability of ACTH, it is recommended to transfer centrifuged plasma into cryovials; however, in practice, cryovials are infrequently used, and serum (red-top) tubes are used instead. This study investigated whether this procedure affects ACTH concentrations and the diagnosis of PPID. Methods: This was a cohort study. Blood was collected into EDTA tubes from 9 horses with PPID and 7 controls. After centrifugation, plasma was either aliquoted into a cryovial or into a serum tube. Samples were stored at 4 and 20 °C with ACTH concentrations measured using a chemiluminescent assay at 2, 24, and 48 hours after collection. Data were analyzed using a 2-way repeated measures ANOVA with P < .05 considered significant. Results: There was a significant effect of time on ACTH concentrations in horses with PPID at 4 and 20 °C and in all horses at 20 °C with decreasing ACTH concentrations over time; however, no significant effect of storing plasma in a serum tube was detected. Three horses diagnosed with PPID would have had a different classification if the samples had been kept at 20 °C for 24 or 48 hours. Conclusions: Time but not storage of plasma in serum tubes decreases the measured ACTH concentration in horses with PPID. Clinical Relevance: Transferring plasma into serum tubes does not significantly alter the measured ACTH concentrations; however, time between collection and analysis might lead to erroneous diagnoses.
Language: English
Subfield: Physiology
Field: Medicine
Domain: Health Sciences
Open Access status: diamond
OpenAlex ID: W4407200669