The effect of freeze-thaw cycles on determination of immunoreactive plasma adrenocorticotrophic hormone concentrations in horses.
Authors: Hu Ke, Stewart Allison J, Yuen Ka Y, Hinrichsen Sophia, Dryburgh Elizabeth L, Bertin François-René
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary Plasma ACTH measurement remains the clinical cornerstone for diagnosing pituitary pars intermedia dysfunction (PPID) in horses, yet the hormone's notorious instability has long posed challenges for sample handling and transport. Ke and colleagues investigated whether repeated freeze-thaw cycles—a common occurrence when samples are batched, shipped, or re-analysed—compromise the accuracy of immunoreactive ACTH quantification. Through systematic exposure of equine plasma samples to multiple freeze-thaw cycles, the researchers assessed whether ACTH concentrations remained stable or degraded, with direct implications for diagnostic reliability. The findings revealed significant reductions in measured ACTH concentrations with successive freeze-thaw cycles, raising important questions about the validity of historical samples, multi-cycle shipping protocols, and batch testing procedures. For practitioners and laboratories submitting ACTH samples, this work underscores the critical importance of minimising freeze-thaw exposure, requesting single-use aliquots, and clarifying sample handling protocols with diagnostic facilities to ensure that borderline or equivocal results are not artefactually lowered by sample degradation rather than reflecting true endocrine status.
Read the full abstract on PubMed
Practical Takeaways
- •Minimize freeze-thaw cycles when collecting and storing plasma samples for ACTH testing to ensure accurate PPID diagnosis
- •Work with your diagnostic laboratory to confirm their sample handling protocols and whether they accept previously frozen samples
- •Consider fresh sample submission or single freeze protocols when possible, as repeated freezing degrades ACTH stability and may lead to unreliable results
Key Findings
- •ACTH is unstable in plasma samples and affected by freeze-thaw cycles
- •Multiple freeze-thaw cycles impact immunoreactive plasma ACTH concentration measurements
- •Sample handling procedures affect diagnostic test reliability for PPID diagnosis in horses