Serum insulin concentration in horses: Effect of storage and handling.
Authors: Carslake Harry, Karikoski Ninja, Pinchbeck Gina, McGowan Catherine
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary When investigating equine endocrinopathic conditions such as insulin dysregulation and equine metabolic syndrome, serum insulin measurement is a crucial diagnostic tool, yet clinical laboratories are not always able to process samples immediately. Carslake and colleagues examined whether delaying analysis affected the reliability of insulin assays by storing blood samples from 14 horses at room temperature for up to 72 hours either as whole blood or as separated serum, comparing these against the reference standard of immediate separation and freezing. Correlation coefficients remained excellent across all storage conditions (≥0.992), and whilst whole blood samples showed a small negative bias of 2.16 µIU/mL relative to serum, this magnitude of difference fell below clinical significance thresholds. Importantly, when results were interpreted against the two most commonly applied diagnostic cut-offs for equine insulin dysregulation, storage conditions did not alter diagnostic conclusions. These findings provide reassurance that minor delays in sample processing—whether due to transit time, weekend submissions, or laboratory scheduling—need not compromise the validity of insulin testing, allowing practitioners greater flexibility in sampling logistics without sacrificing diagnostic accuracy.
Read the full abstract on PubMed
Practical Takeaways
- •If immediate serum separation and freezing is unavailable, samples can be stored at room temperature for up to 72 hours without compromising diagnostic accuracy for endocrinopathy screening
- •Clinicians can confidently submit whole blood or serum samples to reference labs without requiring special handling or cooling during transport, improving logistics for field-based testing
- •Sample storage method does not affect whether results exceed diagnostic thresholds used for detecting endocrinopathic disease in horses
Key Findings
- •Serum insulin concentration showed excellent correlation (≥0.992) across all storage conditions tested
- •Samples stored as whole blood at room temperature for 72 hours showed a mean negative bias of 2.16 µIU/mL compared to immediate frozen serum, but this was not clinically significant
- •At two commonly used diagnostic cut-offs for endocrinopathy, storage method had no effect on clinical interpretation of results
- •Room temperature storage for 72 hours as either serum or whole blood has minimal effect on measured insulin values in horses