The effects of sample handling and N-phenylmaleimide on concentration of adrenocorticotrophic hormone in equine plasma.

The research article discusses the stability of adrenocorticotrophic hormone (ACTH) in equine blood samples and the impact of certain variables on its concentration. The study tested if applying a protease inhibitor, N-phenylmaleimide, and different sample handling methods influenced ACTH levels. It concludes that irrespective of the sample handling method, reliable results can be obtained by testing ACTH concentration up to 48 hours post-collection, and N-phenylmaleimide doesn’t impact ACTH concentration significantly.

Research Methods

• Sampling: Venous blood was collected from two groups of horses – 8 healthy horses and 8 horses suffering from pituitary pars intermedia dysfunction (PPID), a condition that significantly impacts ACTH concentrations.
• Baseline Measurement: The base level of ACTH was determined immediately after collection using a chemiluminescent assay.
• Sample Treatment: Each blood sample was subjected to one of the three methods: i) Immediate centrifugation, ii) Immediate centrifugation with the addition of N-phenylmaleimide, iii) Allowing the sample to separate by gravity, followed by the addition of N-phenylmaleimide.
• Storage and Analysis: All treated samples were stored at 22°C and then analysed at time intervals of 4, 8, 24, and 48 hours post-collection. A linear mixed-effects model and Bland-Altman analyses were utilised to assess the data.

Research Findings

• ACTH Concentration: The study revealed no significant effects of the plasma treatment on changes in ACTH concentration. However, horse health status and time post-collection had a significant impact.
• Health Status and Time: ACTH concentration decreased significantly in PPID horses between 4 to 8 hours after blood collection. However, in healthy horses, the decrease in ACTH concentration was not significant.
• Sample Treatment: Allowing blood samples to separate by gravity instead of centrifugation did not significantly influence ACTH concentration, suggesting no need for immediate processing of samples.
• Use of N-phenylmaleimide: The protease inhibitor N-phenylmaleimide had no significant effect on ACTH concentration, suggesting it is not beneficial in preserving ACTH levels in the samples.

Research Conclusion

• ACTH Test Results: Clinicians can obtain reliable results even when ACTH concentration is measured up to 48 hours after sample collection. This is helpful as it suggests flexibility with the timing of sample analyses without compromising the results.
• Effect of N-phenylmaleimide: The protease inhibitor does not significantly affect the results; thus, it doesn’t play a significant role in preserving ACTH in equine plasma samples.
• Impact of Sample treatment: The way the plasma samples are processed, whether by gravity separation or by centrifugation, does not significantly influence the ACTH concentration—thus, streamlining the sample handling process.