Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Equine Vet J. 2024 Mar;56(2):291-298. doi: 10.1111/evj.13991. Epub 2023 Aug 30.
The thyrotropin-releasing hormone (TRH) stimulation test is used to diagnose pituitary pars intermedia dysfunction (PPID) using 10- or 30-min protocols. Imprecise sampling time for the 10-min protocol can lead to misdiagnoses.
To determine the effect of imprecise sampling time for the 30-min protocol of the TRH stimulation test.
In vivo experiment.
Plasma immunoreactive adrenocorticotropin (ACTH) concentrations were measured 9, 10, 11, 29, 30 and 31 min after intravenous administration of 1 mg of TRH in 15 control and 12 PPID horses. Differences in ACTH concentrations between sampling times, variability in ACTH concentrations between protocols, and diagnostic classification of PPID were assessed using Friedman's test, Bland-Altman plots, and Fisher's exact test, respectively, with 95% confidence intervals reported and significance set at p < 0.05.
Imprecise sampling time resulted in variable ACTH concentrations, but significant differences in absolute ACTH concentrations were not detected for imprecise sampling within each protocol or between protocols. Imprecise sampling changed PPID diagnostic classification for 3/27 (11 [4-28] %) horses for both protocols. Using the 30-min protocol as a reference, 1/12 (8 [1-35] %) horses returned a negative test result and 5/12 (42 [19-68] %) horses returned equivocal test results that would be considered positive in practice due to the presence of supportive clinical signs.
Limited sample size and inter-horse variability reduced the ability to detect small but potentially relevant differences.
Overall, the impact of imprecise sampling was not significantly different between the 10- and 30-min TRH stimulation test protocols. However, diagnostic classification for PPID would have varied between the 10- and 30-min protocols in this population, if clinical signs had been ignored. Precise timing during TRH stimulation tests and contextual interpretation of ACTH concentrations remain fundamental for the diagnosis of PPID.
促甲状腺素释放激素（TRH）刺激试验用于通过 10 分钟或 30 分钟方案诊断垂体中叶功能减退症（PPID）。10 分钟方案中采样时间不精确可能导致误诊。
确定 TRH 刺激试验 30 分钟方案中采样时间不精确的影响。
体内实验。
在 15 匹对照马和 12 匹 PPID 马中，静脉注射 1mgTRH 后 9、10、11、29、30 和 31 分钟测量血浆免疫反应性促肾上腺皮质激素（ACTH）浓度。使用 Friedman 检验、Bland-Altman 图和 Fisher 确切检验分别评估采样时间之间的 ACTH 浓度差异、方案之间的 ACTH 浓度变异性以及 PPID 的诊断分类，置信区间为 95%，显著性设定为 p<0.05。
采样时间不精确导致 ACTH 浓度变化，但在每个方案内或两个方案之间均未检测到绝对 ACTH 浓度的显著差异。采样时间不精确改变了两个方案中 3/27（11[4-28]%）匹马的 PPID 诊断分类。以 30 分钟方案为参考，1/12（8[1-35]%）匹马的试验结果为阴性，5/12（42[19-68]%）匹马的试验结果为不确定，由于存在支持性临床症状，在实践中这些结果将被视为阳性。
样本量有限和个体间变异性降低了检测小但潜在相关差异的能力。
总体而言，在这组马中，10 分钟和 30 分钟 TRH 刺激试验方案之间采样时间不精确的影响没有显著差异。然而，如果忽略临床症状，这两种方案的 PPID 诊断分类将会有所不同。在 TRH 刺激试验中精确计时以及对 ACTH 浓度进行背景解释仍然是诊断 PPID 的基础。
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