Institute of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Leahurst, Cheshire CH64 7TE, UK.
Institute of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Leahurst, Cheshire CH64 7TE, UK.
Vet J. 2019 Oct;252:105351. doi: 10.1016/j.tvjl.2019.105351. Epub 2019 Aug 5.
Fasting horses for measurement of basal serum insulin concentration (fasting insulin; FI) has been recommended to standardise testing for insulin dysregulation (ID), yet limited data exist comparing it to dynamic tests. This study aimed to compare FI with the combined glucose-insulin test (CGIT) in horses suspect for ID. We hypothesised that FI would have poor sensitivity for detecting ID compared to CGIT using conventional cut-offs. Records were retrieved from CGITs performed in horses fasted for approximately 8h. Serum insulin and glucose concentrations were measured before and for 150min following an IV bolus of glucose followed by insulin. Correlations between FI and CGIT values were assessed. Youden's index analysis was used to determine the optimal cut-off for FI. Logistic regression and Mann-Whitney U tests were used to determine factors affecting the results. CGITs (n=130) from 62 horses were evaluated. Compared to CGIT, sensitivity and specificity of FI for diagnosis of ID were 14.6% and 100% at a cut-off of 20μIU/mL and 63.4% and 87.2% at a cut-off of 5.2μIU/mL, respectively. FI was significantly correlated with insulin at 45min (r=0.66) and 75min (r=0.72); area under the curve for insulin (AUC; r=0.67); glucose at 45min (r=0.53); and AUC (r=0.50). Obesity was significantly associated with increased odds of a positive CGIT and horses with a positive CGIT were significantly older (P<0.05). In conclusion, FI correlated well with CGIT results and had adequate sensitivity and specificity at lower cut-offs, despite poor sensitivity at conventional cut-off values. Further research to derive cut-off values relevant to the fasting period is warranted.
禁食马匹以测量基础血清胰岛素浓度（空腹胰岛素；FI）已被推荐用于标准化胰岛素失调（ID）的检测，但比较其与动态检测的相关数据有限。本研究旨在比较 FI 与联合葡萄糖-胰岛素试验（CGIT）在疑似 ID 的马匹中的应用。我们假设与 CGIT 相比，使用传统截止值时，FI 检测 ID 的敏感性较差。从大约禁食 8 小时的 CGIT 中检索记录。在静脉注射葡萄糖和胰岛素后 150 分钟内，测量血清胰岛素和葡萄糖浓度。评估 FI 和 CGIT 值之间的相关性。使用约登指数分析确定 FI 的最佳截止值。使用逻辑回归和曼-惠特尼 U 检验确定影响结果的因素。评估了 62 匹马的 130 次 CGIT。与 CGIT 相比，FI 诊断 ID 的敏感性和特异性在截止值为 20μIU/mL 时分别为 14.6%和 100%，在截止值为 5.2μIU/mL 时分别为 63.4%和 87.2%。FI 与 45 分钟（r=0.66）和 75 分钟（r=0.72）时的胰岛素、胰岛素的曲线下面积（AUC；r=0.67）、45 分钟时的葡萄糖（r=0.53）和 AUC（r=0.50）呈显著相关。肥胖与 CGIT 阳性的几率增加显著相关，而 CGIT 阳性的马匹年龄显著更大（P<0.05）。总之，FI 与 CGIT 结果相关性良好，在较低的截止值下具有足够的敏感性和特异性，尽管在传统截止值下敏感性较差。需要进一步研究以确定与禁食期相关的截止值。
