Special reports from Li Zha, PhD, DABCC, Associate Director of Clinical Chemistry, University of Rochester Medical Center, Assistant Professor of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry (Current Address: Beth Israel Deaconess Medical Center); Qian Sun, PhD, DABCC, Technical Director of Automated Chemistry, Beaumont Health, Assistant Professor of Pathology, Oakland University William Beaumont School of Medicine; Jieli Shirley Li, MD, PhD, DABCC, NRCC. Co-Director of Clinical Chemistry and Toxicology Laboratory, Wexner Medical Center, Assistant Professor of Pathology, The Ohio State University.
Accurately interpreting the cosyntropin stimulation test requires method- and assay-specific cortisol cutoffs. Compared to the threshold of 18 μg/dL initially established for polyclonal antibody-based immunoassays, lower cutoffs have been proposed for assays that use more specific monoclonal antibodies, e.g., the Roche Elecsys II assay. However, diagnostic cutoffs appropriate for other monoclonal antibody-based cortisol assays were unavailable.
In the July 2022 issue of Endocrine Practice, the official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists, collaborators from three academic medical centers reported the establishment of cortisol thresholds specific to the monoclonal antibody-based Abbott Architect immunoassay. The significant inter-assay variability in cortisol measurement was first noted after an instrument update in the Beaumont Hospital Laboratory. Subsequently, serum cortisol levels from 50 patients with suspected adrenal insufficiency who underwent the cosyntropin stimulation test were measured using three immunoassays: Abbott Architect (Beaumont Health), Siemens Centaur (Wexner Medical Center, Ohio State University), and Roche Elecsys II (University of Rochester Medical Center).
The cortisol measurements by Abbott Architect were comparable to those from liquid chromatography-tandem mass spectrometry and Roche but significantly lower than those from Siemens Centaur, which uses a polyclonal antibody. The optimized cortisol threshold for the Abbott Architect assay was determined to be 14.6 μg/dL at 60 minutes after cosyntropin stimulation (sensitivity, 92%; specificity, 96%) and 13.2 μg/dL at 30 minutes after stimulation (sensitivity, 100%; specificity, 89%).
Utilizing assay-specific cortisol cutoffs will be critical for reducing misclassification and overtreatment in patients with suspected adrenal insufficiency.
促肾上腺素刺激试验用于诊断肾上腺功能不全时特异性检测方法临界值的设定
促肾上腺素刺激试验报告的正确解读需要用特异检测方法设定皮质醇的临界值。最初用多克隆抗体的免疫测定法建立的临界值是 18 μg/dL。相比于早期的检测方法，用更特异的单克隆抗体的测定法可以达到较低的临界值， 比如 Roche Elecsys II 测定法。目前除了Roche Elecsys II 测定法，其他使用单克隆抗体的免疫测定法还没有设定用于诊断的皮质醇水平临界值。
来自三个学术医学中心的合作者报道了使用Abbott Architect 单克隆抗体免疫测定法对皮质醇临界值水平的设定。该报道发表在美国内分泌学会和美国临床内分泌学家协会的官方期刊《内分泌实践》2022 年 7 月刊。先前，密歇根 Beaumont 医院实验室在仪器更新时发现皮质醇具有明显的批间差异。为了进一步了解其导致的临床影响，该报道合作者用三种免疫测定法测量了 50 名疑似肾上腺功能不全患者（这些患者都接受了促肾上腺素刺激试验）的血清皮质醇水平并进行比较。这三种免疫测定法分别是：Abbott Architect（Beaumont Health）、Siemens Centaur（俄亥俄州立大学韦克斯纳医学中心）和 Roche Elecsys II（罗彻斯特大学医疗中心）。
结果显示，Abbott Architect 的皮质醇测量与液相色谱-串联质谱法和Roche Elecsys II的测量结果很接近，但明显低于Siemens Centaur的多克隆抗体测定法。 Abbott Architect 测定得到的优化后皮质醇临界值被设定在促肾上腺素刺激后 60 分钟14.6 μg/dL（灵敏度，92%；特异性，96%）以及刺激后30分钟 13.2 μg/dL（灵敏度，100%；特异性，89%）。
该研究证明对疑似肾上腺功能不全的患者，用不同免疫测定法建立其对应皮质醇临界值水平，对减少误诊率以及过度治疗至关重要。
Reference:
Zha, L., Li, J., Krishnan, S. M., Brennan, M. R., Zhang, Y. V., Povse, P., Kerlin, R., Shively, K., Oleksik, F., Williams, J., Sykes, E., & Sun, Q. (2022). New Diagnostic Cutoffs for Adrenal Insufficiency After Cosyntropin Stimulation Using Abbott Architect Cortisol Immunoassay. Endocrine practice: official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists, 28(7), 684–689. https://doi.org/10.1016/j.eprac.2022.04.003
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