Reynolds R M, Bendall H E, Whorwood C B, Wood P J, Walker B R, Phillips D I
Medical Research Council Environmental Epidemiology Unit, University of Southampton, UK.
Clin Endocrinol (Oxf). 1998 Sep;49(3):307-10. doi: 10.1046/j.1365-2265.1998.00549.x.
The low dose dexamethasone suppression test (DST) has been used to detect subtle variations in the feedback suppression of the hypothalamic-pituitary-adrenal axis, which may contribute to the pathogenesis of several diseases including depression, the metabolic syndrome and coronary artery disease. Little is known about the reproducibility of this test, or whether the test can be combined with analysis of salivary cortisol which would offer a significant advantage over plasma in population studies.
A low dose DST was carried out in 29 healthy subjects (14 men, 15 women), aged 24-54 (mean 35.1) years, on two separate occasions 1-10 weeks apart. Following the administration of 0.25 mg dexamethasone (DXM) at 2200 h, plasma and saliva were sampled at 0830 h the next day. Cortisol was measured by radioimmunoassay in plasma and time-resolved immunofluorescent assay ('DELFIA') in saliva. Bland-Altman plots were produced for post-DXM plasma and salivary cortisol measures and used to derive a coefficient of repeatability for each measure, which describes the range of cortisol measurements within which 95% of repeated measurements will fall.
The baseline, pre-DXM cortisol concentrations were far more variable for saliva (mean 16.5, range 4.4-34 nmol/l) than for plasma (mean 407.5; range 232-958 nmol/l). Following DXM both measurements showed an approximately 30% suppression from baseline but the variability of salivary cortisol was much greater. From the Bland-Altman plots the 95% range for the differences about their mean was calculated and used as an indication of repeatability. For plasma 95% of differences were within 0.78 log units, indicating that a repeated measurement was approximately half as small or twice as large as the first. For saliva 95% of differences were within 1.64, indicating that a repeated measurement was approximately five times as small or five times as large as the first.
Assessment of dexamethasone suppression by salivary cortisol measurement is far less repeatable than the use of plasma cortisol. In the context of field studies of dexamethasone suppression, salivary cortisol measurements may only be appropriate for large numbers of subjects.
低剂量地塞米松抑制试验（DST）已被用于检测下丘脑 - 垂体 - 肾上腺轴反馈抑制的细微变化，这可能有助于包括抑郁症、代谢综合征和冠状动脉疾病在内的多种疾病的发病机制。关于该试验的可重复性，或者该试验是否可以与唾液皮质醇分析相结合（这在人群研究中相对于血浆具有显著优势），人们了解甚少。
对29名健康受试者（14名男性，15名女性）进行了低剂量DST，年龄在24 - 54岁（平均35.1岁），在相隔1 - 10周的两个不同时间进行。在22:00给予0.25毫克地塞米松（DXM）后，于次日08:30采集血浆和唾液样本。血浆中的皮质醇通过放射免疫测定法测量，唾液中的皮质醇通过时间分辨免疫荧光测定法（“DELFIA”）测量。针对DXM给药后的血浆和唾液皮质醇测量结果绘制了布兰德 - 奥特曼图，并用于得出每种测量方法的重复性系数，该系数描述了95%的重复测量结果将落入的皮质醇测量范围。
唾液的基线、DXM给药前皮质醇浓度（平均16.5，范围4.4 - 34纳摩尔/升）比血浆（平均407.5；范围232 - 958纳摩尔/升）的变化大得多。给予DXM后，两种测量结果均显示从基线水平大约抑制了30%，但唾液皮质醇的变异性要大得多。根据布兰德 - 奥特曼图计算了关于其均值的差异的95%范围，并将其用作重复性的指标。对于血浆，95%的差异在0.78对数单位以内，这表明重复测量值大约是第一次测量值的一半或两倍。对于唾液，95%的差异在1.64以内，这表明重复测量值大约是第一次测量值的五分之一或五倍。
通过测量唾液皮质醇评估地塞米松抑制的可重复性远低于使用血浆皮质醇。在地塞米松抑制的现场研究中，唾液皮质醇测量可能仅适用于大量受试者。
