VA Palo Alto Health Care System/Stanford University, Palo Alto CA 94304, USA.
J Card Fail. 2010 Jan;16(1):76-83. doi: 10.1016/j.cardfail.2009.08.009. Epub 2009 Sep 26.
The ventilatory threshold (VT) is usually determined by visual assessment of the point where the rate of elimination of carbon dioxide (VCO(2)) increases nonlinearly with respect to oxygen uptake (VO(2)) (the V-Slope method). We quantified the reliability of VT determination using data from a multicenter study in patients with heart failure.
The Fix-Heart Failure-5 study of cardiac contractility modulation enrolled 428 patients from 50 centers in the United States. Cardiopulmonary exercise tests were performed at baseline and 12, 24, and 50 weeks after randomization, which provided 1679 tests. The VT was determined from each test in a core laboratory by 2 independent readers. VT could not be determined for 276 tests (16.4% indeterminate). Inter-observer variability (quantified by the 95% limits of agreement, LoA, expressed as a percent of the mean value) was 20.2% between the 2 readers, with a coefficient of variation (CV) of 7.3%. Intra-observer variability was assessed by resubmitting (blinded) 179 tests to the same readers; the LoA was 24.7% for reader 1 and 16.9% for reader 2, with CVs of 6.1 and 8.9%, respectively. Ninety-one tests were submitted to 2 additional readers at a second core lab. Inter-observer variability in the second lab was 26.7% with a CV of 9.6%. Inter-laboratory variability was 21.4%, with a CV of 7.7%.
Inter-observer, intra-observer, and inter-site variation in determining the VT should be considered when using the VT as an end point in clinical trials of heart failure.
通气阈（VT）通常通过观察二氧化碳排除率（VCO2）相对于摄氧量（VO2）呈非线性增加的点来确定（V-斜率法）。我们使用心力衰竭患者多中心研究的数据来量化 VT 确定的可靠性。
心脏收缩调节的固定心力衰竭-5 研究在美国 50 个中心招募了 428 名患者。在随机分组后 12、24 和 50 周进行心肺运动测试，共提供 1679 次测试。VT 由核心实验室的 2 位独立读者从每次测试中确定。有 276 次测试（16.4%不确定）无法确定 VT。观察者间变异性（以 95%一致性界限表示，LOA，以平均值的百分比表示）在 2 位读者之间为 20.2%，变异系数（CV）为 7.3%。通过将 179 次测试重新提交给同一读者（盲法）来评估观察者内变异性；读者 1 的 LOA 为 24.7%，读者 2 的 LOA 为 16.9%，CV 分别为 6.1%和 8.9%。将 91 次测试提交给第二个核心实验室的另外 2 位读者。第二个实验室的观察者间变异性为 26.7%，CV 为 9.6%。实验室间变异性为 21.4%，CV 为 7.7%。
在心力衰竭临床试验中使用 VT 作为终点时，应考虑确定 VT 时的观察者间、观察者内和站点间差异。
