ROC曲线评价N端脑钠肽前体对撤机结局的预测价值

目的 应用受试者工作特征(ROC)曲线评价血浆氨基末端脑钠肽前体(NT-proBNP)对机械通气患者撤机结局的预测价值.方法 回顾性分析广东省人民医院ICU 2008年6月至2010年1月达到撤机标准并行撤机的患者.依撤机结局分为撤机成功组和失败组,以成组t检验及x2检验比较两组间年龄、性别及撤机前NT-proBNP对数值(Lg NT-proBNP);绘制ROC曲线,评价撤机前NT-proB-NP水平对撤机结局的预测价值.结果 共入选160例患者,成功组106例,失败组54例.撤机成功组年龄(岁)相对较轻(63.17±17.00)vs.(71.28±12.56),t=2.063,P=0.024],两组性别差异无统计学意义(χ2=0.06,P＞0.05).撤机失败组NT-proBNP水平明显高于成功组(Lg NT-proBNP:2.80±0.72,3.75±0.56,t=2.351,P=0.014);NT-proBNP预测撤机失败的ROC曲线下面积为0.855±0.036(95%CI=0.784～0.925),其预测撤机失败的截点值为3635.5 pg/mL,此值下的Youden指数为0.60,正确百分率为82.5%,敏感性为75%,特异性为84.7%,阳性似然比4.90,阴性似然比0.295,Kappa 值为0.62.结论 撤机前NT-proBNP值对撤机结局有一定的预测价值,可作为撤机筛查指标之一.

Application of receiver operating characteristic curve in the evaluation of predictive value of serum NT-proBNP in weaning outcome of patients with mechanical ventilation

Objective To evaluate the value of NT-proBNP in predicting weaning outcomes of the patients with mechanical ventilation by using the receiver operating characteristic (ROC)curve. Method The data of patients after the weaning of mechanical ventilation and spontaneous breathing trial (SBT) in the intensive care unit,from July 2008 to January 2010, were retrospective reviewed. All patients were divided into the success group and failure group as per the outcomes of weaning. Demographics and the serum NT-proBNP levels measured before weaning were compared between two groups with Student t -test and Chi-square test. The ROC curve was drawn to evaluate the value of serum NT-proBNP in predicting outcomes after weaning. Results A total of 160 patients were eligible for inclusion in the study, and there were 106 cases in success group and 54 cases in failure group.Compared with the failure group, the patients of success group were younger (63.17 ± 17.00 vs. 71.28 ± 12.56,t = 2.063,P =0.024), and no difference in gender (χ2 = 0.06, P ＞ 0.05). The NT-proBNP levels of failure group were significantly higher than those of success group (Lg NT-proBNP 2.80 ± 0.72 vs. 3.75 ± 0.56, t =2.351,P =0.014). The area under cure (AUC) of the ROC cure of NT-proBNPto predict the failure of weaning was 0.855 ±0.036 (95%CI0.784 ～ 0.925) when the cut-off level of NT-proBNP was 3635.5 pg/mL. And, this NT-proBNP level had a followed predictive efficiency in weaning outcome (Youden's index: 0. 60, accuracy:82.5%, sensitivity: 75%, specificity: 84.7%, positive likelihood ratio: 4.90, negative likelihood ratio:0.295,Kappa value: 0.62). Conclusions The levels of NT-proBNP before weaning have predictive value in weaning outcome, and it may be used as one of the screening indicators for weaning.