1 Servicio de Urgencias and.
2 Unidad de Neumología, Hospital Universitario de Fuenlabrada, Fuenlabrada, Madrid, Spain.
Am J Respir Crit Care Med. 2017 Aug 1;196(3):298-305. doi: 10.1164/rccm.201611-2265OC.
Global Lung Function Initiative recommends reporting lung function measures as z-score, and a classification of airflow limitation (AL) based on this parameter has recently been proposed.
To evaluate the prognostic capacity of the AL classifications based on z-score or percentage predicted of FEV in patients with chronic obstructive pulmonary disease (COPD).
A cohort of 2,614 patients with COPD recruited outside the hospital setting was examined after a mean (± SD) of 57 ± 13 months of follow-up, totaling 10,322 person-years. All-cause mortality was analyzed, evaluating the predictive capacity of several AL staging systems.
Based on Global Initiative for Chronic Obstructive Lung Disease guidelines, 461 patients (17.6%) had mild, 1,452 (55.5%) moderate, 590 (22.6%) severe, and 111 (4.2%) very severe AL. According to z-score classification, 66.3% of patients remained with the same severity, whereas 23.7% worsened and 10.0% improved. Unlike other staging systems, patients with severe AL according to z-score had higher mortality than those with very severe AL (increase of risk by 5.2 and 3.9 times compared with mild AL, respectively). The predictive capacity for 5-year survival was slightly higher for FEV expressed as percentage of predicted than as z-score (area under the curve: 0.714-0.760 vs. 0.649-0.708, respectively). A severity-dependent relationship between AL grades by z-score and mortality was only detected in patients younger than age 60 years.
In patients with COPD, the AL classification based on z-score predicts worse mortality than those based on percentage of predicted. It is possible that the z-score underestimates AL severity in patients older than 60 years of age with severe functional impairment.
全球肺功能倡议建议将肺功能测量结果报告为 z 分数，并最近提出了一种基于该参数的气流受限（AL）分类方法。
评估基于 z 分数或预测的 1 秒用力呼气量（FEV）的 AL 分类在慢性阻塞性肺疾病（COPD）患者中的预后能力。
在平均（±标准差）随访 57±13 个月后，对来自医院外环境的 2614 例 COPD 患者队列进行了检查，总随访时间为 10322 人年。分析了全因死亡率，评估了几种 AL 分期系统的预测能力。
根据全球慢性阻塞性肺疾病倡议指南，461 例（17.6%）患者为轻度、1452 例（55.5%）为中度、590 例（22.6%）为重度和 111 例（4.2%）为极重度 AL。根据 z 分数分类，66.3%的患者仍处于相同严重程度，而 23.7%的患者恶化，10.0%的患者改善。与其他分期系统不同，根据 z 分数分类的重度 AL 患者的死亡率高于极重度 AL 患者（与轻度 AL 相比，风险分别增加了 5.2 和 3.9 倍）。FEV 以预测百分比表示的预测 5 年生存率略高于以 z 分数表示的预测生存率（曲线下面积：0.714-0.760 与 0.649-0.708）。仅在年龄小于 60 岁的患者中，才发现基于 z 分数的 AL 分级与死亡率之间存在严重程度依赖性关系。
在 COPD 患者中，基于 z 分数的 AL 分类预测死亡率比基于预测百分比的 AL 分类差。对于年龄大于 60 岁且功能严重受损的患者，z 分数可能低估了 AL 的严重程度。
