Schermer T R J, Smeele I J M, Thoonen B P A, Lucas A E M, Grootens J G, van Boxem T J, Heijdra Y F, van Weel C
Dept of General Practice, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Eur Respir J. 2008 Oct;32(4):945-52. doi: 10.1183/09031936.00170307. Epub 2008 Jun 11.
The aim of the present study was to establish the agreement between two recommended definitions of airflow obstruction in symptomatic adults referred for spirometry by their general practitioner, and investigate how rates of airflow obstruction change when pre-bronchodilator instead of post-bronchodilator spirometry is performed. The diagnostic spirometric results of 14,056 adults with respiratory obstruction were analysed. Differences in interpretation between a fixed 0.70 forced expiratory volume in one second (FEV(1))/forced vital capacity (FVC) cut-off point and a sex- and age-specific lower limit of normal cut-off point for this ratio were investigated. Of the subjects, 53% were female and 69% were current or ex-smokers. The mean post-bronchodilator FEV(1)/FVC was 0.73 in males and 0.78 in females. The sensitivity of the fixed relative to the lower limit of normal cut-off point definition was 97.9%, with a specificity of 91.2%, positive predictive value of 72.0% and negative predictive value of 99.5%. For the subgroup of current or ex-smokers aged > or =50 yrs, these values were 100, 82.0, 69.2 and 100%, respectively. The proportion of false positive diagnoses using the fixed cut-off point increased with age. The positive predictive value of pre-bronchodilator airflow obstruction was 74.7% among current or ex-smokers aged > or =50 yrs. The current clinical guideline-recommended fixed 0.70 forced expiratory volume in one second/forced vital capacity cut-off point leads to substantial overdiagnosis of obstruction in middle-aged and elderly patients in primary care. Using pre-bronchodilator spirometry leads to a high rate of false positive interpretations of obstruction in primary care.
本研究的目的是确定全科医生转诊进行肺活量测定的有症状成年人中，两种推荐的气流受限定义之间的一致性，并研究当进行支气管扩张剂前而非支气管扩张剂后肺活量测定时气流受限率如何变化。分析了14056名患有呼吸障碍的成年人的诊断性肺活量测定结果。研究了固定的一秒用力呼气量（FEV₁）/用力肺活量（FVC）截断点为0.70与该比率的性别和年龄特异性正常下限截断点之间解释的差异。受试者中，53%为女性，69%为当前吸烟者或既往吸烟者。男性支气管扩张剂后FEV₁/FVC的平均值为0.73，女性为0.78。固定截断点相对于正常下限截断点定义的敏感性为97.9%，特异性为91.2%，阳性预测值为72.0%，阴性预测值为99.5%。对于年龄≥50岁的当前吸烟者或既往吸烟者亚组，这些值分别为100%、82.0%、69.2%和100%。使用固定截断点的假阳性诊断比例随年龄增加。在年龄≥50岁的当前吸烟者或既往吸烟者中，支气管扩张剂前气流受限的阳性预测值为74.7%。当前临床指南推荐的固定一秒用力呼气量/用力肺活量截断点为0.70，导致基层医疗中中年和老年患者的阻塞性疾病过度诊断严重。在基层医疗中，使用支气管扩张剂前肺活量测定会导致气流受限的假阳性解释率很高。
