Contemporary interpretation of lung function test results
Nederlands Tijdschrift voor Geneeskunde , Volume 158 - Issue 13
Objective: To assess the effects on the interpretation of spirometric test results (forced expiratory volume in 1 s, FEV1; forced vital capacity, FVC) of a change from predicted values from Zapletal and those of the European Community for Steel and Coal (ECSC) to those issued by the Global Lung Function Initiative (GLI), which have been endorsed by six large international respiratory societies. Design: Data from 1,012 children and adolescents (6-17 years, 47.1% girls), and 4,653 adults (18-91 years, 48,6% females), obtained during routine spirometric assessment of lung disease in inpatients and outpatients in Erasmus Medical Centre (a tertiary hospital), were available pre- and post-bronchodilator (children salbutamol 4*100 μg, adults salbutamol 400 or 800 μg aerosol,). They served to compare the prevalence rate of spirometric airway obstruction and low FVC using prediction equations from Zapletal, ECSC and GLI, as well as the criterion for airways obstruction advocated by the Global Initiative for Chronic Obstructive Lung Disease (GOLD). Methods: Subjects were classified as obstructive if the FEV1/FVC ratio was below the 5th percentile, constituting the lower limit of normal (LLN) and corresponding with a z-score of -1.64. GOLD obstructive lung disease was defined as FEV1/FVC <0.70 post-bronchodilator. A low FVC was diagnosed if FEV1/FVC >0.85 but FVC Results: Predicted values for FEV1 and FVC from Zapletal and the ECSC were too low, and the former connected poorly at the transition from adolescence to adulthood. The overall prevalence rate of airways obstruction pre-bronchodilator in children, using Zapletal and GLI predicted values pre-bronchodilator was 21.3 and 22.4% respectively, and 12.7 and 13.5% respectively post-bronchodilator. Corresponding values in adults using ECSC and GLI prediction equations were 36.3 and 34.3% pre-bronchodilator, and 30.8 and 29.7% post-bronchodilator respectively. Applying the GOLD criterion 36.2% of patients had airways obstruction post-broncho?dilator. All prevalence rates were statistically different (X2 test, p <0.0001). In adults younger than 45 years the GOLD definition leads to underesti?mating airways obstruction on average by 13.4% and 13.6% pre- and post-broncho?dilator, respectively, and to overestimating it in older adults by 31.8 and 34.0% pre- and post-bronchodilator respectively, with a pronounced age-related bias particularly in the elderly. Applying the GOLD definition, of the adults clinically categorised as having asthma, 21.0% had irreversible airways obstruction.Because the predicted value for FVC according to the ECSC is systematically lower than that according to the GLI, a low FVC was on average more prevalent using GLI equations, with greater discrepancies in younger adults. Conclusion: Adopting the GLI prediction equations for spirometric indices will lead to slight changes in the prevalence rate of airways obstruction in children and adults. Overall the benefits of adopting the GLI equations are that they seamlessly bridge the 3-95 year age span, are applicable to various ethnic groups, and take into account that variability in predicted values varies with age. The proposed 90% reference interval implies a lower limit of normal characterised by a z-score of -1.64. The great advantage of z-scores is that they allow comparison of cross-sectional data and serial measurements without age, height, sex and ethnic group related biases associated with the use of percent of predicted and a fixed lower limit of normal of the FEV1/FVC ratio.
|Nederlands Tijdschrift voor Geneeskunde|
|Organisation||Erasmus MC: University Medical Center Rotterdam|
Quanjer, P.H, Stam, H.J, Mertens, F.W, de Jongste, J.C, Chavannes, N.H, & Hoogsteden, H.C. (2014). Contemporary interpretation of lung function test results. Nederlands Tijdschrift voor Geneeskunde, 158(13). Retrieved from http://hdl.handle.net/1765/88538