Abstract
BackgroundCurrent COPD guidelines advocate a fixed < 0.70 FEV1/FVC cutpoint to define airflow obstruction. We compared rate of lung function decline in respiratory symptomatic 40+ subjects who were 'obstructive' or 'non-obstructive' according to the fixed and/or age and gender specific lower limit of normal (LLN) FEV1/FVC cutpoints.MethodsWe studied 3,324 respiratory symptomatic subjects referred to primary care diagnostic centres for spirometry. The cohort was subdivided into four categories based on presence or absence of obstruction according to the fixed and LLN FEV1/FVC cutpoints. Postbronchodilator FEV1 decline served as primary outcome to compare subjects between the respective categories.Results918 subjects were obstructive according to the fixed FEV1/FVC cutpoint; 389 (42%) of them were non-obstructive according to the LLN cutpoint. In smokers, postbronchodilator FEV1 decline was 21 (SE 3) ml/year in those non-obstructive according to both cutpoints, 21 (7) ml/year in those obstructive according to the fixed but not according to the LLN cutpoint, and 50 (5) ml/year in those obstructive according to both cutpoints (p = 0.004).ConclusionThis study showed that respiratory symptomatic 40+ smokers and non-smokers who show FEV1/FVC values below the fixed 0.70 cutpoint but above their age/gender specific LLN value did not show accelerated FEV1 decline, in contrast with those showing FEV1/FVC values below their LLN cutpoint.
Highlights
Current Chronic obstructive pulmonary disease (COPD) guidelines advocate a fixed < 0.70 forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) cutpoint to define airflow obstruction
Study subjects The total study population consisted of 5,215 respiratory symptomatic subjects aged ≥ 40 years who had been referred for spirometry by their general practitioner (GP) and for whom complete data for three measurements in at least one year were available (Figure 1). 1,241 subjects were in different categories based on the fixed and lower limit of normal (LLN) definitions for airflow obstruction during their baseline and final visits
Analysis of our base case population showed that the annual postbronchodilator FEV1 decline in discordant subjects was very similar to subjects who were non-obstructive according to both definitions (i.e., LLNFixed- category), and that it was less than half the rate of decline observed in subjects with FEV1/FVC values below their age-specific LLN cutpoint
Summary
Current COPD guidelines advocate a fixed < 0.70 FEV1/FVC cutpoint to define airflow obstruction. Because the majority of COPD patients are diagnosed and managed in primary care [15] and primary care doctors need to differentiate between various underlying causes for the respiratory symptoms a patient presents with (i.e., asthma, COPD, congestive heart failure, and a wide range of other causes), it is especially important for them to know which cutpoint is preferred when assessing the presence (or absence) of airflow obstruction This is even more important because in elderly patients co-morbid conditions are often present, and misattribution of a patient’s symptoms (e.g., dyspnoea) to COPD could lead to inappropriate or delayed treatment
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