Using the lower limit of normal for the FEV1/FVC ratio reduces the misclassification of airway obstruction

Abstract

Aim: The prevalence of airway obstruction varies widely with the definition used. Objectives: To study differences in the prevalence of airway obstruction when applying four international guidelines to three population samples using four regression equations. Methods: We collected predicted values for forced expiratory volume in 1 s/forced vital capacity (FEV 1 /FVC) and its lower limit of normal (LLN) from the literature. FEV 1 /FVC from 40 646 adults (including 13 136 asymptomatic never smokers) aged 17-90+years were available from American, English and Dutch population based surveys. The prevalence of airway obstruction was determined by the LLN for FEV 1 /FVC, and by using the Global Initiative for Chronic Obstructive Lung Disease (GOLD), American Thoracic Society/European Respiratory Society (ATS/ERS) or British Thoracic Society (BTS) guidelines, initially in the healthy subgroup and then in the entire population. Results: The LLN for FEV 1 /FVC varied between prediction equations (57 available for men and 55 for women), and demonstrated marked negative age dependency. Median age at which the LLN fell below 0.70 in healthy subjects was 42 and 48 years in men and women, respectively. When applying the reference equations (Health Survey for England 1995-1996, National Health and Nutrition Examination Survey (NHANES) III, European Community for Coal and Steel (ECCS)/ERS and a Dutch population study) to the selected population samples, the prevalence of airway obstruction in healthy never smokers aged over 60 years varied for each guideline: 17-45% of men and 7-26% of women for GOLD; 0-18% of men and 0-16% of women for ATS/ERS; and 0-9% of men and 0-11% of women for BTS. GOLD guidelines caused false positive rates of up to 60% when applied to entire populations. Conclusions: Airway obstruction should be defined by FEV 1 /FVC and FEV 1 being below the LLN using appropriate reference equations.Chronic obstructive pulmonary disease (COPD) is a major public health concern as a cause of chronic morbidity and mortality.

Debating the definition of airflow obstruction: time to move on?

“…As asthma is a disease of predominantly young people, the 0.70 criterion may, therefore, fail to diagnose many asthmatics as having obstruction, whereas in COPD, which is a disease of predominantly older people, the opposite is true; namely, too many may get the diagnosis of airflow obstruction without having it. FEV1/FVC declines with age [7], mainly due to an age-dependent loss of elastic fibres in the lungs, which reduces the elastic recoil of lung tissue. This is not per se a pathological process and so any consequent drop in FEV1/FVC cannot simply be ascribed to a disease such as COPD.…”

“…They reported ,20% misclassification in older age groups. SWANNEY et al [7] calculated false-positive test results as a percentage of all positive test results for airway obstruction in three large population-based samples of adults, including smokers and subjects with respiratory symptoms. They found that the LLN varied between prediction equations (57 equations available for males and 55 for females) and applying the GOLD fixed criterion of FEV1/FVC ,0.70 [4] caused false-positive rates of up to 60% when applied to entire populations.…”

Proposición de nuevas ecuaciones para calcular valores espirométricos de referencia en población chilena adulta: Sociedad Chilena de Enfermedades Respiratorias (SER)

“…Este concepto ha sido ampliamente difundido [41][42][43][44] , generando controversia respecto de la definición de EPOC propuesta por GOLD, que sugiere su diagnóstico cuando la relación VEF 1 /CVF es inferior a 70%, sin importar la edad.…”

Models for estimating projections for the prevalence and disease burden of chronic obstructive pulmonary disease (COPD): systematic review protocol

“…The nearest is the use of the European Coal and Steel Workers Population to provide percent predicted FEV 1 values; however, this population was standardised over 20 years ago and is based on a working white European population without ethnic minorities. [11][12][13] Similarly, younger people (age 30-40 years) with larger FVC values and greater respiratory reserve may already have sustained COPD-type damage to their lungs before they reach the <0.7 ratio threshold, so at this end of the age range there is a risk of under-diagnosis of COPD. 13 The debate regarding the diagnosis of COPD is more than just a debate over spirometry thresholds.…”

“…[11][12][13] Similarly, younger people (age 30-40 years) with larger FVC values and greater respiratory reserve may already have sustained COPD-type damage to their lungs before they reach the <0.7 ratio threshold, so at this end of the age range there is a risk of under-diagnosis of COPD. 13 The debate regarding the diagnosis of COPD is more than just a debate over spirometry thresholds. As many developing countries do not have access to spirometry or even to a reliable power supply, the usefulness of such diagnostic thresholds is limited.…”