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Clinical characteristics of patients newly diagnosed with COPD by the fixed ratio and lower limit of normal criteria: a cross-sectional analysis of the TargetCOPD trial

Martin R Miller, Shamil Haroon, Rachel E Jordan, et al.
Int J Chron Obstruct Pulmon Dis 2018;13:1979–86
doi: 10.2147/COPD.S146914

Although chronic obstructive pulmonary disease (COPD) is the third leading cause of premature mortality, its definition remains in a state of controversy due to the criteria for defining airflow obstruction. The Global Initiative for Chronic Obstructive Lung Disease (GOLD) and the National Institute for Health and Care Excellence (NICE) apply the fixed ratio (FR) of forced expiratory volume in 1 second (FEV1) to forced vital capacity (FVC) of <70% as indicative of airflow obstruction, but this definition takes into account neither age, ethnicity nor gender.


The aim of this study was to compare the clinical characteristics of symptomatic patients in primary care with case-found COPD diagnosed when using the FR criterion with those identified when using the lower limit of normal (LLN; below the fifth percentile adjusted for age, gender, height and ethnic group).


The study consisted of a post-hoc cross-sectional analysis of data from TargetCOPD, which was a cluster-randomised controlled trial based in primary care that compared two approaches to COPD case finding against usual care. Those of the 32,811 case-finding arm of the TargetCOPD trial who responded to a questionnaire and attended a spirometry assessment (n=2607) were analysed for demographic characteristics, smoking status, symptoms, self-reported co-morbidities and quality of life.


The conclusion of the study was that the use of FR for defining airflow obstruction may lead to the inclusion of a significant number of older people with breathlessness as having COPD, who may instead have age-related changes in lung function in the presence of cardiovascular disease as the cause for their symptoms.

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