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,Andrew P Dickens,David A Fitzmaurice,Peymané Adab,Shamil Haroon,Alexandra Enocson,Rachel E Jordan,Alice J Sitch

doi:10.2147/copd.s146914

Abstract

BackgroundConsensus on the definition of airflow obstruction to diagnose COPD remains unresolved.MethodsWe undertook systematic case finding for COPD in primary care using the fixed ratio (FR) criterion (forced expiratory volume in 1 s/forced vital capacity [FEV1/FVC] <0.7) for defining airflow obstruction and also using the lower limit of normal (LLN). We then compared the clinical characteristics of those identified by the 2 criteria.ResultsA total of 3,721 individuals reporting respiratory symptoms were invited for spirometry. A total of 2,607 attended (mean age 60.4 years, 52.8% male, 29.8% current smokers) and 32.6% had airflow obstruction by FR (“FR+”) and 20.2% by LLN (“LLN+”). Compared with the LLN+/FR+ group, the LLN−/FR+ group (12.4%) was significantly older, had higher FEV1 and FEV1/FVC, lower COPD assessment test scores, and less cough, sputum, and wheeze, but was significantly more likely to report a diagnosis of heart disease (14.2% versus 6.9%, p<0.001). Compared with the LLN+/FR+ group, the LLN−/FR− group was younger, had a higher body mass index, fewer pack-years, a lower prevalence of respiratory symptoms except for dyspnea, and lower FVC and higher FEV1. The probability of known heart disease was significantly lower in the LLN+/FR+ group compared with those with preserved lung function (LLN−/FR−) (adjusted odds ratio 0.62, 95% CI: 0.43–0.90) but this was not seen in the LLN−/FR+ group (adjusted odds ratio 0.90, 95% CI: 0.63–1.29).ConclusionIn symptomatic individuals, defining airflow obstruction by FR instead of LLN identifies a significant number of individuals who have less respiratory and more cardiac clinical characteristics.

Highlights

COPD is the third leading cause of premature mortality and the fifth leading cause of disability adjusted life years globally.[1]
Since previous literature has suggested that use of the fixed ratio (FR) tends to include more patients with cardiovascular disease than the lower limit of normal (LLN) criteria,[6] we tested this hypothesis in our data using a logistic regression model with self-reported cardiovascular disease as the outcome, and LLN/ FR status as an independent variable with models derived adjusting for age, sex, smoking status, self-reported diabetes mellitus, and hypertension
Our study found that the prevalence of dyspnea was similar between individuals diagnosed with COPD by either diagnostic criterion whereas cough and sputum were less prevalent in the LLN−/FR+ group

Summary

Introduction

COPD is the third leading cause of premature mortality and the fifth leading cause of disability adjusted life years globally.[1] Huge efforts have been made to improve the diagnosis of COPD in primary care. The definition of COPD remains an unresolved issue with controversy remaining about the criteria for defining airflow obstruction. The Global Initiative for Obstructive Lung Disease (GOLD) and the National Institute for Health and Care Excellence (NICE) in the UK recommend the use of a fixed ratio (FR) of forced expiratory volume in 1 s (FEV1) to forced vital. Dovepress capacity (FVC) of 0.7 as the diagnostic threshold for airflow obstruction.[2,3] this criterion does not take into consideration that FEV1/FVC declines with age and differs between the sexes and by ethnicity.[4]. Consensus on the definition of airflow obstruction to diagnose COPD remains unresolved

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