Treatable Traits in Misdiagnosed Chronic Obstructive Pulmonary Disease: Data from the Akershus Cardiac Examination 1950 Study.

Background: Chronic obstructive pulmonary disease (COPD) is often misdiagnosed. We aimed to estimate the prevalence of misdiagnosed COPD in middle-aged Norwegians, and to assess potentially treatable clinical traits in over- and undiagnosed individuals.

Methods and findings: The Akershus Cardiac Examination (ACE) 1950 Study is a population-based study of the 1950 birth cohort of Akershus county including 3706 participants aged 62-65 years at baseline. COPD was defined as a forced expiratory volume in 1 second (FEV₁) to forced vital capacity (FVC) ratio < lower limit of normal (LLN). Misdiagnosed COPD was defined according to self-reported COPD. A total of 259 (7.1%) participants had spirometry confirmed COPD. Of these, only 72 (28%) reported having COPD, thus 187 (72%) were undiagnosed. A total of 92 (2.5%) of the 164 particpants who reported having COPD had an FEV₁/FVC ratio ≥ LLN and were overdiagnosed. They had lower lung function, and more respiratory symptoms, self-reported asthma, eosinophils, and sleep apnea than other non-COPD participants . The main predictor of being overdiagnosed was overweight. Spirometry in participants reporting wheezing or cough and current smokers or participants with ≥20 tobacco pack-year history would have identified 85% of the undiagnosed cases.

Conclusion: Both over- and underdiagnosis of COPD is frequent. Undiagnosed individuals have better lung function and less symptoms, but similar prevalence of comorbidities and systemic inflammation. Overdiagnosed individuals have treatable traits including asthma, eosinophilic inflammation, and sleep apnea. The main predictor of being overdiagnosed was being overweight.