Quantifying concomitant diagnosis of asthma and COPD in UK primary care

Background: Asthma and COPD share many characteristics and symptoms, and the differential diagnosis between the two diseases can be difficult in primary care. This study explores potential overlap between both diseases in a primary care environment. Aim: This study aims to quantify how commonly patients with COPD have a concomitant diagnosis of asthma, and how commonly patients with asthma have a concomitant diagnosis of COPD in UK primary care. Design and Setting: 400 COPD patients and 352 asthma patients were identified from the Clinical Practice Research Datalink (CPRD) in separate validation studies and the diseases were confirmed by review of GP questionnaires. Method: The prevalence of concurrent asthma and COPD in validated cases of either disease were examined based on CPRD coding, GP questionnaires and requested additional information. We also aimed to determine the extent of possible misdiagnosis and missed opportunities for diagnosis. Results: More than half (52.5%) of validated COPD patients had ever received a diagnostic asthma Read code. However, when considering additional evidence to support a diagnosis of asthma, concurrent asthma was only likely in 14.5% (95% CI: 11.2%; 18.3%) of validated COPD patients. Of the validated asthma patients, 15.1% have ever received a diagnostic COPD Read code, although COPD was only likely in 14.8% (95% CI: 11.3%; 19.0%) of validated asthma patients. Conclusion: A concurrent asthma and COPD diagnosis appears to affect a relative minority of patients with COPD (14.5%) or asthma (14.8%). Asthma diagnosis may be over recorded in people with COPD