Background: Studies have suggested that chronic obstructive pulmonary disease (COPD) is commonly misdiagnosed and misclassified in primary care, but less is known about the quality of diagnosis in specialist respiratory care.
Aims: To measure the accuracy of COPD diagnosis and classification of airway obstruction in primary care and at a specialist respiratory centre, and to explore associations between misdiagnosis and misclassification and a range of explanatory factors.
Methods: Data were obtained for 1,205 referrals to a specialist respiratory centre between 2007 and 2010. Standard analysis methods were used.
Results: The majority of patients were referred for pulmonary rehabilitation (676/1,205, 56%). Of 1,044 patients with a primary care diagnosis of COPD, 211 (20%) had spirometry inconsistent with COPD. In comparison, of 993 specialist centre diagnoses, 65 (6.5%) had inconsistent spirometry. There was poor agreement between the airflow obstruction grade recorded on the referral and that based on spirometry (kappa=0.26, n=448), whereas agreement between the respiratory centre assessment of airflow obstruction and spirometry was good (kappa=0.88, n=1,016). Referral by practice nurse was associated with accuracy of airflow obstruction classification in primary care (OR 1.85, 95% CI 1.33 to 2.57). Males were more likely than females to have an accurate specialist care classification of airway obstruction (OR 1.40, 95% CI 1.01 to 1.93). Grade of airway obstruction changed between referral and assessment in 56% of cases.
Conclusions: In primary care, a proportion of patients diagnosed with COPD do not have COPD, and misclassification of grade of airflow obstruction is common. Misdiagnosis and misclassification is less common in the specialist care setting of BreathingSpace.