Factors associated with misdiagnosis of COPD in primary care

Aim: To assess the misclassification of chronic obstructive pulmonary disease (COPD) in Australian primary care. Methods: A cross-sectional study was performed in 31 (19%) practices in one Australian state. 341 patients with COPD (database diagnosis or current use of tiotropium plus GP confirmation) completed spirometry and questionnaires. Predictors of misclassification were investigated with multi-level mixed-effects logistic regression allowing for clustering by practice. Results: Spirometric confirmation of COPD (forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) ratio <0.7) was not present in 107 (31%) patients; 60 (56%) had normal lung function, seven (7%) had scalloped flow-volume curves and FEV1 <80% predicted, 40 (37%) had restriction (FVC <80% predicted). Among 107 misclassified patients the bronchodilators used were tiotropium in 26% and long-acting beta(2)-agonists in 22%. The likelihood of misclassification increased with overweight/obesity (odds ratio (OR) 2.66; 95% CI 1.50 to 4.70) and self-reported allergic rhinitis/hay fever (OR 1.72; 95% CI 1.13 to 2.64) after adjustment for age, gender, and smoking. Conclusions: Symptom-based diagnosis of COPD in primary care is unreliable, especially if patients are overweight, so diagnostic spirometry is essential to avoid inappropriate management. (C) 2011 Primary Care Respiratory Society UK. All rights reserved. JA Walters et al. Prim Care Respir J 2011; 20(4): 396-402 http://dx.doi.org/10.4104/pcrj.2011.00039