Diagnosis of airway obstruction in primary care in the UK: the CADRE (COPD and Asthma Diagnostic/management REassessment) programme 1997-2001

OBJECTIVE: Asthma and COPD require different management strategies, but differentiation in primary care is difficult. This primary care support initiative observed the impact of spirometry and clinical assessment on the diagnosis of airway disease. MATERIALS AND METHODS: Of 61,191 patients aged > or =40 years being treated for respiratory conditions within 1003 UK primary care practices, 43,203 underwent a diagnostic review including standardized spirometric assessment. The proportion of patients in whom the diagnosis was changed by the additional information was determined. The relationship of various patient characteristics was compared with the baseline and review diagnoses and with any change in diagnosis. RESULTS: Asthma was initially diagnosed in 43% of patients, COPD in 35%, mixed disease in 9%, and other respiratory condition in 13%. Patients initially diagnosed with asthma, mixed disease, or another condition were more likely to have their diagnosis changed at review (54%, 46%, and 63%, respectively) than those initially diagnosed with COPD (14%). A change from asthma to COPD was associated with male gender, smoking, older age, and reduced lung function, the opposite being associated with a change from COPD to asthma. CONCLUSION: In this study, a clinical review supplemented by additional information including spirometry highlights apparent mislabeling of significant numbers of patients with chronic obstructive disease in general practice with significant implications for individual treatment and healthcare provision. This study shows that the addition of more clinical information can have a major effect on diagnostic tendency in patients with airway disease. An initial diagnosis of COPD seems less likely to change following review than an asthma diagnosis. While it is likely that greater information leads to a more accurate diagnosis, the differential effect of new information on diagnostic labeling highlights the insecurity of the diagnostic process in primary care in the UK.