Finding the missing millions – the impact of a locally enhanced service for COPD on current and projected rates of diagnosis: a population-based prevalence study using interrupted time series analysis

BACKGROUND: Many patients with chronic obstructive pulmonary disease (COPD) are not identified until their condition is relatively advanced and there is a considerable gap between the modelled and diagnosed prevalence of the disease. We have previously shown that, in the first year after the introduction of a locally enhanced service (LES) for COPD in 2008, there was a significant step-up in the diagnosed prevalence. AIMS: To investigate whether this initial increase in prevalence was sustained, and the impact of this increase on future projected rates of COPD diagnosis. METHODS: Using data from 2005–2011, we compared the prevalence of diagnosed COPD in the LES Primary Care Trust (LES-PCT) before and after it was introduced. Data were compared with a neighbouring PCT, the London Strategic Health Authority, and England. The true prevalence of COPD was estimated based on data from the Health Survey for England. Trends were extrapolated to estimate the proportion of patients that would be diagnosed in 2017. RESULTS: The introduction of the LES was associated with a significant acceleration in the annual increase in diagnosed COPD (p<0.0001). By 2011 the prevalence was 1.17% in the LES-PCT compared with a predicted value of 0.91% (95% CI 0.86% to 0.95%) based on the pre-LES trend. There was no change in the rate of increase in COPD prevalence for the neighbouring PCT or for London as a whole. The LES-PCT would be expected to diagnose 55.6% of COPD patients by 2017 compared with only 27.3% without the LES, and only 33.3% would be diagnosed in the neighbouring PCT. CONCLUSIONS: These data suggest that, with appropriate incentives, it is possible to achieve a sustained improvement in COPD case-finding in primary care and that such policies need to be implemented systematically.