Chronic obstructive pulmonary disease prevalence estimated using a standard algorithm based on electronic health data in various areas of Italy

Aim: to estimate the prevalence of chronic obstructive pulmonary disease (COPD) by integrating various administrative health information systems. Methods: prevalent COPD cases were defined as those reported in the hospital discharge registry (HDR) and cause of mortality registry (CMR) with codes 490*, 491 492, 494* e 496* of the International diseases classification 9th revision. Annual prevalence was estimated in 35+ year-old residents in six Italian areas of different sizes, in the period 2002-2004. We in-eluded cases observed In the previous four years who were alive at the beginning of each year. Results: in 2003, age-standardized prevalence rates varied from 1.6% in Venice to 5% in Taranto. Prevalence was higher in males and increased with age. The highest rates were observed in central (Rome) and southern (Taranto) cities, especially in the 35-64 age group. HDR contributed 91% of cases. Health-tax exemption registry would increase the prevalence estimate by 0.2% if used as a third data source. Conclusions: with respect to the National Health Status survey, COPD prevalence is underestimated by 1%-3%; this can partly be due to the selection of severe and exacerbated COPD by the algorithm used. However, age, gender and geographical characteristics of prevalent cases were comparable to national estimates. Including cases observed in previous years (longitudinal estimates) increased the point estimate (yearly) of prevalence two or three times in each area.