Estimate of the prevalence of subjects with chronic diseases in a province of Northern Italy: a retrospective study based on administrative databases.

Despite the difficulty of having a unique definition of chronic disease, the prevalence obtained was coherent with the estimates reported by other national surveillance systems such as Passi and Passi d'Argento. Underestimates were observed when international comparisons were done; however, when we used less stringent definitions of chronic diseases, similar results were obtained.