Prevalence estimates for chronic diseases in Italy: exploring the differences between self-report and primary care databases.

Background: The aim of this study was to describe population and primary care morbidity and to examine how the differences vary across the diseases and are influenced by patients' demographic characteristics.

Methods: A comparison of the prevalence of four chronic conditions for 432747 patients from the Health Search Database (HSD) and 119799 individuals from a Health Interview Survey was carried out. A linear regression was performed to study the associations between age and difference in morbidity.

Results: Similar prevalence was found for diabetes and hypertension, whereas for chronic obstructive pulmonary disease (COPD) and gastroduodenal ulcer lower HSD prevalence was reported. Among females, age was always associated with morbidity difference. Among males, significant associations were found only for COPD (R2 = 0.81; p = 0.001) and gastroduodenal ulcer (R2 = 0.93; p < 0.001).

Conclusions: The difference between population and primary care morbidity is affected by disease under investigation and patients' demographic characteristics. Therefore, in choosing the more cost-effective approach to collect data such evidence should be taken into account, and results should be interpreted with great caution.