Epidemiological usefulness of population-based electronic clinical records in primary care: estimation of the prevalence of chronic diseases

Objective. To estimate the prevalence of selected chronic illnesses based on electronic clinical records in primary care (ECRPC) and to assess its usefulness for epidemiological research, by comparing ECRPC data against those reported by a contemporary health survey. Methods. Design: Descriptive cross-sectional study. Setting: All primary care medical consultations in the Madrid Regional Public Health System (PHS). Subjects: A total of 23 535 182 ECRPC-registered episodes of illness, generated by PHS patients over 15 years of age seeking medical care during 2005-06. Main outcome measures: Prevalences of chronic diseases estimated on the basis of medically examined cases registered in ECRPC and morbidity as reported by a contemporary health survey covering the same geographic area. Results. A total of 52.5% of the adult population had some chronic health problem. The highest overall prevalences were hypertension (14.8%), mental disorders (12.0%) and allergy (11.6%). Prevalences were generally highest among women, elderly and the native population. Depending on the specific disease, ECRPC-based prevalences were similar to (e.g. diabetes), higher (e.g. chronic skin problems) or lower (e.g. asthma and dyslipidaemia) than those reported by surveys, with certain age- and sex-related variations. Conclusions. Prevalences estimated from ECRPC and survey data present variations depending on the disease, age and sex. Both data sources provide complementary information about chronic disease prevalence. ECRPC have the advantage of generating an ongoing standardized register and entailing no additional effort for health professionals.