Computer held chronic disease registers in general practice: a validation study.

Lists of patients receiving repeat prescriptions for epilepsy, diabetes, thyroid disease and asthma were compared with chronic disease registers stored on seven practice computers. Diabetes was the most accurately recorded disease: the names of 72% of patients receiving medication for this condition appeared on the relevant disease registers. Agreement between the two data sources was 68% for thyroid disease, 58% for asthma and 49% for epilepsy. The levels of accuracy are not yet high enough for the computerised chronic disease registers to provide an accurate estimate of the prevalence of these conditions, but new system developments suggest a more optimistic outlook for the future.