Methodology for Assessing the Usefulness of General Practice Data for Research in One Research Network

The purpose of the study was to test the completeness and accuracy of data from general practice clinical computer systems for research. A cross-sectional survey was used to measure: (1) accuracy and completeness of diagnostic data; (2) completeness and timeliness of clinical measurements; and (3) completeness of risk factor data. High levels of completeness were found for recorded blood pressure (over 80 per cent) and for body mass index (75 per cent), which differed between population groups. Depending on the case definition used, a sevenfold variation was found in the prevalence of depression; fivefold for peptic ulcer disease; threefold for hyperlipidaemia; and very little for hypothyroidism. These results illustrate how routine clinical data in selected high recording practices are now achieving reasonable levels of accuracy and completeness for a range of key variables, although there is substantial inter-practice variation. The data quality opens exciting possibilities for study design.