Increasing use is being made of routinely collected electronic patient data in health services research. The aim ofthe present study was to valuate the potential usefulness of a comprehensive database used routinely in the public healthcaresystem in Hong Kong, using antihypertensive drug prescriptions in primary care as an example.
Data on antihypertensive drug prescriptions were retrieved from the electronic Clinical Management System (e-CMS) of all primary are clinics run by the Health Authority (HA) in the New Territory East (NTE) cluster of Hong Kongbetween January 2004 and June 2007. Information was also retrieved on patients' demographic and socioeconomiccharacteristics, visit type (new or follow-up), and relevant diseases (International Classification of Primary Care, ICPC codes).
1,096,282 visit episodes were accessed, representing 93,450 patients. Patients' demographic and socio-economicdetails were recorded in all cases. Prescription details for anti-hypertensive drugs were missing in only 18 patients (0.02%).However, ICPC-code was missing for 36,409 patients (39%). significant independent predictors of whether disease codes wereapplied included patient age . 70 years (OR 2.18), female gender (OR 1.20), district of residence (range of ORs in more ruraldistricts; 0.32.0.41), type of clinic (OR in Family Medicine Specialist Clinics; 1.45) and type of visit (OR follow-up visit; 2.39).In the 57,041 patients with an CPC-code, in complicated hypertension (ICPC K86) was recorded in 45,859 patients (82.1%).The characteristics of these patients were very similar to those of the non-coded group, suggesting that most non-coded patientson antihypertensive drugs are likely to have uncomplicated hypertension.
The e-CMS database of the HA in Hong Kong varies in quality in terms of recorded information. Potential futurehealth services research using demographic and prescription information is highly feasible ut for disease-specific researchdependant on ICPC codes some caution is warranted. In the case of uncomplicated hypertension, future research on pharmacoepidemiology(such prescription patterns) and clinical issues (such as side-effects of medications on metabolic parameters)seems feasible given the large size of the data set and the comparability of oded and non-coded patients.
The use of electronic patient records within healthcare systemshas important implications for health servicesresearch. When used within a comprehensive computerizeddata management system such records can supportresearch into the aetiology of disease1,2, the predictivevalue of symptoms in diagnosis3, the clinical effectivenessand cost effectiveness of interventions4, and inevaluating whole-system approaches to the organizationand delivery of care5.