title: Health services research in the public healthcare system in Hong Kong: an analysis of over 1 million antihypertensive prescriptions between 2004-2007 as an example of the potential and pitfalls of using routinely collected electronic patient data.
abstract: BACKGROUND
  Increasing use is being made of routinely collected electronic patient data in health services research. The aim of the present study was to evaluate the potential usefulness of a comprehensive database used routinely in the public healthcare system in Hong Kong, using antihypertensive drug prescriptions in primary care as an example.
  
  
  METHODS
  Data on antihypertensive drug prescriptions were retrieved from the electronic Clinical Management System (e-CMS) of all primary care clinics run by the Health Authority (HA) in the New Territory East (NTE) cluster of Hong Kong between January 2004 and June 2007. Information was also retrieved on patients' demographic and socioeconomic characteristics, visit type (new or follow-up), and relevant diseases (International Classification of Primary Care, ICPC codes).
  
  
  RESULTS
  1,096,282 visit episodes were accessed, representing 93,450 patients. Patients' demographic and socio-economic details 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 were applied included patient age > or = 70 years (OR 2.18), female gender (OR 1.20), district of residence (range of ORs in more rural districts; 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 ICPC-code, uncomplicated 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 patients on antihypertensive drugs are likely to have uncomplicated hypertension.
  
  
  CONCLUSIONS
  The e-CMS database of the HA in Hong Kong varies in quality in terms of recorded information. Potential future health services research using demographic and prescription information is highly feasible but for disease-specific research dependant on ICPC codes some caution is warranted. In the case of uncomplicated hypertension, future research on pharmaco-epidemiology (such as 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 coded and non-coded patients.
authors.affiliation: General Practice and Primary Care, Division of Community-Based Sciences, Faculty of Medicine, University of Glasgow, 1 Horselethill Road, Glasgow G12 9LX, UK. wong_martin@cuhk.edu.hk
authors.forename: Martin C S
authors.initials: MC
authors.lastname: Wong
authors.forename: Johnny Y
authors.initials: JY
authors.lastname: Jiang
authors.forename: Jin-ling
authors.initials: JL
authors.lastname: Tang
authors.forename: Augustine
authors.initials: A
authors.lastname: Lam
authors.forename: Hong
authors.initials: H
authors.lastname: Fung
authors.forename: Stewart W
authors.initials: SW
authors.lastname: Mercer
mesh_terms: D000368:Aged; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D016000:Cluster Analysis; D016208:Databases, Factual; D004363:Drug Utilization / Q000706:statistics & numerical data*; D005260:Female; D005568:Forms and Records Control; D006302:Health Services Research; D006723:Hong Kong; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D038801:International Classification of Diseases; D008297:Male; D016347:Medical Records Systems, Computerized / Q000706:statistics & numerical data*; D008875:Middle Aged; D011320:Primary Health Care / Q000145:classification; D011634:Public Health; D012959:Socioeconomic Factors
chemical_list: D000959:Antihypertensive Agents