title: Methods of defining hypertension in electronic medical records: validation against national survey data.
abstract: Electronic medical records (EMR) can be a cost-effective source for hypertension surveillance. However, diagnosis of hypertension in EMR is commonly under-coded and warrants the needs to review blood pressure and antihypertensive drugs for hypertension case identification.
  
  
  
  We included all the patients actively registered in The Health Improvement Network (THIN) database, UK, on 31 December 2011. Three case definitions using diagnosis code, antihypertensive drug prescriptions and abnormal blood pressure, respectively, were used to identify hypertension patients. We compared the prevalence and treatment rate of hypertension in THIN with results from Health Survey for England (HSE) in 2011.
  
  
  
  Compared with prevalence reported by HSE (29.7%), the use of diagnosis code alone (14.0%) underestimated hypertension prevalence. The use of any of the definitions (38.4%) or combination of antihypertensive drug prescriptions and abnormal blood pressure (38.4%) had higher prevalence than HSE. The use of diagnosis code or two abnormal blood pressure records with a 2-year period (31.1%) had similar prevalence and treatment rate of hypertension with HSE.
  
  
  
  Different definitions should be used for different study purposes. The definition of 'diagnosis code or two abnormal blood pressure records with a 2-year period' could be used for hypertension surveillance in THIN.
authors.affiliation: Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada T2N 4Z6.
authors.forename: Mingkai
authors.initials: M
authors.lastname: Peng
authors.affiliation: Alberta Health Service, Calgary, AB, Canada T2N 2T9.
authors.forename: Guanmin
authors.initials: G
authors.lastname: Chen
authors.affiliation: Department of Medicine, University of Calgary, Calgary, AB, Canada T2N 4N1 Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada T2N 4N1.
authors.forename: Gilaad G
authors.initials: GG
authors.lastname: Kaplan
authors.affiliation: Department of Community Health Sciences, University of Manitoba, Winnipeg, MB, Canada R3E 0W3.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Lix
authors.affiliation: Department of Family Medicine, University of Alberta, Edmonton, AB, Canada T6G 2C8.
authors.forename: Neil
authors.initials: N
authors.lastname: Drummond
authors.affiliation: Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada T2N 4Z6.
authors.forename: Kelsey
authors.initials: K
authors.lastname: Lucyk
authors.affiliation: Department of Family Medicine, University of Calgary, Calgary, AB, Canada T2N 4N1.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Garies
authors.affiliation: Cumming School of Medicine, University of Calgary, Calgary, AB, Canada T2N 4N1.
authors.forename: Mark
authors.initials: M
authors.lastname: Lowerison
authors.affiliation: Departments of Clinical Neurosciences, University of Calgary, Calgary, AB, Canada T2N 4N1.
authors.forename: Samuel
authors.initials: S
authors.lastname: Weibe
authors.affiliation: Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada T2N 4Z6.
authors.forename: Hude
authors.initials: H
authors.lastname: Quan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000959:Antihypertensive Agents / Q000627:therapeutic use; D001794:Blood Pressure; D003430:Cross-Sectional Studies; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D057286:Electronic Health Records / Q000592:standards / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult
chemical_list: D000959:Antihypertensive Agents
keywords: antihypertensive drug; blood pressure; diagnosis code; electronic medical records; hypertension