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(Hypertension. 2009;54:1423.)
© 2009 American Heart Association, Inc.

Original Articles

Validation of a Case Definition to Define Hypertension Using Administrative Data

Hude Quan; Nadia Khan; Brenda R. Hemmelgarn; Karen Tu; Guanmin Chen; Norm Campbell; Michael D. Hill; William A. Ghali; Finlay A. McAlister for the Hypertension Outcome and Surveillance Team of the Canadian Hypertension Education Programs

From the Departments of Community Health Sciences (H.Q., B.R.H., G.C., N.C., M.D.H., W.A.G.) and Medicine (B.R.H., N.C., M.D.H., W.A.G.), University of Calgary, Calgary, Alberta, Canada; Department of Medicine (N.K.), University of British Columbia, Vancouver, British Columbia, Canada; Institute for Clinical Evaluative Sciences (K.T.), Toronto, Ontario, Canada; Department of Family and Community Medicine (K.T.), University of Toronto, Toronto, Ontario, Canada; Department of Medicine (F.A.M.), University of Alberta, Edmonton, Alberta, Canada.

Correspondence to Hude Quan, Department of Community Health Sciences, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada. E-mail hquan{at}ucalgary.ca

We validated the accuracy of case definitions for hypertension derived from administrative data across time periods (year 2001 versus 2004) and geographic regions using physician charts. Physician charts were randomly selected in rural and urban areas from Alberta and British Columbia, Canada, during years 2001 and 2004. Physician charts were linked with administrative data through unique personal health number. We reviewed charts of 50 randomly selected patients >35 years of age from each clinic within 48 urban and 16 rural family physician clinics to identify physician diagnoses of hypertension during the years 2001 and 2004. The validity indices were estimated for diagnosed hypertension using 3 years of administrative data for the 8 case-definition combinations. Of the 3362 patient charts reviewed, the prevalence of hypertension ranged from 18.8% to 33.3%, depending on the year and region studied. The administrative data hypertension definition of "2 claims within 2 years or 1 hospitalization" had the highest validity relative to the other definitions evaluated (sensitivity 75%, specificity 94%, positive predictive value 81%, negative predictive value 92%, and 0.71). After adjustment for age, sex, and comorbid conditions, the sensitivities between regions, years, and provinces were not significantly different, but the positive predictive value varied slightly across geographic regions. These results provide evidence that administrative data can be used as a relatively valid source of data to define cases of hypertension for surveillance and research purposes.

Key Words: hypertension • surveillance • International Disease Classification • health information • administrative data

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