Introduction To determine if using a combination of hospital administrative data and ambulatory care physician billings can accurately identify patients with congestive heart failure (CHF), we tested 9 algorithms for identifying individuals with CHF from administrative data. Methods The validation cohort against which the 9 algorithms were tested combined data from a random sample of adult patients from EMRALD, an electronic medical record database of primary care physicians in Ontario, Canada, and data collected in 2004/05 from a random sample of primary care patients for a study of hypertension. Algorithms were evaluated on sensitivity, specificity, positive predictive value, area under the curve on the ROC graph and the combination of likelihood ratio positive and negative. Results We found that that one hospital record or one physician billing followed by a second record from either source within one year had the best result, with a sensitivity of 84.8% and a specificity of 97.0%. Conclusion Population prevalence of CHF can be accurately measured using combined administrative data from hospitalization and ambulatory care.

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Beta-blockers are less beneficial than other antihypertensive drugs in the elderly with hypertension. All elderly patients in Ontario, Canada (population over 3.5 million elderly) without co-morbidities who were first treated for hypertension with a beta-blocker were studied in a retrospective population-based cohort study (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002) to determine the characteristics of those prescribed beta-blockers. Of the 194 761 patients in our cohort, 25 485 (13%) were prescribed a betablocker as their first antihypertensive agent. On multivariate analysis, factors significantly associated with being prescribed a beta-blocker as first-line therapy included male sex (adjusted odds ratio (