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THE EPIDEMIOLOGY OF INFLAMMATORY BOWEL DISEASE IN THE CALGARY HEALTH REGION; APPLICATION OF A NEW ADMINISTRATIVE DEFINITION
J Jones1, C Kenyon, S Devlin1, R Panaccione1, G Kaplan1, H Quan2
1Department of Medicine; 2Department of Community Health Sciences, Epidemiology and Biostatistics and Department of Surgery, University of Calgary, Alberta
BACKGROUND: As a result of delays to diagnosis as well as the relapsing, remitting and rare nature of inflammatory bowel disease (IBD) accurate incidence and prevalence estimates are difficult to obtain. Consequently, the utilization of large population-based data is imperative for estimating IBD occurrence and studying IBD-related outcomes.
OBJECTIVES: To estimate annual age and sex-adjusted, annual, prevalence and incidence rates of IBD in a large Canadian health region utilizing inpatient and outpatient administrative data.
METHODS: Utilizing a validated international disease classification (ICD) coding algorithm for defining IBD in administrative data (validated against endoscopic data), IBD cases were extracted from the inpatient (IP), physician claims (PC) and ambulatory care (ACCS) administrative databases between 1996 and 2002 in Calgary Health Region (CHR). Crude annual as well as age and sex-adjusted prevalence rates were calculated between 1996 through 2002. The mid year population from the CHR population registry was employed to define denominators.
RESULTS: After merging all three databases, case extraction yielded at total of 12, 068 true IBD cases in the CHR between 1996 and 2002. The annual age-adjusted prevalence rates rose slowly from 331 cases per 100,000 in 1996 (95% CI: 374 to 398) to 381 cases per 100,000 in 2002 (95% CI: 369 to 392). The crude IBD incidence rose slightly between 1999 (131 cases per 100,000 ; 95% CI: 124 to 138) and 2002 (142 cases per 100,000; 95% CI: 136 to 150). Age adjusted annual incidence rates were 143, 159, 142 and 152 cases per 100,000 for the years 1999, 2000, 2001 and 2002. Annual sex-adjusted prevalence rates were similar.
CONCLUSIONS: This newly validated administrative definition of IBD appears to yield prevalence estimates comparable to previously published Canadian prevalence data. Incidence estimates were significantly higher than those previously reported in the literature. The rising prevalence trend could be related to in-migration of individuals to the CHR, “urbanization” of IBD specific to the CHR or to a true rise in new cases.