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223 "DEVELOPMENT OF AN ICD CODING DEFINITION FOR INFLAMMATORY BOWEL DISEASE" A Rezaie, H Quan, R Panaccione, B Li, RJ Hilsden INTRODUCTION: To facilitate the conduction of population-based epidemiologic studies, this study was performed to develop a valid indigenous criterion for capturing IBD patients through comprehensive and sophisticated administrative databases available in the province of Alberta.
Faculty of Medicine, University of Calgary, Calgary, Alberta
METHODS: Reports of endoscopy procedures performed within the Calgary Health Region (CHR) are housed in a computerized database (EndoPro). Computerized and manual search strategies were conducted on EndoPro database to categorize the patients undergone a colonoscopy within the period of 05/16/2000 through 04/01/2004 into definite IBD, possible IBD, and definite non-IBD patients (controls). The medical service history (ICD diagnostic codes) of the IBD patients and controls was tracked by a unique personal health identification number in physician claims, hospital abstracts and Ambulatory Care Classification System (ACCS) databases. ACCS is a made-in-Alberta database that collects information on facility-based ambulatory care (eg, Day surgeries and procedures). Between 1996-2004, ICD-9 and ICD-10 codes for Crohn's disease and ulcerative colitis were extracted. Over 100 administrative definitions were developed for IBD patients depending on the number and periodicity of IBD codes in each database. The most practical definition has been chosen to have a high specificity and an acceptable sensitivity.
RESULTS: 1,353 IBD patients and 15,506 definite non-IBD individuals were identified through EndoPro database search. The favourable definition classifies individuals as having IBD only if they have five physician claims or two ACCS claims or a hospitalization with an ICD diagnostic code of IBD. The definition must be met within a maximum time period of three years.
Administrative definition 2x2 table and test characteristics with 95% CI
EndoPro (Gold Standard) IBD
EndoPro (Gold Standard) Non-IBD
Sp=99.52% (99.40%-99.62%)
Administrative definition IBD
1115
74
Sn=82.40% (80.27%-84.40%)
Administrative definition Non-IBD
238
15432
PPV=93.78% (92.25%-95.08%)
NPV=98.48% (98.28%-98.67%)
CONCLUSION: Through a novel methodology, we have developed a reliable ICD coding definition for IBD which could be used in future population-based studies. Ongoing complementary chart reviews are being done on false-positive and false-negative cases to increase our specificity and sensitivity.