Population and health services research can be performed by linkage analysis of administrative data. However, the robustness of study results is determined by the accuracy of the diagnostic coding.
To estimate the awareness, use and accuracy of the International Classification of Diseases, Ninth Revision (ICD-9) coding by physicians providing services for patients with Crohn's disease (CD) and ulcerative colitis (UC).
All Ontario gastroenterologists and a 10% random sample of internists, pediatricians, pediatric or general surgeons, and family physicians were surveyed by postal questionnaire to estimate the frequency and 95% CI of using codes 555 or 556 when billing for CD- and UC-related services, respectively. c2 tests were used for between-group comparisons.
Of the physicians who were surveyed, 67.7% (416 of 614) responded; 258 of 391 (66%) who were still practising in Ontario saw patients with inflammatory bowel disease (IBD), and 54% had more than 10 IBD patients; 86.5% (95% CI 82.4% to 90.6%) were familiar with ICD-9 codes, and 91.4% (95% CI 88.1% to 95.6%) used the codes 555 (CD) or 556 (UC) for billing. Rates of ICD-9 use did not differ by sex but were used more frequently by those graduating after 1981 (P