Table 1.
Definitions of outcomes (utilization of specialist gastroenterology care, health services utilization, surgery and medication utilization) and selected covariates
| Outcome | Definition | |
|---|---|---|
| Utilization of specialist gastroenterology care | 1. Having ever seen a gastroenterologist within 1 year of IBD diagnosis 2. Having a gastroenterologist as the primary provider of IBD-specific care (i.e., the majority of IBD-specific outpatient visits were to a gastroenterologist). | Gastroenterologist: Board-certified gastroenterologist or general internists who performed more than 50 endoscopies per year (11,30,31). Physicians without sufficient endoscopy codes in a single year but had sufficient endoscopy codes either in the year prior or the year after were also considered gastroenterologists. IBD-specific outpatient visits: Outpatient visits with an OHIP code for either CD (555) or UC (556) |
| Health services utilization | 1. IBD-related hospitalization in the month before or after IBD diagnosis 2. IBD-related ED visit in the month before or after IBD diagnosis 3. IBD-specific hospitalization within 1 and 5 years of IBD diagnosis (excluding the first month following IBD diagnosis) 4. IBD-specific ED visit within 1 and 5 years of IBD diagnosis (excluding the first month following IBD diagnosis) | IBD-specific ED visit or hospitalization: ED visit or hospitalization with a most responsible diagnosis of CD (ICD-9: 555; ICD-10: K50) or UC (ICD-9: 556; ICD-10: K51) IBD-related ED visit or hospitalization: IBD-specific hospitalization or ED visit; hospitalization or ED visit with a most responsible diagnosis of any sign, symptom or extra-intestinal manifestation of IBD (Supplementary Table S1) |
| Surgery | 1. Intestinal resection within 1 and 5 years of IBD diagnosis (CD only) 2. Colectomy within 1 and 5 years of IBD diagnosis (UC only) | See Supplementary Table S2 for a previously validated list of procedure codes (28,32) |
| Utilization of IBD medications | 1. ≥1 prescription for an immunomodulator within 1 and 5 years of IBD diagnosis 2. ≥1 prescription for a biologic within 1 and 5 years of IBD diagnosis 3. ≥1 prescription for systemic corticosteroids within 1 and 5 years of IBD diagnosis | Immunomodulator: Azathioprine, 6-mercaptopurine, methotrexate, cyclosporin or tacrolimus Biologic: Infliximab, adalimumab, certolizumab, golimumab, ustekinumab, vedolizumab or natalizumab See Supplementary Table S3 for a list of DINs associated with immunomodulators, biologics and systemic corticosteroids |
| Opioid use | 1. Chronic opioid use within 1 and 5 years of IBD diagnosis | ≥1 opioid prescription at least 91 days after the first opioid prescription, with no interval ≥120 days between successive opioid prescriptions (33) |
| Covariate | Definition | |
| Comorbidities | 1. Tertile of comorbidity score | Johns Hopkins ACG System Version 10 |
| Time to IBD Diagnosis | 1. Time from first diagnostic code deemed to be ‘most likely IBD’ to the first IBD diagnostic code, categorized as <1 month, 1 month to <6 months, 6 months to <12 months, and ≥12 months | Most likely IBD: Codes identified in a survey of gastroenterologists in which they were asked to rank potential codes as being indicative of a future diagnosis of IBD (12). Those with a mean score ≥4 on a 5-point Likert scale were included in the list of most likely IBD codes. Codes include signs, symptoms and common extra-intestinal manifestations of IBD (Supplementary Table S5). |
CD, Crohn’s disease; DIN, drug identification number; ED, emergency department; IBD, inflammatory bowel disease; ICD, International Classification of Diseases; OHIP, Ontario Health Insurance Plan; UC, ulcerative colitis.