Perianal Fistula (PAF) Validation and Burden of Illness Study

The purpose of this study is to gain a better understanding of the disease burden and unmet need of perianal fistulas within Crohn's disease (CD) in Ontario.

This is a retrospective follow-up observational study of participants with CD with and without complex perianal fistula (CPAF) from January 2002 to March 2017. The study will verify the potential of using procedure codes to reliably identify participants with CPAF in Validation Study (Objective 1), compare Crohn's participants with CPAF (cases) to matched participants without CPAF (controls) to determine the disease burden and healthcare resource utilization of Crohn's related CPAF in Ontario, and will describe the participant's journey among Crohn's participants following the first diagnosis of CPAF (Objective 3).

The study will enroll approximately 600 participants (300 participants with CPAF and 300 participants without CPAF). All participants will be enrolled in 2 observation groups:

* CD Participants with/without CPAF (ICES data)
* CD Participants with CPAF - The Ottawa Hospital (TOH)

The data will be collected through Ontario health administrative data. Participants will be observed retrospectively who were diagnosed with CD with and without fistula between index period: April 2002 and July 2013. Participants will be followed up retrospectively from the index period (that is onset of CPAF) to the end of study (Objective 2), and for 5 years following the (Objective 3) index date defined as onset of CPAF will be selected based on the first time they meet the first code in the case definition identified in Objective 1 between April 1, 2005 to March 31, 2012. The overall time for data collection in this study will be approximately 7 months.

Eligibility Criteria:
Inclusion Criteria for Objective 1:

1. Inclusion in the TOH "reference" database.
2. Aged 18-105 inclusive at date of index.
3. Participant can be linked between TOH "reference" database to the Institute for Clinical Evaluative Sciences (ICES) databases based on health card number.
4. Incident inclusion in the Ontario Crohn's and Colitis Cohort (OCCC) between April 1, 2002 to July 1, 2013.
5. Incident diagnosis of CPAF in TOH database between April 1, 2004 to July 1, 2015.

Inclusion Criteria for Objective 2:

1. Participants were incident in the OCCC from April 1, 2002 to March 31, 2012.
2. The case meets the PAF case definition identified in Objective 1 in the selection period (April 1, 2005 to March 31, 2012).
3. Aged 18-105 inclusive at date of index.

Inclusion Criteria for Objective 3:

1. Inclusion in the OCCC at or prior to index visit with a diagnosis of Crohn's disease.
2. The case meets the CPAF case definition identified in Objective 1 in the selection period.
3. Have to have 5 years of follow-up.
4. Aged 18-105 inclusive at date of index.

Exclusion Criteria for Objective 1:

1. Missing demographics at index date (sex, age, Local Health Integration Network (LHIN), income quintile) in all databases.
2. Death date in the ICES data prior to TOH CPAF incidence date.

Exclusion Criteria for Objective 2:

1. Missing demographics at index date (sex, age, neighbourhood income quintile, LHIN).
2. Death during 5-year analysis period.
3. Ontario Health Insurance Plan (OHIP) coverage is terminated during the follow-up example if the participant moves to another province.
4. Meeting the case definition during the lookback period.
5. Cases for whom a matched control cannot be found.

Exclusion Criteria for Objective 3:

1. Missing demographics at index date (sex, age, neighbourhood income quintile, LHIN).
2. Death during 5-year analysis period.
3. OHIP coverage is terminated during the 5-year analysis period example if the participant moves to another province.
4. Meeting the case definition during the lookback period.