The prevalence of ulcerative colitis (UC), which is one of the inflammatory bowel diseases, is known to be increasing and the majority of patients (≥ 85%) have experienced mild or moderate severity.

5-Aminosalicylic acid (5-ASA), immunomodulator, or biologics, etc are prescribed to treat UC, however 5-ASA is generally considered the first-line therapy. The recent UC treatment guideline in Korea and the United States/ European Union (US/EU) have recommended higher daily dose for patients with mild or moderate severity than the previous guidelines since 2017. Accordingly, it is assumed that the average daily treatment dose of 5-ASA would increase in patients who were initially diagnosed with UC in real-world clinical practice in Korea. However, there are not many studies evaluating the treatment patterns and health outcomes of 5-ASA based on the recent treatment guideline in South Korea.

This study, hence, aims to investigate the impact of changes in daily dose of 5-ASA on the treatment patterns and health outcomes such as recurrence rate, hospitalization rate, and surgery rate in real world practice using Health Insurance Review and Assessment (HIRA) claims database.

Inclusion Criteria:

• Patients who were diagnosed with UC during the index period.

• Patients who had at least two claims of 5-ASA (sulfasalazine, balsalazide, mesalamine) during the index period.

• Patients who underwent at least one endoscopy within a 3-month period prior to the index date (i.e. the first date of diagnosis with UC).

  • Defined as a claim with relevant endoscopy procedure code.
  • Include the upper gastrointestinal endoscopy, colonoscopy, sigmoidoscopy, which are identified using the procedure code.

• Patients who were treated with 5-ASA continuously for at least 1-month after the index date.

  • Defined as those who were treated with 5-ASA for more than 30 days within 6-month after the index date (i.e. the first date of diagnosis with UC).

Exclusion Criteria:

• Patients less than 15 years old as of the index date (<15 years old).

• Patients who were treated with 5-ASA during the baseline period (i.e. 12-month prior to the index date).

• Patients who were diagnosed with UC during the baseline period.

• Patients who received steroids, immunosuppressants, or biologics during the baseline period.

  • Steroid includes both oral medication and intravenous (IV) injection. The analysis will include the moderate- to high-dose of cumulative steroid use, which is defined as >=30mg of prednisolone, >= 50mg of methylprednisolone, or >=50mg of hydrocortisone.
  • Immunosuppressants is defined as at least one claim with Azathioprine or 6-Mercaptopurine.
  • Biologics is defined as at least one claim with Infliximab, Adalimumab, Ustekinumab, Vedolizumab, Golimumab, or Tofacitinib.

• Patients who were diagnosed with Crohn's disease at any time in the overall study period.

  • Defined as a claim with relevant Crohn's disease code recorded as primary diagnosis during the baseline period or follow-up period (i.e. entire study period).

Patients will be selected from Korean HIRA claim database according to the inclusion/exclusion criteria. The Korean patients who were initially diagnosed with UC from 01 January 2009 to 30 June 2018 will be included in this study.