A Single-Center Observational Study on the Impact of Symptom Assessment Timing on the Short-Term Efficacy of 5-ASA Therapy in Patients With Initial-Onset or Relapsed Mild-to-Moderate Active Ulcerative Colitis

The symptom improvement at 12-week after enrollment

This outcome measure is symptom improvement at 12 weeks after enrollment, assessed by the change in modified Mayo score from baseline. This score evaluates key ulcerative colitis symptoms, including stool frequency, rectal bleeding, and urgency, with higher scores indicating greater severity. Participants are adults with newly diagnosed or relapsing mild-to-moderate UC receiving mesalazine therapy. Symptom severity is recorded at baseline and at week 12, and improvement is defined as a reduction in the total modified Mayo score, reflecting clinical response to treatment during the 12-week period.

Time frame: 12-week after enrollment

The symptom remission at 12-week after enrollment

This outcome measures the symptom remission at 12 weeks post-enrollment in the study population of adult UC patients treated with mesalazine therapy. Eligible participants are those meeting the 2023 Chinese Consensus diagnostic criteria for newly diagnosed or mild-to-moderate active ulcerative colitis (baseline modified Mayo score 3-10), with no recent use of corticosteroids, immunosuppressants, biologics, or anti-diarrheal medications, and without serious comorbidities, concurrent trial participation, or pregnancy. Symptom remission is defined as normal stool frequency and no rectal bleeding or urgency, at the 12-week follow-up visit. This stringent definition indicates minimal disease activity across all symptom domains and is used to evaluate the efficacy of mesalazine in inducing clinical remission by the 12-week mark.

Time frame: 12-week after enrollment

The clinical improvement at 12-week after enrollment

This outcome measures the proportion of patients achieving clinical improvement at the 12-week follow-up after enrollment. Clinical improvement is defined as a marked reduction in ulcerative colitis disease activity from baseline. Specifically, a patient must exhibit a decrease in the total modified Mayo score by at least 3 points and at least 30% relative to their baseline score, indicating a significant overall improvement in symptoms. In addition, there must be an improvement in rectal bleeding, evidenced by a decrease of at least 1 point in the rectal bleeding subscore. All participants will be assessed at week 12 post-enrollment to determine if they meet these criteria, reflecting meaningful clinical improvement after 12 weeks of mesalazine therapy.

Time frame: 12-week after enrollment

The clinical remission at 12-week after enrollment

Clinical remission at 12 weeks after enrollment is a key secondary outcome measure, defined as achieving a total modified Mayo score of ≤2 with no individual subscore greater than 1 at the 12-week follow-up. This outcome evaluates the effectiveness of 12-week mesalazine therapy (oral or oral-plus-topical) in inducing remission in adult ulcerative colitis patients. Participants are aged 18-59 years and meet the 2023 Chinese Consensus diagnostic criteria for newly diagnosed or mild-to-moderate active UC, with a baseline modified Mayo score between 3 and 10. Patients with recent use of corticosteroids, immunosuppressants, biologic therapies, or anti-diarrheal medications, as well as those in other clinical trials or with serious comorbidities or pregnancy, are excluded. The proportion of patients meeting the clinical remission criteria at week 12 will be determined, providing a clear measure of therapeutic success in this population.

Time frame: 12-week after enrollment