The Fecal Immunoassay Occult Blood Test Combined With Calprotectin Sequential Linkage Imaging Endoscopy Screening Strategy for Monitoring Tumor Changes Associated With Long-duration Ulcerative Colitis (DETECT-UCAN)

Long-standing Ulcerative Colitis High-risk Cohort

Participants with long-standing UC meeting high-risk criteria (disease duration >8/10 years, PSC, family history, or prior neoplasia). All participants undergo a unified surveillance protocol: baseline data collection → fecal sample collection for FIT and FC testing → LCI colonoscopy within 4 weeks regardless of stool test results.

Diagnostic Performance of Combined FIT+FC for UCAN

Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) of combined FIT+FC testing (either positive defined as positive) for detecting UCAN, using LCI colonoscopy with histopathology as the reference standard.

UCAN Detection Rate

Proportion of patients with pathologically confirmed UCAN (LGD, HGD, or CRC) among all patients who complete LCI colonoscopy

Comprehensive completion rate of the joint screening process

Unit of measurement: Percentage (%) Detailed description

To evaluate the overall implementation quality of the "FIT+FC sequential LCI" screening strategy, this indicator was set as a composite endpoint. Summary rule (mathematical definition) : Subjects who simultaneously meet all of the following five conditions are defined as "fully compliant process participants" :

• Fecal sample collection was successful;

  • The sample quality is qualified;

    • Both the FIT and FC laboratory tests have been completed. ④ Complete the LCI colonoscopy within 4 weeks; ⑤ The Boston Quality of Bowel Preparation Scale (BBPS) score is ≥ 6 points. The reported value of this result measurement item = (the number of fully compliant process participants/the total number of participants in the group) × 100%.

(Note: The completion rates of each individual link will be presented as baseline characteristics or descriptive data in the attached materials, and will not be separately used as result measurement items for

Patient Adherence

Proportion of patients completing colonoscopy within the 4-week time window

Patient Acceptability

Patient acceptance scores for stool testing and colonoscopy, discomfort scores, willingness to repeat, assessed by standardized questionnaire.

1. Fecal Test Acceptability Questionnaire, score range: 6 to 30 points. The meaning of the score: A higher score = better results (higher acceptance).

2. Colonoscopy Experience Scale Score range: • Acceptance dimension (Items 1-3) : 3-15 points

   • Comfort/Discomfort dimension (Items 4-6) : 3-15 points (Note direction) Overall experience dimension (Items 7-9) : 3-15 points
   • Total score: 9-45 points Score meaning: A higher score = a better outcome (higher acceptance, less discomfort, and a better overall experience)
3. Willingness for Repeat Examination Score range: 4 to 20 points Score meaning: A higher score = a better outcome (stronger willingness to accept again)

Optimal Cut-off Values

Optimal cut-off values for FIT and FC alone and in combination for predicting UCAN, determined by ROC curve analysis

12-Month Miss Rate

Proportion of new UCAN cases detected during 12-month follow-up among patients with negative baseline colonoscopy