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Background: Since 2013, the Shanghai municipal government has been offering free colorectal cancer screening services (FOBT) to community residents aged 50-74. By 2023, 3.044 million people had participated in it while many residents do not especially those under 65 years old. According to follow-up data, less than 30% of individuals who tested positive on the initial screening have undergone diagnostic colonoscopies. This study applies the Health Belief Model to analyze factors influencing residents' participation in initial screening and colonoscopy for colorectal cancer in Shanghai, which will provide evidence for improving the effectiveness of the screening program. Methods: This study was conducted through stratified random sampling across all 248 community health service centers in Shanghai. A total of 7,936 questionnaires were collected, with 7,601 deemed valid. The interviewed residents completed the Chinese version of The Champion Health Belief Model Scale. The “perceived barriers” items for initial screening and colonoscopy participation willingness were different and reverse-scored separately. The study analyzed the impact of each dimension on residents' willingness to participate in colorectal cancer initial screening or colonoscopy through logistic regression models, and conducted heterogeneity analysis by subgroups. Findings: For the willingness to participate in initial screening, the total score for 5,635 residents who had participated in initial screening was 120.3±10.4 points, compared to 115.2±11.4 points for the 1,966 residents who had never participated (p

Background: Screening for colorectal cancer (CRC) and precancerous colorectal adenoma (CRA) can detect curable disease. However, participation in colonoscopy and sensitivity of fecal heme for CRA are low. Methods: Microbiota metrics were determined by Illumina sequencing of 16S rRNA genes amplified from DNA extracted from feces self-collected in RNAlater. Among fecal immunochemical test-positive (FIT+) participants, colonoscopically-defined normal versus CRA patients were compared by regression, permutation, and random forest plus leave-one-out methods. Findings: Of 95 FIT+ participants, 61 had successful fecal microbiota profiling and colonoscopy, identifying 24 completely normal patients, 20 CRA patients, 2 CRC patients, and 15 with other conditions. Phylum-level fecal community composition differed significantly between CRA and normal patients (permutation P = 0.02). Rank phylum-level abundance distinguished CRA from normal patients (area under the curve = 0.767, permutation P = 0.006). CRA prevalence was 59% in phylum-level cluster B versus 20% in cluster A (exact P = 0.01). Most of the difference reflected 3-fold higher median relative abundance of Proteobacteria taxa (Wilcoxon signed-rank P = 0.03, positive predictive value = 67%). Antibiotic exposure and other potential confounders did not affect the associations. Interpretation: If confirmed in larger, more diverse populations, fecal microbiota analysis might be employed to improve screening for CRA and ultimately to reduce mortality from CRC.