Background: The National Polyp Study and 2021 USPSTF CRC-update highlight that the detection and removal of precancerous advanced adenomas (AA) prevents colorectal cancer (CRC), decreases mortality, and leads to higher cost savings than early cancer detection. Performance of a multimodal blood-based test for the detection of CRC and AA that integrates sensitive and accurate detection of circulating gastrointestinal epithelial cells and somatic oncologic variants as well as SEER data of the impact of sex and age is described. Methods: The prospective study included average-risk, asymptomatic screening subjects from 18 geographically dispersed US colonoscopy centers with blood drawn before colonoscopy. Monte Carlo cross-validation (MCCV) methods were used to evaluate the robustness of test performance through 2000 iterations of independent training and validation using bootstrap resampling with stratification to balance patient histopathology, age, and gender. Results include point estimates, confidence intervals, and distributions of sensitivity and specificity to detect AA and CRC. Results: The study cohort (53.2% female; mean age 56.7 yrs.) consisted of 1,038 subjects (White 65.1%; Black 8.5%; Hispanic 24.8%; Asian 1.7%); of which 954 (92%) were asymptomatic, average-risk screening subjects without age enrichment (including 11 CRC and 93 AA) and 84 (8%) were enriched case-control (65 CRC and 19 AA) subjects. The algorithm derives a test score from 0 (low risk) to 100 (high risk) as a quantitative measure of AA and CRC risk. A pre-defined cut point of 47.2 yields a test specificity > 90%, and 92.1% and 54.5% sensitivity for the detection of CRC and AA, respectively. Estimated sensitivities and selected Clopper-Pearson (Exact) 95% confidence intervals based on validation results from MCCV are presented. A split analysis shows for the 954 intended-use, asymptomatic, average-risk screening subjects, the sensitivity for CRC and AA are 100% and 55.9%. Conclusions: A multi-site, prospective, average-risk CRC screening study using a multimodal assay had high sensitivity and specificity for AA and CRC. The quantitative correlation of test scores with disease pathology indicates that the modes of the assay interrogate the primary underlying pathophysiology of disease. The results demonstrate the potential of this novel test to meet the clinically unmet need for a noninvasive strategy for CRC screening and prevention that detects CRC and AA. Clinical trial information: NCT05127096.