3627 Background: Blood-based colorectal cancer (CRC) screening tests can improve adherence to screening guidelines. Yet, current commercially available options have poor sensitivity and specificity inhibiting incorporation into routine clinical care. Here we report the validation of a blood-based test for the detection of colorectal cancer and advanced neoplasia. Methods: This blood-based test aims to detect colorectal neoplasia by identifying tumor-associated biomarkers including genomic or epigenomic (methylation and fragmentomics) signatures in cell-free DNA (cfDNA). cfDNA is partitioned based on methylation level, enriched for informative genomic regions, and sequenced. This novel workflow enables high-fidelity analysis of multi-modal information in majority of extracted cfDNA molecules. Results are integrated into a binary “detected” versus “not-detected” result using a proprietary bioinformatic pipeline (Guardant Health, USA). The assay was trained on samples obtained from >6,000 unique individuals (2,685 cancer-free and 1,698 with advanced colorectal neoplasia (ACN) for training, 1,072 cancer-free and 551 with ACN for threshold setting). The thresholds were frozen prior to validation targeting a specificity of > 91.5%. Each aspect of the validation study followed Nex-StoCT CLIA working group and CLSI guidelines. Results: Limit of detection (LoD) was established across six dilutions. Even for low cfDNA mass inputs of less than 4ng, the 95% LoD was determined to be less than 1 tumor-derived genomic equivalent (0.5), indicating over at least 10-fold increase in assay sensitivity compared to best-in-class assays for somatic mutation detection. Precision studies in 60 positive and negative replicates from clinical samples yielded >90% average positive and negative percent agreement both within and between batches. Endogenous interference studies yielded > 90% positive and negative percent agreement between reference control and common endogenous substances, including albumin, bilirubin, hemoglobin, triglycerides, and genomic DNA, in clinical positive and negative samples and minimally manipulated samples. The clinical validation of the test was conducted in > 300 cases (biobanked pre-operative cohort for CRC cases and screening cohort for advanced adenoma and negative cases). Conclusions: Here we present the validation of a multi-modal blood-based test for the detection of colorectal cancer. This test is currently being evaluated in a registrational study (ECLIPSE: NCT04136002).