Supplementary Material for: False-positive liquid biopsy assays secondary to overlapping aberrant methylation from non-cancer disease states

Introduction: Liquid biopsies are increasingly being adopted in the care of patients with cancer. Not only in patients with metastatic disease but the utility is also being recognized in earlier phases of the journey of a patient with cancer. More recently, methylated platforms are offering another lens of looking at the same question more so in minimal residual disease (MRD) and early detection settings. While false positives secondary to clonal hematopoiesis of indeterminant potential (CHIP) is recognized as one entity to consider when interpreting these assays and advanced CHIP filtering bioinformatics platforms can prevent this, false positives secondary to aberrant methylation is not described. Case presentation: Herein, we report a case of a patient with hepatitis C related viremia and a very high viral load that had a false positive plasma-only colorectal MRD assay. The colorectal MRD assay spontaneously cleared on HCV therapy which led to clearance of the virus. Conclusion: As these assays are increasingly applied in real-world settings, it would be of value to consider non-cancer chronic disease states that may lead to aberrant methylation that could lead to a false positive assay.