A liquid biopsy assay is a diagnostic test that uses a sample of a patient's blood to detect the presence of cancer cells, genetic mutations, or other biomarkers associated with cancer. The test is used to detect and monitor cancer in an early and non-invasive way. Liquid biopsy assays are used to detect and monitor cancer in patients who have a high risk of developing the disease or who have already been diagnosed with cancer. The assays can also be used to monitor the effectiveness of cancer treatments.