Tuesday, the FDA's staff reviewers raised concerns regarding Guardant Health Inc's (NASDAQ:GH) experimental blood test for colorectal cancer, suggesting it might not detect some tumor types that could become cancerous.  Guardant Health is seeking approval for Shield, a blood-based colorectal cancer (CRC) screening test for average-risk adults.  Shield is an in vitro diagnostic device intended for the qualitative detection of CRC through sequencing the cell-free DNA (cfDNA) isolated from whole blood. Related: Cancer Test Focused Guardant Health Stock Falls On FDA AdCom Update For Colorectal Test. The FDA document noted, "Patients with advanced neoplasia (AA) have a high risk of developing CRC cancer. The Guardant ECLIPSE study demonstrated 83.1% sensitivity ...