The Galleri blood test, created by Grail, has generated excitement for its ability to detect signals from 50 types of cancer. In trials, it demonstrated a 62% positive predictive value, meaning that 62% of those who tested positive actually had cancer. However, this also means that 38% of positive results were false alarms. The test's specificity is high, with a 99.6% success rate in correctly identifying those without cancer. Yet, its sensitivity is concerning at only 40.4%, indicating that it misses about three out of five cancers. This raises the risk of false reassurance for patients. While the test could be a valuable tool in future screening programs, its limitations and high cost of $949 in the US suggest it is not a standalone solution for cancer detection.