Yan et al. report a blood test that can predict COVID-19 mortality. The authors analyzed 75 clinical features, including the blood-borne biomarkers of 485 infected individuals in Wuhan, and developed a mortality prediction model using machine learning tools. Their modeling identified 3 blood-borne markers that together classified the mortality of patients more than 10 days in advance with more than 90% accuracy. One of these markers alone, the level of lactate dehydrogenase (LDH), was highly indicative of COVID-19 mortality, this test is commonly used to monitor tissue damage associated with a wide range of disorders. The markers and model developed are important because they can possibly help to identify patients that require immediate medical attention. The test could also find use as a surrogate marker to be included in clinical trials of candidate COVID-19 treatments, but additional studies will be required to assess this possibility. The results require validation in larger and independent patient cohorts and call for the development of additional host injury markers, including markers that are cell- and tissue-type specific, to help guide patient management.