For patients in need of blood, it’s fatally important that they receive the right type. That’s why doctors will often give emergency room patients universal donor blood, rather than waiting for the results of a blood test. Blood tests take a long time to process, are expensive, and leave room for human error—putting a vial of blood in the wrong rack, mislabeling it, or sending the chart to the wrong room. If blood tests could be handled right at the point of care, it could revolutionize diagnosis and treatment.