How to communicate a ‘positive’ result (from a blood test) that is actually negative for the user?

I'm designing an app for a doctor with a list and detail view of blood tests. What's important is to see if the test has a negative (you don't have the disease) or positive (you have the disease). I was wondering if anyone has a good idea for the visual design because it feels strange to use red/green or a checkmark/cross or something similar.