This was with the Red Cross in Australia. I'm original from the UK and was not allowed to donate before due to CJD worries. The first time I was able to donate, they ran a full test (not sure if they do that for all donations or not) and I got a call back saying they had found markers for blood cancer. As mentioned, follow up tests haven't shown any other markers, and the levels of protein hasn't changed over that time, so have a 6 month wait now for the next follow ups.

I donate platelets with the Red Cross every month and I've got an app where they give me the blood pressure and hemoglobin level, and which used to tell me if I had Covid-19 antibodies before everybody did via vaccine or infection.

Before I donate I have to sign something that says, among other things "We're going to test your blood for AIDS and tell you if you have it, so if you don't want to know don't donate". I hadn't thought about the other things they test for but of course they don't want blood with Leukemia in it either.