Yes, I was trying to think of a "chronic" condition where a test result is sufficient to believe you have the illness (that is, the lack of symptoms is not suff

Yes, I was trying to think of a "chronic" condition where a test result is sufficient to believe you have the illness (that is, the lack of symptoms is not sufficient). But I think we both agree that HIV is a generous case in that the testing is fairly accurate. There are many illnesses with no great tests. The more obscure, the more likely there won't be a test for it. So you end up in a situation where you go to the doctor with a rash and your diagnosis is "an allergy to strawberries or leprosy".