How is HIV AIDS diagnosed?

There are currently three tests that indicate the infection and level of infection of a patient.
ANTIBODY TESTS
Most HIV tests, including most rapid tests and home tests, are antibody tests. Antibody tests check for HIV antibodies in blood or fluids from your mouth. HIV antibodies are disease-fighting proteins that the body produces in response to HIV infection. It can take 3 to 12 weeks for your body to make enough antibodies for an antibody test to detect HIV infection. (In other words, the window period for antibody tests in most people is somewhere between 3 to 12 weeks from the time of infection.) With a rapid antibody test, results are ready in 30 minutes or less. For information on home tests, see below.
COMBINATION TESTS (ANTIBODY/ANTIGEN TESTS)
Combination tests (also called antibody/antigen tests) can detect both HIV antibodies and HIV antigens (a part of the virus) in your blood. A combination test can detect HIV infection earlier than an HIV antibody test can. It can take 2 to 6 weeks for your body to make enough antigens and antibodies for a combination test to detect HIV infection. Combination tests are now recommended for HIV testing that’s done in labs, and they are becoming more common in the United States. However, not all testing sites offer this test by default; if you think you have been recently exposed to HIV, be sure to let your provider know and ask if a combination test is available.
NUCLEIC ACID TESTS (NATS)
Nucleic Acid Tests (NATs) look for HIV in the blood. NATs can detect HIV infection about 7 to 28 days after you have been infected with HIV. NATs are very expensive and not routinely used for HIV screening unless you had a high-risk exposure or a possible exposure with early symptoms of HIV infection.

Thru bloodwork, your CD4 counts, and the copies per ml in your blood, under 50 copies per ml can change you to undetectable.

By lab work
Asking questions about former sex partners.