How is AIDS detected?

　　HIV/AIDS can generally be detected through antibody testing, antigen-antibody combination testing, nucleic acid testing, rapid testing, and confirmatory testing.

　　1. Antibody testing: Using serum, plasma, or saliva samples, HIV antibodies are detected using third-generation test reagents. The body gradually produces antibodies 2–12 weeks after infection, and most people can be detected within 4–6 weeks. This method is simple to operate and cost-effective, but false-negative results may occur during the window period; therefore, retesting after 12 weeks is recommended to confirm results.

　　2. Antigen-Antibody Combination Testing: Also known as fourth-generation testing, this method simultaneously detects HIV antigen (P24 protein) and antibodies. The antigen appears about two weeks after infection, while antibodies develop within 2–4 weeks. The window period is shortened to 2–4 weeks, and the test sensitivity is higher, allowing for earlier detection of infection. It is currently a commonly used initial screening method.

　　3. Nucleic Acid Testing (NAT): This directly detects HIV viral RNA in the blood and can identify infection within 1–2 weeks, offering the shortest window period. It is often used for very early screening after high-risk exposure and for diagnosing infections in newborns. However, it is more expensive, and false-negative results may occur due to low viral load, so results should be confirmed with other tests.

　　4. Rapid Testing: Including methods such as colloidal gold assays, this approach quickly provides preliminary results using finger-prick blood or saliva samples, with results available within 15–30 minutes. It is suitable for emergency screening or self-testing scenarios. However, rapid test results are for reference only, and positive results must be further confirmed with a confirmatory test.

　　5. Confirmatory Testing: If initial screening tests are positive, samples must be sent to a Center for Disease Control and Prevention (CDC) for confirmation using Western blot (WB) or recombinant immunoblot assay (RIBA). These tests have high specificity and can accurately determine whether infection is present. They are critical steps in confirming an HIV/AIDS diagnosis and provide reliable and accurate results.

　　HIV testing should consider multiple methods comprehensively, as each testing method may carry some degree of error and uncertainty. Therefore, it is recommended to undergo testing and diagnosis under the guidance of a qualified healthcare professional.