Fourth-generation HIV testing can detect both HIV antibodies and p24 antigens, while older versions only search for antibodies. This means that the newer tests can provide a faster diagnosis than the previous ones.
Many clinics and healthcare providers offer free HIV testing. The process is straightforward and usually involves taking a small blood sample, such as from a finger prick.
In this article, we take a detailed look at fourth-generation HIV testing, including the differences from previous tests and what to expect from the procedure. We also discuss reliability and when to test.
Researchers estimate that since 2015, almost 1.2 million people in the United States had HIV, but around 14 percent did not know they had the disease. Regular testing is the best way for a person to determine their HIV status.
Fourth-generation tests detect the virus as quickly as possible, which allows earlier treatment. Studies show that early treatment improves long-term outcomes for people with HIV.
Effective treatment can slow the progression of the virus, protect the immune system, and prevent transmission.
How does a 4th generation HIV test work?
Fourth-generation tests detect two factors in the blood: HIV antibodies and p24 antigens.
When a person becomes infected with HIV, the immune system begins to produce HIV antibodies. This is the body’s method of fighting the virus.
The immune system produces these antibodies in response to p24 antigens.
P24 antigens are part of the virus, and research shows that they usually appear within 2 weeks of HIV entering the body.
A fourth-generation test can reliably detect HIV as soon as a person has become infected with it.
What is to be expected
When a person has an HIV test, the doctor takes a small blood sample. For a fourth-generation HIV test, the provider usually sends the sample to a laboratory for testing.
A person can usually expect their result within a few weeks, although the result may come back in a few days.
If the result is positive, the doctor may arrange for a follow-up test to confirm the results. A positive result means that the person is living with HIV.
After receiving a positive result, it is important to inform all current or former sexual partners so that they can also get tested.
A doctor will advise you on the best course of treatment.
Difference from previous tests
Fourth-generation HIV testing is different from third-generation testing, which can only detect HIV antibodies.
In contrast, fourth-generation tests detect both HIV antibodies and p24 antigens. This allows them to identify the virus earlier than with previous tests.
Fourth-generation tests can detect the virus before the immune system starts producing HIV antibodies. This is because p24 antigens occur before HIV antibodies.
Other available HIV tests include rapid tests and self-test kits. Both may produce results faster than fourth-generation tests, but they may be less accurate.
A person who has done either a rapid test or one from a kit may need to see a doctor for a follow-up test to confirm the results.
For more information and resources about HIV and AIDS, visit our dedicated hub.
Fourth-generation HIV tests can reliably detect the virus as soon as a person has become infected with it.
It is important to note that after contracting HIV, there is a time window in which no test can reliably prove it.
Healthcare providers call this a window of opportunity. It ends when the body starts producing detectable amounts of antibodies or antigens in a process known as seroconversion.
If a person takes an HIV test during their period of time, they may get a false negative result.
In a 2014 study, researchers found that the time span for fourth-generation HIV testing was around 18 days. This means that a person who tests within 18 days of contracting HIV is likely to get a false negative result.
For this reason, it is important that people who may have been exposed to HIV until the period ends wait before taking a test. This would mean waiting 1—3 months after potential exposure.
Fourth-generation HIV testing is now common in the US. A person may be able to access it via:
- healthcare provider
- sexual health clinics
- family planning clinics
- some community centers
In the USA, the Affordable Care Act requires health insurance companies to cover HIV testing without co-payments.
For people without health insurance, some clinics and community centers offer free testing.
Check with a doctor or search online for the nearest location where HIV testing is done. In the USA, a person can use the GetTested search tool.
When should you get tested?
The Centers for Disease Control and Prevention (CDC) recommends that all people aged 13 to 64 years of age take an HIV test at least once as part of their standard healthcare.
However, as with any sexually transmitted infection, it is a good idea to have an annual HIV test.
People at higher risk of contracting HIV should consider testing every 3-6 months. Sharing needles or having sex without a condom, for example, can increase a person’s risk.
Anyone who is concerned they may have contracted HIV should consider testing.
Fourth-generation testing is an accurate method for diagnosing HIV. You can reliably detect the virus 1 month after it is infected by a person.
These tests only require a small blood sample and are available at most health centers. They recognize both HIV antibodies and p24 antigens.
Fourth-generation testing supports early diagnosis and treatment of HIV, which can significantly improve a person’s prospects.
With the right treatment, people with HIV can live long, healthy lives.