HIV Testing

Medically Reviewed on 1/8/2024

HIV (human immunodeficiency virus) testing facts

Every adult can benefit from undergoing HIV testing at least once.
Every adult can benefit from undergoing HIV testing at least once.
  • Human immunodeficiency virus (HIV) testing is done to diagnose those who are newly infected, identify previously unrecognized infections, and relieve the minds of those who are not infected.
  • There were more than 36,000 new HIV infections as of 2021 in the US. About 13% of those infected didn't know they had HIV.
  • New sexual partners should consider getting an HIV test before sex to inform themselves of how to keep from getting HIV. There is no vaccine, but there are other prevention methods.
  • Every adult can benefit from being tested for HIV at least once. Voluntary routine HIV testing has been shown to be as cost-effective as screening for conditions like high blood pressure or breast cancer, even in low-risk people.
  • HIV testing is important because HIV is highly treatable. The sooner a person learns they have HIV, the sooner they can start treatment and live a fairly normal life. Treatment also prevents infection of others.
  • The quality of life and long-term prognosis of HIV is excellent with once-daily oral (pills) or even monthly injectable treatment, even in "advanced" HIV or AIDS.

What is the human immunodeficiency virus (HIV)?

HIV is short for the human immunodeficiency virus. This virus causes acquired immunodeficiency syndrome or AIDS. HIV is a complicated virus. It reproduces mainly in specialized cells of the body's immune system called CD4 lymphocytes. As HIV replicates itself, the CD4 cells are destroyed. As more and more cells die, the body loses the ability to fight many infections. If the number of CD4 cells in the bloodstream falls below 200 per cubic millimeter, or if specific health conditions occur, the person is defined as having AIDS. These health conditions include infections and cancers that take advantage of the suppressed immune system. Regardless of the CD4 count, people with untreated HIV infection carry the virus and can spread it to others through unprotected sex or contact with blood or certain other body fluids.

Undiagnosed HIV infection is responsible for continued transmission. In the US, of 1.2 million estimated cases in individuals over 13 years of age as of December 2021 (US Centers for Disease Control and Prevention [CDC] estimates), about 13% were unaware of their infection. Thus, an HIV test is important to diagnose those who are newly infected, identify previously unrecognized infections, and relieve the minds of those who are not infected. HIV testing also reduces the risk of transmission during pregnancy, blood transfusions, and tissue transplantation.

Does HIV have different strains?

HIV has different subtypes. HIV testing in the US may screen for one or two subtypes, either HIV-1 alone, or both HIV-1 and HIV-2. HIV-1 is the commonest, “classic HIV” subtype found throughout the world. HIV-2 is related, but is lower in transmissibility and slower in progression. It is found in people from West Africa. It accounts for only 0.01% of HIV infections in the US.

QUESTION

What is HIV? See Answer

When should you get tested for HIV?

HIV testing is not limited to suspected exposure situations such as unprotected sex or IV drug use. Events such as National HIV Testing Day have raised awareness and increased participation in testing.

HIV testing is part of routine medical practice similar to tests that screen for other diseases. The CDC recommends a routine HIV test for all adolescent and adult patients aged 13 to 64 in all health care settings, in all cases of pregnancy, and all newborns of those with HIV at the time of delivery.

People who are at high risk for acquiring HIV should undergo annual HIV testing at minimum. In addition, health care professionals request or require testing as part of evaluation and treatment for other conditions, such as women undergoing treatment with assisted reproductive technologies for infertility or treatment of viral hepatitis. Healthcare personnel and first responders may be exposed on the job and require HIV testing.

In some cases, HIV testing may be required by law. This occurs for blood used for transfusions, organ donors, and military personnel. States may select additional populations for mandatory testing.

Since 2006, the CDC recommends against written consent for HIV testing in health care facilities because it avoids unwarranted stigma and simplifies screening. HIV test consent can be included in general medical informed consent forms as long as patients are informed that HIV testing will be performed as routine, unless they opt to decline (“opt-out” of screening). In addition, HIV testing may be performed when a high-risk occupational exposure to blood or body fluids has occurred and the “source” person refuses or is unable to consent to testing. As of 2024, almost all states have HIV testing laws consistent with CDC guidance.

How is HIV testing done? What are the types of HIV tests? What should I expect?

HIV testing is performed on blood (most common) and saliva, depending on the type of test. It is important to know that there is a “window period” between getting infected with HIV and when it becomes detectable. This means that depending on the type of test, HIV may not be detectable anywhere between 10 and 90 days after infection. If you strongly suspect you were exposed to HIV and initial testing is negative, you should avoid activities that may infect others and talk to a healthcare professional about when to repeat an HIV test.

The three types of HIV tests include:

1. HIV Antigen/Antibody (Ag-Ab) tests: These tests can be done from blood drawn from a vein or fingerstick. The HIV Ag-Ab test combines detection of antibodies directed against HIV-1 and HIV-2, as well as p24 antigen. This antigen (protein) forms part of the core of the virus, so p24 antigen is detectable in the blood earlier after infection. These tests may be referred to as “4th generation” screening tests (as opposed to “3rd generation” tests for HIV antibody alone). They allow for earlier detection of HIV infections and are the preferred as first-line for screening.

HIVAg/Ab may detect HIV as early as 18 days after exposure, and false negative rate is very low if performed within 4-6 weeks of exposure. Thus a person who tests negative at least 4 weeks after exposure can be fairly confident that it is truly negative. However, if positive, HIV Ag/Ab does not distinguish which subtype is present, so additional testing is required.

2. HIV Antibody tests: When someone is infected, HIV hijacks human cells to produce more HIV viruses and proteins. The body makes HIV antibodies that tag those proteins for elimination by the immune system. HIV antibody production may take several weeks. Once a person has HIV antibodies, they will typically always be detectable even if HIV infection is undetectable by other tests due to treatment (see HIV Nucleic Acid Test [NAT] below). Unlike other viruses, HIV antibodies do not eliminate the virus, but their presence is a marker that someone is infected with HIV.

Antibody testing can be done on blood from a vein, a finger stick, or saliva. Detection is earliest in vein blood vs. finger stick and saliva. In this test, a person's serum is allowed to react with virus proteins that have been produced in the laboratory. If the person has been infected with HIV, the antibodies in the serum will bind to HIV proteins, and the extent of this binding can be measured.

Most HIV antibody tests detect HIV-1 and/or HIV-2 within 23 to 90 days after exposure. These tests will report detection of HIV-1, HIV-2, or both.

Rapid HIV Testing: There are some rapid HIV testing kits on the market that can be used in a health care professional's office or other points of care, as well as self-testing kits for use at home.

Home HIV Self-Testing: The OraQuick In-Home HIV Test was approved by the US FDA in 2012. It is sold online and in drug stores. The test detects HIV-1 antibody. It involves swabbing the upper and lower gums with a test stick, placing it in a tube with test fluid, and waiting up to 40 minutes to see if one line (negative) or two lines (positive) appear.

Both blood and saliva antibody testing are 99.9% accurate at predicting that there is no HIV in the sample (high “negative predictive value”). But because levels of HIV are higher in blood than in saliva, the saliva test is slightly more likely to miss HIV. OraQuick is 92% sensitive, but one in 12 people with HIV might test false-negative, especially if performed less than three months after exposure. A person who tests negative with OraQuick but strongly suspects an HIV exposure should get a more sensitive blood test performed by a lab. (See HIV Antigen/Antibody [Ag/Ab] test and HIV Nucleic Acid Test [NAT])

3. HIV Nucleic Acid Test (NAT): HIV NATs detect the HIV virus itself in a person's blood by detecting the HIV ribonucleic acid (HIV RNA) or genetic material, therefore it may be used as a “confirmatory test” for HIV infection. An HIV polymerase chain reaction (PCR) test is a type of NAT. A NAT may be “confirmatory” on its own without additional testing for diagnosis of HIV infection. For example, NAT tests are important for newborn screening since maternal HIV antibodies may cross the placenta and be detected in the newborn even without infection. However, some are not approved by FDA as “diagnostic”, and they are more costly, so NAT is not commonly used as a first-line screening test for HIV.

HIV NAT can detect HIV infection over 99% of the time, as early as 10 to 33 days following exposure. Different HIV NAT tests may test for HIV-1 alone or both HIV-1 and HIV-2. They may also be qualitative (detects virus but not the level in the blood) or quantitative (detects virus and the level of virus):

  • Qualitative HIV NAT– Detects HIV-1 and/or HIV-2 without determining the level of virus in the blood. Used for making the diagnosis of HIV infection. Qualitative NAT is reported as “Positive” or “Negative” without a number value.
  • Quantitative HIV NAT– Quantitative NAT is reported as “Reactive” with the number of viral copies per milliliter, or “Nonreactive” or “Undetectable”. The most common ones detect HIV-1 virus plus the level of virus in the blood, commonly called an HIV “viral load”. Quantitative HIV-2 NAT is only used in the rare case of suspected or known HIV-2 infection. These tests may be used for diagnosis, at the start of HIV-1 therapy, and/or for monitoring effectiveness of therapy.

In the US, a three-step sequence of tests is recommended by CDC as follows.

  1. Perform HIV Ag/Ab test first.
    1. If negative, no further testing is needed.
    2. If positive, perform HIV-1/2 Antibody to determine the subtype.
      1. If positive, perform HIV-1 qualitative or quantitative NAT. Quantitative is best if available, since an HIV viral load is needed at the start of treatment anyway.
        1. If positive HIV-1 NAT, HIV-1 diagnosis is confirmed.
      2. If negative, and risk factors for HIV are low, then the above tests are considered false positive.
      3. If negative, but there is high likelihood of HIV exposure less than 1 month prior, it may be too early to detect the virus. In this case, repeat HIV-1 NAT in 2 to 4 weeks.
      4. Any additional HIV-2 NAT or HIV 1/2 Ag/Ab testing is generally needed only if there is a strong suspicion of HIV-2 exposure. See Does HIV have different strains?

In cases where the above procedure is not followed, or this sequence of tests is not available, the diagnosis of HIV might be made by two positive HIV antibody and/or HIV Ag-Ab tests in any combination (preferably different types or brands) or one positive HIV NAT. Additional tests by an Infectious Diseases or HIV specialist may be considered.

Keep in mind that no test is perfect; tests may be falsely positive or falsely negative or impossible to interpret (indeterminate, see How accurate are HIV tests? What is meant by a false negative or false positive test?)

Lastly, because HIV is transmissible to others and has serious health impact on individuals, the public, and the healthcare system if untreated, positive tests performed in a laboratory are reported to the state health department in all 50 states and include the patient's name. State health departments report results without identification to the CDC for public health disease monitoring. However, due to the psychological and social impact of this test result, there are a number of strict federal and state laws, as well as the Health Insurance Portability and Accountability Act (HIPAA) of 2003, that exist to protect patient privacy and limit disclosure of test results only to those who need to know in order to protect the public and individuals from transmissible diseases. You may be contacted by the health department if your test result is positive. However, names remain confidential and by federal law cannot reported to employers, family members, or anyone else not directly affected without your written consent. Some states allow anonymous testing in which the patient's name is never recorded. Home test results are not reported unless additional laboratory confirmation is performed.

What is a detectable HIV viral load? What viral load is normal? What level of viral load is undetectable?

Quantitative HIV NAT is often referred to as an “HIV viral load” test and some can be used to both diagnose HIV and to estimate the level of HIV in the blood. HIV NAT is highly sensitive and can detect as few as 20-40 copies of virus per milliliter of blood depending on the test. Any level of detectable virus on HIV NAT is not normal. Anything below this “lower limit of detection” is considered an “undetectable” viral load.

The goal of HIV treatment is to suppress the level of virus in blood to completely undetectable by a quantitative HIV NAT. This dramatically reduces progression of disease, long-term complications, and transmission of HIV to sexual partners (hence Infectious Diseases and HIV specialists will often say that “undetectable is untransmittable”).

Can I test HIV positive if my viral load is undetectable?

Yes, HIV antibody tests and HIV Ag/Ab tests will usually remain positive for life even with highly effective treatment that fully suppresses HIV viral load to undetectable. Rarely, some people will have positive HIV antibodies and undetectable HIV virus even without treatment. These may be false positive tests or rare individuals (“long-term non-progressors” or “elite controllers”) whose bodies are able to clear or control the HIV infection.

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How long does it take to get HIV test results? What do the test results mean?

It takes time after exposure for HIV tests to detect a new HIV infection, anywhere between weeks to months, depending on the test. Timing of results also varies depending on the test, the laboratory, and whether it is an OraQuick In-Home test kit. Depending on the test(s) performed, it might take an hour to a week to get negative screening test results, and usually 2 to 3 more weeks for final positive confirmation of a positive screening test.

Results from antibody tests that are sent to a laboratory usually take one to three days to return, but if an antibody test is positive, it is considered preliminary until a confirmatory test is performed. For example, results from rapid tests done in the healthcare professional's office or at other points of care are usually available in 15-20 minutes. If the rapid test is positive, it is still necessary to send blood to a laboratory for confirmatory testing. NAT testing results usually take a few days to a week depending on the lab.

What test results mean, in general:

  • Positive HIVAg/Ab: This screening test suggests that you have HIV. It should be confirmed by specific HIV antibody testing. HIV NAT may be considered.
  • Negative HIV antibody or Ag/Ab test:
    • If you were tested routinely and do not have risk factors for HIV infection, you very likely do not have HIV.
    • If exposure to HIV is suspected, you may need additional testing.
  • Positive HIV antibody: This screening test suggests that you have HIV. It should be confirmed by additional testing.
  • Unclear (indeterminate) HIV antibody: The test cannot tell whether HIV antibody is present. Alternative testing may be an HIV Ag-Ab or HIV NAT.
  • Any combination of two positive HIV antibodies and/or HIVAg/Ab, OR one positive HIV NAT: You have HIV infection. You should not donate blood products or exchange blood or body fluids with someone else until you see an Infectious Disease or HIV specialist for evaluation and treatment. Do not have sexual contact with someone else without a male or female condom. Do not share IV needles with someone else. See HIV prevention section

How accurate are HIV tests? What is meant by a false negative or false positive test?

The current testing protocols are highly accurate. Both blood and saliva HIV antibody testing are 99.9% accurate at predicting that there is no HIV in the sample (high “negative predictive value”), so you can be confident in a negative HIV antibody result. However, no test is perfect. HIV antibody tests are highly accurate, but less so than HIV Ag-Ab, which is less so than HIV NAT. Vein blood allows detection earlier than finger stick blood, while saliva is least likely to be detected as early as vein and finger stick blood.

The probability of a false result on HIV testing is low but depends on the timing of the test after exposure, the type of test performed, and the person's risk factors for getting infected.

False negative tests occur in people who are truly infected with HIV but have negative tests. Among 100,000 people who are truly infected, rapid tests will be falsely negative in zero to 8 people by 4 to 8 weeks using current HIV screening tests. Negative antibody tests in people infected with HIV may occur because antibody concentrations are low or because antibodies have not yet developed in the early weeks after infection. Since HIV antibodies take about three weeks or longer to reach detectable levels, falsely negative tests may occur during this “window period.” HIV Ag/Ab testing shortens this timeframe.

False positive tests occur when uninfected people have positive results. In a community where HIV is uncommon, false positives will be much more likely than a community where HIV is very common. Thus, a single positive test may not rule out or rule in the diagnosis. This is why all positive initial tests must be confirmed with a follow-up confirmatory test. When both tests are positive, the likelihood of a person being HIV infected is >99%.

HIV testing in pregnancy and newborns

HIV transmission to newborns is highly preventable, and undiagnosed HIV during pregnancy is not rare. Routine testing to detect undiagnosed HIV during pregnancy benefits the health of the mother in addition to preventing HIV infection of the fetus or newborn. With proper management, the probability of transmitting HIV from the mother is less than 2%. Without proper management, the risk of transmission is as high as 33%. Since HIV testing and perinatal treatment guidelines were adopted in the 1990s, transmission during delivery or breastfeeding has dramatically dropped by over 90%.

HIV testing is recommended at the beginning of each pregnancy during prenatal care. HIV is transmissible at any time, but is most often transmitted during the third trimester or at the time of delivery. HIV may also be transmitted during breastfeeding if the mother is untreated. If HIV risk factors are present or there is a high incidence of HIV in the population, testing should be repeated in the third trimester to allow treatment during the highest risk period for transmission. An HIV specialist or obstetrician familiar with HIV management can help weigh the risks, benefits, and the best timing of HIV treatment during pregnancy; there is no one right answer for all pregnant individuals.

If HIV testing was not performed during pregnancy, it is recommended to test both mother and newborn soon after delivery; if breastfeeding is planned, breastmilk can be stored until after test results return negative. It is strongly recommended that all children born to pregnant individuals with HIV also be tested if screening did not occur with those pregnancies.  

What is the prognosis for a positive HIV test?

The prognosis for someone with a positive HIV test in the US is excellent because there is excellent once-daily oral treatment available for HIV (antiretroviral therapy). Some may be good candidates for injectable therapy every one to two months. If a person with HIV adheres to taking their HIV medicine and maintains an undetectable viral load, life expectancy can be quite normal. People with undetectable HIV can achieve a normal immune system, work without restrictions, enjoy fulfilling relationships and even parenthood, with the confidence that they will not transmit to loved ones and children. This is far from the dreaded prognosis of decades past, before highly effective antiretroviral therapy.

Counseling and HIV testing

Counseling is not required before an HIV test. Almost all states follow an “opt-out” policy of HIV testing in accordance with CDC recommendations. This approach eliminates as many barriers as possible to HIV testing. Simplified opt-out programs have resulted in the earlier diagnosis, treatment, and transmission prevention for many people with HIV.

While HIV prevention counseling can be beneficial in some groups, mandating it as a condition of all HIV testing adds both a time burden and barrier to testing for both healthcare providers and people who would benefit from testing. Studies show the benefit of counseling is greatest for those who have tested positive for HIV, who then adopt precautions to prevent transmission. Risk reduction of pre-test counseling is less clear in HIV-negative individuals.

Counseling about HIV after testing should cover how to prevent HIV infection, what the HIV test means, and any needed next steps or referral to an Infectious Disease or HIV specialist.

Where can you get tested for HIV? Where do you find HIV testing sites?

Almost any licensed healthcare provider or walk-in clinic offers HIV testing. You can check with your health insurance provider and verify your laboratory testing locations and coverage if this option is available to you.

CDC offers a locator site for fast, free or reduced cost HIV testing, condoms, and HIV prevention services at GetTested. Some clinics only provide HIV testing, but sexually transmitted diseases (STDs) clinics routinely provide HIV testing along with testing for diseases like chlamydia, gonorrhea, syphilis, and herpes.

Various commercial laboratories offer confidential HIV and STD testing as a self-paid option but will typically provide results and recommend more personalized interpretation by a licensed healthcare provider.

More information for HIV testing

The CDC website is an excellent source of science-backed information:

https://www.cdc.gov/hiv/testing/index.html

Medically Reviewed on 1/8/2024
References
United States. Centers for Disease Control and Prevention. "HIV Testing." Updated June 9, 2022. Accessed January 1, 2024.
https://www.cdc.gov/hiv/testing/index.html

United States. Centers for Disease Control and Prevention. "HIV Guidelines." March 28, 2022. Accessed December 31, 2023.
https://www.cdc.gov/hiv/guidelines/index.html

U.S. Department of Health and Human Services. Office on Women’s Health. “Pregnancy and HIV.” Updated February 18, 2021. Accessed January 2, 2024.
https://www.womenshealth.gov/hiv-and-aids/living-hiv/pregnancy-and-hiv

United States. Centers for Disease Control and Prevention. “2018 Quick reference guide: Recommended laboratory HIV testing algorithm for serum or plasma specimens.” Updated January 2018. Accessed December 31, 2023.
https://stacks.cdc.gov/view/cdc/50872

United States. Centers for Disease Control and Prevention. “State HIV Testing Laws: Consent and Counseling Requirements.” Updated March 8, 2017. Accessed January 1, 2024.
https://www.cdc.gov/hiv/policies/law/states/testing.html