What Is the Rapid HIV Test?
It is now clear from a number of studies that getting treatment as soon as possible after becoming infected with HIV is better than waiting. HIV-infected patients who are treated early have fewer complications from HIV infection and are less likely to infect other people than those who wait to be treated. Studies also show that people who know they are HIV-positive may change their behavior to decrease the risk of infecting others.
The U.S. Centers for Disease Control and Prevention (CDC) now recommends that all people between the ages of 13 and 64 get tested for HIV regardless of risk.
HIV testing is also recommended at least once a year for those at higher risk of getting HIV infection. These include
- people who use injection drugs and share needles or syringes;
- people who have unprotected sex (vaginal, anal or oral) with men who have sex with men (MSM), or with people who have sex with multiple partners or anonymous partners;
- people who exchange sex for drugs or money;
- people who have been diagnosed with hepatitis, tuberculosis (TB), or an STI (sexually-transmitted infection) such as chlamydia, gonorrhea or syphilis; and
- people who have unprotected sex with someone with any of the above risk factors.
There are now two categories of HIV tests: conventional and rapid. Conventional tests are those in which blood or oral fluid is collected and then sent to the lab for testing. Results from conventional tests are typically available in a few hours to a few days. Rapid tests, however, can be done directly at the point of care and yield results in 15-20 minutes, while you wait.
In October 2004, conventional HIV testing was changed when OraSure Technologies, Inc., announced that it had U.S. FDA approval for a rapid HIV test that can detect antibodies to both HIV-1 and HIV type 2 (HIV-2). This is called the OraQuick Advance Rapid HIV-1/2 Antibody Test. It was the first available test that could provide results in 20 minutes using oral fluid, a finger-stick sample of blood, or plasma. Rapid HIV testing is now highly recommended and has become the mainstay of most HIV screening programs.
What Are the Advantages of a Rapid HIV Test?
The rapid test allows for testing of more individuals. According to the CDC, 1.2 million Americans have HIV, but up to one in eight don't know it. About 44,000 Americans per year become infected with HIV. This number has decreased recently due, in part, to more testing. Among those who get tested using traditional (non-rapid) methods, 31% of those who test positive do not return for their results (which are typically available one or more weeks after the test is done).
People give a variety of reasons for not returning for their test results. The frequency of each response depends on the population being tested. The most commonly given reasons include the following:
- Fear of a positive result
- Lack of transportation
- Relocating to a new city
- Belief that they are at low risk for HIV and therefore the result will be negative
- Fear that their HIV status will be disclosed to someone else
Significant benefits of the rapid HIV test include the following:
- Providing quick results eliminates the need for people to return to get their results, although positive results must be confirmed by an additional test.
- People who do not like needlesticks or are otherwise afraid of a blood test may decide to be tested.
- If people know immediately that they are positive for the HIV virus, they can begin to receive treatment sooner and to take steps to prevent transmission of the virus.
- The tests do not require specialized equipment.
- An oral test is less dangerous to the tester. With an oral test, there is no risk to a health-care worker of accidentally being pricked by a needle or being exposed to blood. HIV cannot be transmitted by oral fluid.
Both conventional and rapid tests can be further divided into third-generation antibody tests or fourth-generation combination antigen/antibody tests. The third-generation antibody tests detect antibody to HIV, which is a protein that the body makes in response to an HIV infection. The fourth-generation tests both antibody and antigen, which is a protein of the HIV virus itself. The main difference between the third- and fourth-generation tests is the "window period" or how quickly after a new infection the test can show positive results. The window period for current third-generation tests is 22 days, meaning it could be as long as 22 days between the time of infection and the test showing a positive result. The window period for the fourth-generation tests is as much as one week. People who take an HIV test during the window period after a possible exposure to HIV are advised to come back later to take another test.
Once important difference between the conventional laboratory test and rapid tests is the ability to detect very early or acute HIV infection. This is done with the addition of an HIV RNA PCR or NAT (nucleic acid amplification) test. HIV RNA appears in the blood within the first few days of infection. If the antibody test is negative but the NAT is positive, this may indicate that the patient is very newly infected. NAT testing is also used to confirm a positive result of the third- or fourth-generation test. Western Blot testing is no longer routinely used.
What Is the Accuracy of the Rapid HIV Test?
In 20 minutes, the device indicates whether HIV-1 or HIV-2 antibodies are present. If one line appears on the strip, it means that the person is not infected with HIV (with 99.8% accuracy). If two lines appear, the person is likely infected (99.3% accuracy). If the result is positive, it has to be confirmed by sending blood to a laboratory. The confirmation test may take one to five days, depending on the lab. As with all antibody tests for HIV, it could take from two to four weeks for a newly infected person to develop antibodies to the HIV virus and thus test positive for HIV. Therefore, if there is a negative result and a possibility of a recent exposure to HIV, the test must be repeated.
These rapid tests have revolutionized HIV screening by making testing available in many clinics, emergency departments, and temporary testing sites such as at health fairs and special HIV testing events.
Hospitals use these rapid HIV screening tests to tell if health workers have been exposed to HIV-infected blood and to test women in labor who had not been previously checked. This way, exposed workers and newborns can get anti-HIV drugs immediately to possibly prevent infection. In 2003, the CDC emphasized the use of these rapid HIV screening tests at shelters, drug treatment centers, and other nonmedical facilities.
How Is the Rapid HIV Test Performed?
To perform a rapid test, the tester collects either oral secretions or a drop of blood from a finger-stick sample. For oral secretions, the device involves swabs once around both the upper and lower gums. The tester then inserts the device into a vial containing the developing solution.
What Is the Cost of the Rapid HIV Test?
The cost for the rapid HIV test, whether it uses oral fluid or a finger-stick blood sample is about $8 per test for public health officials and $8-$60 for other organizations. Most insurance plans now cover HIV testing.
There are several rapid tests available which can be done on either whole blood from a vein (venipuncture) or finger stick, or oral fluids collected on a special swab. Many of these tests also can detect HIV-2, which is a different virus than HIV-1.
HIV-1 is the retrovirus that typically causes AIDS and is the HIV type most prevalent in most of the world, including the United States. If a person has antibodies to HIV-1, it means that he or she is infected with the HIV-1 virus that causes AIDS.
HIV-2 is a virus found primarily in western, sub-Saharan Africa. HIV-2 is rare in other parts of the world, but it has been reported sporadically in many locations. It is believed to be spread by the same methods of transmission as HIV-1. If a person has antibodies to HIV-2, it means that he or she is infected with the HIV-2 virus.
Testing for both HIV-1 and HIV-2 is important, particularly in people who may have acquired their infection in West Africa or from someone who may have links to that area. Much of the HIV testing currently done in the United States, including the rapid oral test, detects both HIV-1 and HIV-2 (for example, the test used by the American Red Cross to screen blood donations).
Available rapid tests include the following:
- OraQuick Advance Rapid HIV-1/2 Test Antibody Test (whole blood, plasma, oral fluid)
- Reveal Rapid HIV Antibody Test (serum or plasma)
- Uni-Gold Recombigen HIV Test (whole blood, serum, plasma)
- Multispot HIV-1/HIV-2 Rapid Test (serum, plasma)
- INSTI HIV-1 Antibody Test
- Alere Determine HIV-1/2 Ag/Ab Combo Test (whole blood, serum, plasma)
- Clearview HIV 1/2 Ag/Ab Stat-Pak (whole blood, serum, plasma)
- Clearview Complete HIV 1/2 (whole blood, serum, plasma)
- HomeAccess HIV-1 Test System (drops of blood on a card that gets mailed to the lab)
- OraQuick In-Home HIV Test (oral fluid test for home use, results in as little as 20 minutes)
Rapid Oral HIV Pictures
HIV particles showing central core. Image courtesy of the Centers for Disease Control (CDC)/Edwin P. Ewing, Jr. OraQuick Advance Rapid HIV-1/2 Antibody Test. Photo courtesy of OraSure Technologies, 2004.