How Are Testing Technologies Used To Diagnose Hiv Infection
To test for HIV, a sample of a persons blood is taken. With the most common test, a vial of blood taken from a vein is sent to a laboratory to be tested for HIV . There are also rapid tests available, which use a drop of blood from a finger prick to test for HIV immediately after the sample is taken.
Why Do I Need An Hiv Test
The Centers for Disease Control and Prevention recommends that everyone between the ages of 13 and 64 get tested for HIV at least once as part of routine health care. You may also need an HIV test if you are at higher risk for infection. HIV is mainly spread through sexual contact and blood, so you may be at a higher risk for HIV if you:
- Are a man that has had sex with another man
- Have had sex with an HIV-infected partner
- Have had multiple sex partners
- Have injected drugs, such as heroin, or shared drug needles with someone else
HIV can spread from mother to child during birth and through breast milk, so if you are pregnant your doctor may order an HIV test. There are medicines you can take during pregnancy and delivery to greatly reduce your risk of spreading the disease to your baby.
When Is It Ordered
Several organizations recommend routine screening for HIV:
- The Centers for Disease Control , American College of Physicians , and the U.S. Preventive Services Task Force recommend that anyone between the ages of 13 and 64 and pregnant women be screened for HIV at least once.
- The CDC and American College of Obstetricians and Gynecologists recommend that all pregnant women be screened. Repeat testing in the third trimester may be done for women at high risk. A woman who wants to make sure she is not infected with HIV before getting pregnant may opt to get tested
- The American Academy of Pediatrics advises that all sexually active youth be screened, and that youths between 16 and 18 years old who live in high risk areas be offered HIV testing at least once, regardless of sexual history.
For additional details on screening recommendations, see the articles for Teens, Young Adults, Adults, and Adults 50 and Up.
Annual screening is advised for those at high risk for HIV and is recommended when an individual:
- Has had unprotected sex with more than one partner since the last HIV test
- Is a man who has had sex with another man
- Has used street drugs by injection, especially when sharing needles and/or other equipment
- Has exchanged sex for drugs or money
- Has an HIV-positive sex partner
- Has had sex with anyone who falls into one of the categories listed above or is uncertain about their sexual partner’s risk behaviors
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What If Your Hiv Test Result Is Negative
If your HIV test result is negative, it doesn’t necessarily mean you don’t have HIV. That’s because of the window periodthe time between when a person gets HIV and when a test can accurately detect it. The window period varies from person to person and depends on the type of HIV test you take.
Ask your health care provider or testing counselor about the window period for the type of HIV test youre taking. If youre using a self-test, you can find that information in the test package.
If your test result is negative,get tested again after the window period to be sure. If your test result is negative again, and you have had no possible HIV exposure during the window period, then you do not have HIV.
Whats next? Now is a good time to think about your HIV prevention options. If youre sexually active or use needles to inject drugs, continue to take actions to prevent HIV, like taking pre-exposure prophylaxis, or PrEP if youre at high risk or using condoms the right way every time you have sex.
If you have certain risk factors for HIV, you should continue to get tested at least once a year. Learn more about who is at risk for HIV and why they should be tested more often.
Understanding The Testing Window
HIV tests work by checking a persons blood or saliva for antigens or antibodies. However, these antigens/antibodies take time to multiply and show up on a test. Therefore, if a person tests too early, their tests results will not be accurate. The testing window varies deepening on the test. However, most tests cannot detect the infection until 18+ days after exposure.
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What To Do If Youve Been Exposed
If youve been exposed to HIV, go to a hospital or clinic immediately. If you are HIV-negative, then there are emergency medications that you may be able to take in order to prevent infection. While taking these medications, you will need to avoid certain activities, such as breastfeeding or having unprotected sex. Be sure to follow the doctors exact instructions, and always ask for clarity if you have any questions.
Furthermore, the hospital or clinic will help you determine the best time to get tested after your exposure. Share as much information as you can with medical professionals in order to get the best advice.
What Do The Results Mean
If your result is negative, it can mean you don’t have HIV. A negative result may also mean you have HIV but it’s too soon to tell. It can take a few weeks for HIV antibodies and antigens to show up in your body. If your result is negative, your health care provider may order additional HIV tests at a later date.
If your result is positive, you will get a follow-up test to confirm the diagnosis. If both tests are positive, it means you have HIV. It does not mean you have AIDS. While there is no cure for HIV, the disease can be effectively controlled with medicine. The medicine used to treat HIV is called antiretroviral therapy . ART can significantly reduce the amount of HIV in the blood. People with HIV who take ART before the disease gets too advanced can live long, healthy lives. If you are living with HIV, it’s important to see your health care provider regularly.
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Hiv Tests Used In British Columbia
These tests measure antibodies to HIV. Antibodies are proteins made by the immune system when the body is exposed to an infection. It takes time for the body to make antibodies after it is exposed to HIV, and different people make antibodies at different rates.
The window period for antibody tests is between 3 weeks and 3 months. Up to 95% of people will have antibodies after 6 weeks, and 99% of people will have antibodies after 3 months.
The point-of-care HIV test is an antibody tests offered in some locations in BC. The HIV Confirmatory Assay is an antibody test used to confirm a preliminary positive HIV result.
The 4th generation Enzyme Immunoassay Test test is a combined antigen / antibody test. The antigen, or viral protein, used to detect HIV is called p24 antigen. This p24 antigen shows up in the blood soon after a person gets HIV.
The 4th generation EIA test is the standard HIV laboratory screening test used in BC. Ninety-nine percent of these tests will be positive 6 weeks after a person gets HIV.
This test looks for the genetic material of HIV in the blood. It is also known as the “early HIV test” or “RNA test”. Ninety percent of NAATs are positive 10 to 12 days after a person gets HIV, and over 99% are positive after 6 weeks.
The RNA NAAT can be specially ordered by doctors or nurses if someone has had a recent high-risk exposure to HIV and/or they are having symptoms that are highly indicative of HIV.
Which Test Is Which
Figure 11 lists commonly used HIV tests and shows what type of test they are.
Your testing centre should tell you this information for the test that they use.
Sometimes testing centres give the tests explained above different names like ELISA or Western blot without explaining what kind of test they are and what it is they are looking for.
ELI, MEIA, ELFA, ECLIA use similar technology to ELISA tests.
UK guidelines recommend using 4th generation tests but 5% of clinics still use 3rd generation tests.
Ask your clinic for more detailed information about the type of test that they use.
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How Is It Used
HIV antibody and HIV antigen testing is used to screen for and diagnose HIV infections. Early detection and treatment of HIV infection and immune system monitoring can greatly improve long-term health and survival. Also, if a person knows his or her HIV status, it may help change behaviors that can put him or her and others at risk.
Different types of tests may be used for HIV screening:
There are a few different ways a person can get access to HIV screening:
To Facilitate Hiv Testing Healthcare Providers Can:
- normalise the offer of HIV testing, making it part of routine care
- assure protection of the persons anonymity and confidentiality
- offer an environment that is free of stigma and discrimination
- emphasize the benefits of early diagnosis and treatment
- provide information on risk factors for HIV infection, and prevention methods
- discuss testing options, including POC testing and self-testing
- when taking a sexual health history, keep it brief and relevant, as detailed risk assessments can deter people from seeking care
HIV self-testing and POC testing can facilitate uptake of screening. In addition, HIV self-testing provides an option for people who face barriers to accessing testing in healthcare settings.
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There Are Three Main Tests:
- Fourth Generation: The 4th generation test, is a type of blood test which takes about 3-5 days to get the results. This test is sensitive enough to detect HIV in your blood 2 weeks after a possible exposure. Offered almost everywhere.
- Rapid test :Both tests take about 20 minutes to get the results. This test will provide you with results 6 to 8 weeks after an exposure.
- Blood test is a finger stick a small amount of blood is taken from the tip of the finger and mixed in a solution. There are both 4th and 3rd generation rapid tests.
- Oral test a small amount of saliva from a persons mouth is obtained using a cotton swab that looks like a toothbrush. You can buy this test at a pharmacy. We strongly encourage people to get tested in a clinic or at your primary care providers office for additional support and education.
If any preliminary test is positive, the NAT blood test is done to confirm that the person is HIV positive.
Its important to know there are three types of results that can come from a rapid test: invalid, non-reactive and reactive.
The third and last part of testing is getting your results and talking about what those results mean for the future. No matter which test a person chooses to do, its very important to always get your results!
People Are At Risk And Need To Test Hiv Every Year Are Following
- People who have several sexual partners
- Performed sexual intercourse with somebody who is infected by HIV or at a potential risk zone.
- Someone whose sexual history is unknown or doubtful
- Drugs were injected using a needle, syringe, or other devices that had previously been used by someone else.
- Tested positive for TB, Herpes, Syphilis or/and any STDs
- Performed sexual intercourse with somebody who has STDs.
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What Should I Expect When I Get Tested
I Just Read Your Guide On Hiv Testing And It Mentions A Reactive Result Is Considered A Preliminary Positive And Means That Hiv Antibodies Were Found So What Does It Mean If The Second Test Is Negative
Human immunodeficiency virus is a virus that attacks the bodys immune system. If HIV isnt treated it can progress into acquired immunodeficiency syndrome . However, with early testing and proper medical care its unlikely that HIV will progress into AIDS. Anyone who has unprotected sex and or shares needles or injection drug equipment is at an increased risk for developing HIV/AIDS. The virus is spread through contact with infected blood, semen, vaginal fluid, and or breast milk. The best way to prevent transmission of HIV always use a condom, this will also help prevent pregnancy and sexually transmitted infections .
There are three different ways you can be tested for HIV fourth generation blood test, rapid test , and confirmatory test nucleic acid testing . The test you are asking about is the rapid test, which takes about 20 minutes to get results, but it will only show accurate results 6 to 8 weeks after exposure. The rapid test can give three different results: invalid, non-reactive, and reactive. A reactive result means exactly what you said it is considered a preliminary positive and means that HIV antibodies were found. If this occurs, a second confirmatory test needs to be performed. If the NAT test results as negative, it is likely that you will need another test to confirm your results. If you are concerned that you have contracted HIV or AIDS, schedule an appointment with your health care provider to receive HIV testing, immediately.
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Hiv Antibody Enzyme Immunoassay
Because of its rapidity, sensitivity and low cost, the enzyme immunoassay is the standard screening tool for HIV infection. Synthetic and native HIV antigens, xed on a solid phase, are exposed to and bound by HIV antibodies in test serum. These antibodies are then detected by a second antibody to human IgG, with a sensitivity of more than 99.5%. Most commercially available EIAs are automated and allow for high throughput testing. For example, most laboratories in Australia use testing instrument platforms that enable continuous loading of specimens with results being available within 1 hour. The EIA also detects antibodies against a broad range of HIV types and subtypes, and is continually updated to include newly described HIV-1 subtypes.
The weeks between HIV infection and seropositivity are termed the window period and are associated with high levels of circulating HIV RNA, and potentially more ecient HIV transmission. Direct detection of HIV nucleic acids by molecular amplification tests such as polymerase chain reaction or serological detection of HIV p24 antigen is usually possible before the detection of HIV antibodies. These direct detection virological tests are indicated in suspected cases of primary infection or seroconversion illness or having a high-risk exposure in the previous 6 weeks and suspected of having acute HIV infection.
Appendix : Different Types Of Hiv Test
Different HIV tests work by looking for three different things.
In this section we describe the main HIV tests.
- Antigen only . These are rarely used.
- Antibody only tests . These are rarely used because of more recent availablilty of joint Ag/Ab tests.
- Combined antibody-antigen tests. These are the most commonly recommended tests in the UK. these test for p24 plus antibodies.
- Viral load tests
More details about how the tests work and the science behind them is included in Appendix 3.
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