Hiv Testing Types And Lab Technologies
This chapter provides information regarding available testing technologies, approaches to testing and interpretation of results. There are many different types of HIV screening tests that are licensed for use in Canada and can vary by jurisdiction. For questions or information specific to your province or territory please contact your local Public Health laboratory.
How Do The Tests Work
Most HIV tests use a blood sample, either from a blood draw or finger prick. Others use saliva , but this is a little less accurate than blood tests.
Some HIV tests look for the virus itself. But most look for the antibodies for HIV. Antibodies are part of the immune system and fight infections. When someone is infected with HIV, the body creates antibodies to fight HIV.
Testing results may be available that day or can take longer come back.
Other Factors Influencing Hiv Transmission Risk
Within each route of transmission, estimates of the risk of transmission vary widely, likely due to the role of behavioural and biological co-factors. Viral load appears to be an important predictor of transmission, regardless of route of transmission. However, the evidence indicates that viral load is not the only determinant, and other co-factors, such as the presence of co-infections, play a role in increasing or decreasing the risk of transmission.
Viral Load
The strongest predictor of sexual transmission of HIV is plasma viral load . A dose-response relationship has been observed, where each ten-fold increase in plasma VL resulted in an increased relative risk of transmission of 2.5 to 2.9 per sexual contact. The concentration of HIV in genital secretions also plays a major role in sexual transmission. While there is a strong correlation between HIV concentrations in plasma and in genital secretions, some studies have found genital tract HIV shedding in 20% to 30% of men and women without detectable plasma viral load. Much of what is known about the impact of viral load on the sexual transmission of HIV is derived from studies of heterosexual populations. Very little is known about the relationship between HIV viral load and rate of transmission through anal intercourse.
Co-infections
Circumcision
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Types Of Hiv Testing Services
4.5.1 Standard
The majority of healthcare venues carry out “standard” HIV testing. This means a tube of blood is collected in the clinic, hospital or physician’s office and sent to the medical laboratory along with a requisition ordering an HIV test. Standard testing can be done in any type of setting . Test results are generally available within one week.
4.5.2 Point-of-Care or rapid testing
Stage : Clinical Latency
In this stage, the virus still multiplies, but at very low levels. People in this stage may not feel sick or have any symptoms. This stage is also called chronic HIV infection.
Without HIV treatment, people can stay in this stage for 10 or 15 years, but some move through this stage faster.
If you take HIV medicine every day, exactly as prescribed and get and keep an undetectable viral load, you can protect your health and have effectively no risk of transmitting HIV to your sexual partner.
But if your viral load is detectable, you can transmit HIV during this stage, even when you have no symptoms. Its important to see your health care provider regularly to get your viral load checked.
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Automatic Partner Notification Of Sponsored Family Class Applicants Who Test Positive For Hiv
Applicants in the family class and the dependent refugee class who test positive for HIV may not be assessed as medically inadmissible due to excessive demand on Canadas health care system . Their sexual partners residing in Canada must be made aware of the risk this serious medical condition may place on their health.
Automatic partner notification will give applicants in the family and dependant refugee classes who test positive for HIV 60 days from the date of being informed of the policy to voluntarily disclose their HIV-positive status to their spouse or partner or to withdraw their application. After this period, the Department will formally notify the spouse or partner of their dependants HIV-positive status before proceeding with the application.
To facilitate Immigration, Refugees and Citizenship Canada s commitment toward public health and safety, this policy provides HIV-positive applicants with an appropriate window of opportunity to voluntarily disclose their medical status or withdraw their application.
Medical officers will continue to notify immigration program managers of cases where individuals test positive for HIV in both the family class and dependant refugee class. Although these cases are few, it is important that these instructions be followed accurately.
Where To Access Testing Services
Standard HIV testing can generally be accessed through any health provider across the country. Each province is responsible for licensing the laboratories that provide HIV screening and confirmatory testing in its jurisdiction. In general, all provincial Public Health Laboratories provide both screening and confirmatory testing. Reference and specialized services, when required, are provided by the National HIV Reference Serology Laboratory after consultation with the provincial laboratory. It is advisable to contact your testing laboratory to confirm the specimen collection details.
Anonymous or POC testing locations can be found by calling a local HIV/AIDS hotline .
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Types Of Hiv Tests And Their Window Periods
- Nucleic Acid Test A NAT can usually tell you if you have HIV infection 10 to 33 days after exposure
- Antigen/Antibody TestAn antigen/antibody test performed by a laboratory on blood from a vein can usually detect HIV infection 18 to 45 days after exposure. Antigen/antibody tests done with blood from a finger prick take longer to detect HIV .
- Antibody TestAn antibody test can take 23 to 90 days to detect HIV infection after an exposure. Most rapid tests and self-tests are antibody tests. In general, antibody tests that use blood from a vein detect HIV sooner after infection than tests done with blood from a finger prick or with oral fluid.
Ask your health care provider or test counselor about the window period for the test youre taking and whether you will need a follow-up test to confirm the results. If youre using a self-test, you can get that information from the materials included in the tests package.
If you get an HIV test after a potential HIV exposure and the result is negative, get tested again after the window period. Remember, you can only be sure you are HIV-negative if:.
- Your most recent test is after the window period
- You havent had a potential HIV exposure during the window period. If you do have an exposure, then you will need to be retested.
Sharing Your Test Result
Will other people know my test result?
If you take an anonymous test, no one but you will know the result. If you take a confidential test, your test result will be part of your medical record and it is protected by state and federal privacy laws.
Anonymous testing means that nothing ties your test results to you. When you take an anonymous HIV test, you get a unique identifier that allows you to get your test results. You can also purchase a self-test if you want to test anonymously.
Confidential testing means that your name and other identifying information will be attached to your test results. The results will go in your medical record and may be shared with your health care providers and your health insurance company. Otherwise, the results are protected by state and federal privacy laws, and they can be released only with your permission.
With confidential testing, if you test positive for HIV, the test result and your name will be reported to the state or local health department to help public health officials get better estimates of the rates of HIV in the state. The state health department will then remove all personal information about you and share the remaining non-identifying information with CDC. CDC does not share this information with anyone else, including insurance companies.
For more information, see HIV.govs questions about civil rights, legal disclosure, insurance, and the workplaceexternal icon.
Should I share my positive test result with others?
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If I Test Positive For Hiv What Follow
If you are HIV-positive, follow-up tests may include the following:
- HIV viral load testingmeasures the amount of HIV in the blood. It is performed when you are first diagnosed to help determine the status of the disease and is ordered at intervals to monitor the effectiveness of therapy.
- CD4 countmeasures the number of CD4 T-cells in the blood. It is ordered when you are first diagnosed to get a baseline assessment of your immune system and it is done at intervals to monitor therapy and the status of the immune system.
- HIV antiretroviral drug resistance testing, genotypicordered when you are initially diagnosed to determine whether the particular strain of HIV that you have is resistant to certain antiretroviral drug therapies. This testing is also ordered when treatment is changed or when there is evidence of treatment failure.
How Does Hiv Testing Work
In the early stages of HIV infection, the virus itself is difficult to detect. Rather than looking for the virus, HIV testing usually involves looking at the body’s reaction to the presence of the virus. The measure of the amount of virus in an individual’s blood stream is called the viral load.
Antibodies are produced by the body in reaction to the presence of a virus. An HIV antibody test measures the presence of antibodies in response to the presence of HIV. The most common HIV antibody tests are ELISA and Western Blot. These tests can now be performed on samples of oral fluid.
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Dried Blood Spot Test
A DBS test is a free, accurate and convenient way to test for HIV in the comfort and privacy of your home.
It involves collecting a few drops of blood from your finger and allowing the blood to dry on a test card. You then send the card away to get tested and wait around a week to get the result back. You can register for a DBS HIV test here.
Does Being Durably Undetectable Mean That The Virus Has Left My Body
Even when viral load is undetectable, HIV is still present in the body. The virus lies dormant inside a small number of cells in the body called viral reservoirs. When therapy is halted by missing doses, taking a treatment holiday or stopping treatment, the virus emerges and begins to multiply, becoming detectable in the blood again. This newly reproducing virus is infectious. It is essential to take every pill every day as directed to achieve and maintain a durably undetectable status.
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A Word About Window Periods
The window period refers to the time it takes for HIV to show up in an HIV test. The length of the window period will depend on the type of test you take.
If you feel like you may be at risk of HIV, do not wait, speak to a healthcare professional as soon as possible. The most important thing is to test.
If you test negative but think you may have been exposed to HIV more recently, you can take another test once the window period has passed.
The picture below shows the window periods for different HIV tests. Some tests can give you an accurate result within four weeks, while others can take three months to be accurate .
A healthcare worker will be able to explain how long the window period is for the test you are taking, and will tell you if they think youll need to test for HIV again.
How Confidential Are Hiv Test Results
Your HIV status, like other medical conditions and test results, is protected by the HIPAA Privacy Rule and cannot be shared with friends, family, or employers without your written permission. Your HIV status may be shared with your healthcare providers who have a “need to know” in order to treat you. Also, in order to determine the incidence of HIV and to provide appropriate prevention and care services, all new cases of HIV are reported to state and local health departments.
Certain testing centers provide either anonymous or confidential HIV testing and counseling. You can also contact your state or local health department to find out where testing may be available.
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Informed Consent For Testing
In Ontario, there are two ways to get tested for HIV: nominal testing and anonymous testing. You must give informed consent before being tested, whether the test is done nominally or anonymously. Informed consent means that you:
- understand the procedures and the consequences of being tested, including Public Health reporting requirements
- receive pre-test and post-test counselling to prepare for the test and test result and,
- give your permission to be tested.
If someone tests you for HIV without your informed consent, you may want to get legal advice.
Introduction And Guiding Principles
A request was made by the Federal/Provincial/Territorial Committee on AIDS for the Public Health Agency of Canada to develop guidelines on HIV testing that reflect the realities facing care providers and their clients, as well as advances in HIV testing policy and practice. To inform the development of this guide, the Agency commissioned a literature review and consultations with key stakeholders, including people living with HIV/AIDS and other affected populations, academics, nurses, physicians, professional associations, non-governmental organizations, policy-makers, community workers, and legal and ethical experts. As a result, the recommendations outlined in the guide are based on the most up-to-date evidence and expert opinion.
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General Overview Of The Policy
All permanent resident applicants who are 15 years of age or older, as well as children who have certain risk factors, such as having received blood or blood products, having a known HIV-positive mother or being potential adoptees are required to undergo an HIV test as part of the medical examination.
As part of this medical examination, the responsible panel physician will provide post-test counselling to HIV-positive applicants as per the guide for designated medical practitioners. The panel physician will have the applicant sign the Acknowledgement of HIV post-test counselling form .
Applicants will then be required to attend an interview with a visa or immigration officer, where they will be informed of the Automatic partner notification policy for HIV-positive applicants in the family and dependant refugee classes and will be asked to sign the Acknowledgment of the automatic partner notification policy for HIV-positive applicants in the family and dependant refugee classes to indicate theyve been informed of this policy. The officer should be satisfied that the applicant has understood the implications and been informed of the policy and should address any concerns the applicant may have with regard to their application.
The visa or immigration officer will then give the applicant 60 days to disclose their HIV-positive status to their spouse or partner residing in Canada or withdraw their application.
What Is An Hiv Test
An HIV test shows whether you are infected with HIV . HIV is a virus that attacks and destroys cells in the immune system. These cells protect your body against disease-causing germs, such as bacteria and viruses. If you lose too many immune cells, your body will have trouble fighting off infections and other diseases.
There are three main types of HIV tests:
- Antibody Test. This test looks for HIV antibodies in your blood or saliva. Your immune system makes antibodies when you are exposed to bacteria or viruses, like HIV. An HIV antibody test can determine if you have HIV from 312 weeks after infection. That’s because it can take a few weeks or longer for your immune system to make antibodies to HIV. You may be able to do an HIV antibody test in the privacy of your home. Ask your health care provider about at-home HIV test kits.
- HIV Antibody/Antigen Test. This test looks for HIV antibodies and antigens in the blood. An antigen is a part of a virus that triggers an immune response. If you’ve been exposed to HIV, antigens will show up in your blood before HIV antibodies are made. This test can usually find HIV within 26 weeks of infection. The HIV antibody/antigen test is one of the most common types of HIV tests.
- HIV Viral Load. This test measures the amount of the HIV virus in the blood. It can find HIV faster than antibody and antibody/antigen tests, but it is very expensive. It is mostly used for monitoring HIV infections.
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What Does A Negative Hiv Test Result Mean
A negative result doesn’t necessarily mean that 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 is also different depending upon the type of HIV test.
Ask your health care provider about the window period for the kind of test youre taking. If youre using a home test, you can get that information from the materials included in the tests package. If you get an HIV test after a potential HIV exposure and the result is negative, get tested again after the window period for the test youre using to be sure. To learn more about the window period and when a person should get retested, see CDCs How soon after an exposure to HIV can an HIV test if I am infected?. If you get an HIV test within 3 months after a potential HIV exposure and the result is negative, get tested again in 3 more months to be sure.
If you learned you were HIV-negative the last time you were tested, you can only be sure youre still negative if you havent had a potential HIV exposure since your last test. If youre sexually active, continue to take actions to prevent HIV, like using condoms the right way every time you have sex and taking medicines to prevent HIV if youre at high risk.