Reflex Pathway for the HIV-1/2 Antigen and Antibodies, Fourth Generation, with Reflexes Assay
Reflex Pathway for the HIV-1/2 Antigen and Antibodies, Fourth Generation, with Reflexes Assay
This algorithm depicts the reflex path for the HIV-1/2 Antigen and Antibodies, Fourth Generation, With Reflexes assay.
This algorithm depicts the reflex path for the HIV-1/2 Antigen and Antibodies, Fourth Generation, With Reflexes assay.
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HIV-1/2 Antigen and Antibodies, Fourth Generation, with Reflexes
This algorithm is used to help diagnose HIV-1 and HIV-2 infection, including acute infection, and to differentiate HIV-1 from HIV-2. It is consistent with the HIV diagnostic algorithm recommended by the Centers for Disease Control and Prevention [2]. It can be used in adults, including pregnant women, and in children 2 years or older.
This panel begins with an antigen/antibody assay that allows for detection of acute HIV-1 infection based on the presence of p24 antigen before seroconversion occurs, and HIV-1 and HIV-2 antibodies post-seroconversion. If the HIV-1/HIV-2 antigen/antibody test is positive, an antibody-differentiation test is done (at additional charge) to confirm infection and identify the presence of HIV-1 or HIV-2 specific antibodies. However, the HIV-1/HIV-2 differentiation test can be negative during acute infection (prior to development of specific antibodies). If the antibody-based HIV-1/HIV-2 supplemental test is negative, the specimen will be reflexed to the HIV-1 and HIV-2 RNA, Qualitative, Real-Time PCR test (at additional charge), which can detect the presence of HIV-1 and 2 RNA and identify patients with acute HIV-1 or 2 infection [1].
The United States Preventive Services Task Force (USPSTF) recommends HIV screening for all pregnant women, and for individuals between 15 and 65 years of age who live in regions with an HIV prevalence of >0.1% [2]. In addition, antigen/antibody-based HIV testing is recommended for high-risk individuals who want to begin pre-exposure prophylaxis (PrEP) therapy, because HIV-positive patients who start PrEP without knowing their HIV status face an elevated risk of antiretroviral resistance [3,4].
Because 40% of new HIV infections are transmitted unknowingly by people unaware of their HIV status, early diagnosis is important to reduce HIV transmission [5]. Antigen/antibody-based HIV screening assays have >99.7% sensitivity and >99.3% specificity for HIV infection and can identify most (>80%) acute infections that would otherwise require nucleic acid testing for detection [6,7].
References
1. Moyer V, USPTF. Ann Intern Med. 2013;159:51-60.
2. CDC. Clinical Testing Guidance for HIV. Clinical Testing Guidance for HIV | HIV Nexus | CDC. Published September 10, 2024. Accessed January 27, 2025.
3. CDC. Preventing HIV with PrEP. https://www.cdc.gov/hiv/prevention/prep.html?CDC_AAref_Val=https://www.cdc.gov/hiv/basics/prep.html. Published January 18, 2024. Accessed January 27, 2025.
4. Livant E, et al. J Clin Virol. 2017;94:15-21.
5. CDC. HIV testing. https://www.cdc.gov/hiv/testing/index.html. Published March 2019. Accessed May 20, 2019.
6. Nasrullah M, et al. AIDS. 2013;27:731-737.
7. Chavez P, et al. J Clin Virol. 2011;52(Suppl 1):S51-S55.
This panel begins with an antigen/antibody assay that allows for detection of acute HIV-1 infection based on the presence of p24 antigen before seroconversion occurs, and HIV-1 and HIV-2 antibodies post-seroconversion. If the HIV-1/HIV-2 antigen/antibody test is positive, an antibody-differentiation test is done (at additional charge) to confirm infection and identify the presence of HIV-1 or HIV-2 specific antibodies. However, the HIV-1/HIV-2 differentiation test can be negative during acute infection (prior to development of specific antibodies). If the antibody-based HIV-1/HIV-2 supplemental test is negative, the specimen will be reflexed to the HIV-1 and HIV-2 RNA, Qualitative, Real-Time PCR test (at additional charge), which can detect the presence of HIV-1 and 2 RNA and identify patients with acute HIV-1 or 2 infection [1].
The United States Preventive Services Task Force (USPSTF) recommends HIV screening for all pregnant women, and for individuals between 15 and 65 years of age who live in regions with an HIV prevalence of >0.1% [2]. In addition, antigen/antibody-based HIV testing is recommended for high-risk individuals who want to begin pre-exposure prophylaxis (PrEP) therapy, because HIV-positive patients who start PrEP without knowing their HIV status face an elevated risk of antiretroviral resistance [3,4].
Because 40% of new HIV infections are transmitted unknowingly by people unaware of their HIV status, early diagnosis is important to reduce HIV transmission [5]. Antigen/antibody-based HIV screening assays have >99.7% sensitivity and >99.3% specificity for HIV infection and can identify most (>80%) acute infections that would otherwise require nucleic acid testing for detection [6,7].
References
1. Moyer V, USPTF. Ann Intern Med. 2013;159:51-60.
2. CDC. Clinical Testing Guidance for HIV. Clinical Testing Guidance for HIV | HIV Nexus | CDC. Published September 10, 2024. Accessed January 27, 2025.
3. CDC. Preventing HIV with PrEP. https://www.cdc.gov/hiv/prevention/prep.html?CDC_AAref_Val=https://www.cdc.gov/hiv/basics/prep.html. Published January 18, 2024. Accessed January 27, 2025.
4. Livant E, et al. J Clin Virol. 2017;94:15-21.
5. CDC. HIV testing. https://www.cdc.gov/hiv/testing/index.html. Published March 2019. Accessed May 20, 2019.
6. Nasrullah M, et al. AIDS. 2013;27:731-737.
7. Chavez P, et al. J Clin Virol. 2011;52(Suppl 1):S51-S55.
Reference ranges are provided as general guidance only. To interpret test results use the reference range in the laboratory report.
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