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Infectious Disease
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Susanna J. Dunachie, Hanif Esmail, Ruth Corrigan, Maria Dudareva
HIV serology testing combines enzyme-linked immunosorbent assays for antibodies against HIV-1, HIV-2, and viral p24 antigen. This is highly sensitive and specific, with a false negative ‘window period’ of around 10 days in primary HIV infection.
Pharmacologic alternatives to blood
Published in Jennifer Duguid, Lawrence Tim Goodnough, Michael J. Desmond, Transfusion Medicine in Practice, 2020
The US blood supply is the safest it has ever been, owing to the evolution of a combination of donor education, donor screening, and new laboratory test procedures. Risks of transfusion-transmitted viral infections are extremely low – estimated in 1996 to be approximately one in 650 000 units for human immunodeficiency virus (HIV), one in 100 000 for hepatitis C virus (HCV), and one in 60 000 for hepatitis B virus (HBV).1 More rigorous pre-donation screening has led to a rapid decline in prevalence of HIV and HCV in first-time blood donors at five US blood centers,2 with HIV decreasing from 0.03% (1991–1992) to 0.02% (1993–1996) and HCV decreasing from 0.63% (1992) to 0.40% (1996), despite an increase in prevalence in the general population for both HIV (0.3% in 1992) and HCV (1.8% in 1988–1994). In 1999, introduction of nucleic acid amplification testing (NAT) for HIV and HCV further reduced the window period, which is the time between a potential blood donor infection and detectability by screening tests at time of donation, by 30–50%. The most significant risk of mortality from blood transfusion is now believed to be administrative error1 resulting in an ABO mismatch between blood unit and transfusion recipient, with hemolysis (1 in 60 000) and death (1 in 600 000).
The Immune System During HIV-1 Infection
Published in Niel T. Constantine, Johnny D. Callahan, Douglas M. Watts, Retroviral Testing, 2020
Niel T. Constantine, Johnny D. Callahan, Douglas M. Watts
The appearance of p24 antigen in the serum (antigenemia) very early after infection is also to be noted. Although this may occur, the quantities of antigen may be very low, and may not be detected by antigen assay methods (Chapter 4). The period after infection has occurred but before antibody can be demonstrated (generally 0 to 6 weeks), is called the “window period”. It is during this window period that a test for antibody will be negative, although the individual is indeed infected. Therefore, the antibody test will produce a false-negative result.
Highlighting and addressing barriers to widespread adaptation of HIV self-testing in the United States
Published in Expert Review of Molecular Diagnostics, 2023
The United States has a single second-generation oral fluid test, which detects only IgG antibodies [33]. Third-generation tests, which detect both IgM and IgG responses, have a shorter ‘window period’ after acute infection when serologic tests may be falsely negative as a serologic response has not yet occurred. Both the WHO and European Union have approved third-generation tests (Table 1). Although oral HIV self-tests are preferred due to their ease of collection of samples, their slightly lower sensitivity due to lower and more variable concentration of antibodies in the oral fluid may also result in a larger ‘window period’ of non-detection [33,51]. More research will need to be done to increase acceptability of blood-based self-tests or improve alternative detection methods using oral fluid, but the majority of tests preapproved by the WHO have been fingerstick blood.
Three-year outcome of rapid HIV testing at public health centers in Seoul, Republic of Korea: a short report
Published in AIDS Care, 2021
Hye-Jin Yang, Jungmee Kim, Ji Hwan Bang, Cho Ryork Kang, Sung-Il Cho, Myoung-don Oh, Eung Soo Hwang, Jong-Koo Lee
This study had some limitations. First, because the rapid HIV screening tests are conducted anonymously, some examinees may have been tested more than once, making it impossible to determine the actual number or characteristics of people who took the tests in screening stage by the rapid HIV test. But, if a person has been confirmed HIV infection by western blot, he (or she) has been checked the personal information and got a control number. Thus, there has been no possibility of duplication in the number of confirmed cases. Second, the window period of the rapid HIV screening test is longer (about 10 days) than that of the fourth-generation ELISA test. For this reason, our dataset could include false negative results for people in the earliest stages of HIV infection. However, all the examinees have been repeatedly announced on the window period and recommend to consult to a specialist if there has been possibility of early infection. Thus, we think there have been few, if any, false negative results related to window period.
Stuck in the window with you: HIV exposure prophylaxis in the highest risk people who inject drugs
Published in Substance Abuse, 2019
Jessica L. Taylor, Alexander Y. Walley, Angela R. Bazzi
In order to mitigate the risk of viral resistance, guidelines require a negative HIV test before patients start PrEP.10 Added caution is required for patients who have had signs or symptoms of acute HIV, which include night sweats, diarrhea, and myalgias – symptoms that overlap with typical opioid withdrawal – in the past month. In these cases, the CDC outline three options: (1) document a negative HIV antigen/antibody (Ag/Ab) test and start PrEP immediately, (2) document a negative HIV RNA viral load and start PrEP immediately, and (3) defer PrEP decision and repeat testing in 1 month.10 Amidst current HIV outbreaks, a month is too long to wait. However, the first two options may not offer adequate reassurance for those with recent, high-risk exposures due to the HIV testing “window period,” the time between infection and test positivity. The window period is estimated to be 10–15 days for HIV RNA and 15–20 days for HIV Ag/Ab tests.13 If a patient presents, for example, four days after receptive syringe sharing, we would need to wait 6 more days until a negative HIV RNA test could be considered reliable, assuming they accrue no further exposures (Figure 1).