HIV Test after 40 days : which test to do

Published Date : 2023-09-11T20:54:05.696Z

Updated Date : 2023-09-11T20:54:05.696+00:00

How does the HIV virus multiply inside the body

Following exposure to the HIV virus, the virus initiates its replication cycle within submucosal cells. Upon meeting CD4 helper T cells, pivotal players in the immune system, the virus establishes contact. The virus's genetic material, manifested as viral RNA, infiltrates these CD4 cells. Through the action of reverse transcriptase, the viral RNA undergoes conversion into viral DNA. This viral DNA then orchestrates the cell's machinery to manufacture a higher volume of viral particles. Eventually, the infected cell's capacity is exceeded, causing it to rupture and release the generated virions into the bloodstream.

What viral particles are in the body around 40 days after exposure?

At 40 a large percentage of patients will show the presence of the viral RNA using molecular assays, IgM antibodies may no longer be detectable at this stage. Most patients should show detectable levels of IgG antibodies as well. The p24 antigen may no longer be detectable at this stage

The HIV Virus comprises of four detectable markers : HIV RNA, HIV P24 antigen, HIV IGM Antibodies and HIV IGG ANTIBODIES

What is a window period?

In HIV testing, the window period marks the interval before the immune system produces sufficient antibodies to trigger a positive test result.

Which are the different tests that can be done to detect HIV?

HIV detection involves the use of multiple testing methods, each specifically targeting different components of the virus. These methods include tests for the p24 antigen, antibodies such as IgM and IgG, and the highly sensitive RNA PCR tests.

Third Generation Tests

3rd generation tests are so called because they detect antibodies to the HIV 1 and HIV 2 strains. These tests are available in two formats - lab based automated assays, which automate the processes of pipetting and dispensing and point of care assays that can be done using standard manual pipetting.

Fourth Generation Tests

4th generation tests are so called because they detect both the HIV P24 antigen as well as antibodies to the HIV 1 and HIV 2 strains. These tests are available in two formats - lab based automated assays, which automate the processes of pipetting and dispensing and point of care assays that can be done using standard manual pipetting.

Will a 4th generation lab based test detect HIV at 40 days?

There is a good chance of a 4th generation lab based test being able to detect the virus in your body on day 40 after exposure to the HIV virus.

The 4th generation HIV test, a breakthrough in diagnostics, detects both the p24 antigen and IgM/IgG antibodies at the same time, aiding in early HIV identification..Lab based assays as described above are fully automated and are considered to be one of the most sensitive tests for early diagnosis of HIV. If you were exposed to HIV, there is a 92.9% chance that the 4th generation lab based assay will be able to detect the virus at 40 days. This is based on the varying levels of the p24 antigen as well as the time it takes for the antibodies to develop in the body agains the virus. It is recommended that you retest after some days since the chances of detecting HIV increase with time.

Will a 4th generation Point of Care based test detect HIV at 40 days?

There is a good chance of a 4th generation point of care based test being able to detect the virus in your body on day 40 after exposure to the HIV virus.

.Point of care assays as described above are generally performed with methods like lateral flow immunochromatography and are well suited for low resource and bedside settings. These assays have now achieved comparable results to lab based assays. If you were exposed to HIV, there is a 90.1% chance that a 4th generation point of care based assay will be able to detect the virus at 40. This is based on the varying levels of the p24 antigen as well as the time it takes for the antibodies to develop in the body agains the virus. It is recommended that you retest after some days since the chances of detecting HIV increase with time.

Will a third generation lab based assay detect HIV at 40 days?

There is a good chance of a 3rd generation lab based test being able to detect the virus in your body on day 40 after exposure to the HIV virus.

An established diagnostic approach, the 3rd generation HIV test detects both IgM and IgG antibodies against the virus, aiding in its timely identification..Third generation assay only test for the IgM and IgG antibodies, as such the latency for positivity with these assays is greater. Third generation lab based assays use automation in various steps of the test and as such are considered to be more accurate than the point of care tests, however they require more expensive equipment. If you were exposed to HIV, there is a 83.4% chance that a 3rd generation lab based assay will be able to detect the virus at 40 days. This is based on the time it takes for the antibodies to develop in the body agains the virus. It is recommended that you retest after some days since the chances of detecting HIV increase with time.

Will a third generation point of care based assay detect HIV at 40 days?

There is a relatively high chance of a 3rd generation point of care based test being able to detect the virus in your body on day 40 after exposure to the HIV virus.

.Third generation assay only test for the IgM and IgG antibodies, as such the latency for positivity with these assays is greater. Third generation point of care based assays use lateral flow chromatography or similar techniques and are suited for low resource settings. If you were exposed to HIV, there is a 66.5% chance, that a 3rd generation point of care based assay will be able to detect the virus at 40 days. This is based on the time it takes for the antibodies to develop in the body agains the virus. It is recommended that you retest after some days since the chances of detecting HIV increase with time.

Will a RNA PCR test detect HIV at 40 days?

There is a good chance of a RNA PCR Molecular Test being able to detect the virus in your body on day 40 after exposure to the HIV virus.

RNA PCR assays can detect viral loads as low as 20 copies of viral RNA/ml. RNA PCR assays can detect the virus as early as 10-12 days, and almost all patients will show positivity between 20-30 days.Based on the fact that you have been exposed 40 days ago, there is a 99.0% chance of the RNA PCR test being able to detect the virus.

What is the confirmatory test for HIV at 40?

There is no 100% confirmatory test for HIV. Any negative test is recommended to be repeated after 45-90 days. Positive tests are usually reconfirmed on repeated sampling in accordance with the guidelines of your country's health organizations. While the RNA PCR test usually has the highest chance of detecting the virus, it is never recommended as a first line test, owing to its cost and complexity. A first line screening test is usually done (4th generation) and if it is positive, additional testing is recommeded.

References

• Hurt CB, Nelson JAE, Hightow-Weidman LB, Miller WC. Selecting an HIV Test: A Narrative Review for Clinicians and Researchers. Sex Transm Dis. 2017 Dec;44(12):739-746. doi: 10.1097/OLQ.0000000000000719. PMID: 29140890; PMCID: PMC5718364.Hurt et,al
• Kevin P. Delaney and others, Time Until Emergence of HIV Test Reactivity Following Infection With HIV-1: Implications for Interpreting Test Results and Retesting After Exposure, Clinical Infectious Diseases, Volume 64, Issue 1, 1 January 2017, Pages 53–59,Delaney et.al