What is the conclusiveness of a negative HIV 1/2 test result using the Abbott Determine (HIV 1/2 antibody test) at 107 days post-exposure and 30 days post-antiretroviral Post-Exposure Prophylaxis (PEP) (emtricitabine/tenofovir disoproxil fumarate) in a patient with high-risk exposure to HIV?

From the Guidelines

The Abbott Determine HIV 1/2 test result at 107 days post-exposure (30 days after completing PEP) is highly conclusive, strongly suggesting the patient did not contract HIV from the exposure. This negative result is highly reliable, given that the test is over 99% accurate after 3 months post-exposure, which this patient has exceeded 1. The Post-Exposure Prophylaxis (PEP) the patient took, though started later than the recommended 72-hour window, may have still provided some protective benefit, as indicated by guidelines for the management of occupational exposures to HIV and recommendations for postexposure prophylaxis 1.

Key Considerations

• HIV antibody tests detect the body's immune response to the virus, which typically develops within 3 months of infection in virtually all patients, making this negative result highly reliable 1.
• While no test is 100% definitive, the chance of turning positive after a negative result at this point is extremely low, with rare instances of delayed HIV seroconversion reported 1.
• For complete reassurance, the patient could consider one final confirmatory test at 6 months post-exposure, though many experts now consider the 3-month window sufficient for conclusive results.

Recommendations

• The patient's negative test result at 107 days post-exposure can be considered conclusive, given the high accuracy of the test after 3 months post-exposure.
• A final confirmatory test at 6 months post-exposure may be considered for complete reassurance, but is not necessarily required.
• The patient should continue to practice safe behaviors to prevent future exposures to HIV.

From the Research

HIV Testing and Post-Exposure Prophylaxis (PEP)

• The conclusiveness of a negative HIV 1/2 test result using the Abbott Determine (HIV 1/2 antibody test) at 107 days post-exposure and 30 days post-antiretroviral PEP (emtricitabine/tenofovir disoproxil fumarate) in a patient with high-risk exposure to HIV is uncertain due to the potential for false-negative results in the presence of antiretroviral therapy (ART) for PEP 2.
• HIV-specific antibody point-of-care tests (POCT), such as the Abbott Determine, may not detect acute HIV infection, which can lead to delayed or absent development of HIV-specific antibodies, posing a diagnostic challenge 2.
• The use of ART for PEP can suppress HIV RNA viral load, complicating current HIV testing algorithms and potentially leading to false-negative results 2.

Diagnostic Challenges and Testing Algorithms

• The World Health Organisation (WHO) recommends a testing strategy that includes the use of HIV-specific antibody POCT, but these tests may not detect acute HIV infection 2.
• Alternative HIV testing algorithms, such as viral load detection, may be needed to mitigate diagnostic dilemmas in the setting of increased utilization of ART for immediate treatment and prevention of HIV infection 2.
• Research and surveillance are needed to determine the most appropriate assays and optimal testing algorithms that are accurate, affordable, and sustainable 2.

Post-Exposure Prophylaxis (PEP) and HIV Testing

• PEP is effective in preventing illness after potential or documented exposure to HIV, but guidelines recommend baseline testing for HIV antibodies and follow-up testing at six weeks, three months, and six months postexposure 3.
• The timing and severity of illness in the source patient, the exposed person's susceptibility to infectious diseases of concern, and the relative risks and benefits of the PEP regimen should be assessed when determining the need for PEP 3.