Accuracy of the 4th Generation HIV Test at 28 Days

The 4th generation HIV test, often referred to as a combination test, checks for both HIV antibodies and p24 antigen. A common concern with HIV testing is the window period, where the body has not yet developed detectable antibodies. At 28 days post-exposure, a 4th generation HIV test is generally considered to be quite accurate, with sensitivity rates typically around 95% or higher.

However, it's important to note that while a negative result at 28 days serves as a strong indicator that a person is not infected, it is still recommended to follow up with another test at 3 months for a definitive result. This is because some individuals may take longer to develop detectable antibodies, and the window period can vary. Consulting with a healthcare provider for personalized advice and testing recommendations is always advisable.

Expert Opinions and Recommendations

Some doctors suggest that the test can be 99% accurate at 4 months, or that a conclusive result can be obtained at 6 weeks. However, others recommend waiting until 3 months, which is the standard protocol. Even a negative test at 4 weeks is rare to become positive at 3 months.

A doctor with whom I consulted clearly stated that a negative test at 6 weeks, while not conclusive, does provide a high level of certainty. The protocol recommends a retest at 3 months for peace of mind, as it is rare for a person to test positive at 3 months after a negative result at 4 weeks. Another recommendation is to perform a third test at 6 weeks for added assurance, using a combination screening test for both p24 antigen and HIV antibodies, which is known to be highly accurate at 45 days.

Official Statements from LabCorp and Quest Diagnostics

LabCorp and Quest Diagnostics, which conduct the duo test, declare a sensitivity rate of 97% if the test is performed 3 weeks post-exposure. The British HIV Association (BHIVA) previously had a window period of 28 days for the duo test but changed it to 45 days in the past year to ensure no infected individuals are missed. While highly accurate at 28 days, retesting at 45 days provides additional peace of mind.

Considering the above, it is clear that while a 4th generation HIV test at 28 days is highly accurate, following up with a test at 3 months is recommended for a definitive result. Additionally, performing tests at 4 weeks, 6 weeks, and 3 months can provide a comprehensive approach to HIV testing, ensuring accurate and reliable results.

Please consult a healthcare provider for personalized advice and testing recommendations.