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4th Gen hiv combo

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  • 4th Gen hiv combo

    I m a senior physician and noticed that your center claims rapid hiv combo test conclusive at 28 days. I have not found a single medical guideline which agrees with your recommendation. Most guidelines claim that rapid combo test is less sensitive to lab based 4th generation test. There is even discrepancy with regards to conclusive results in guidelines which vary 4 weeks, 6 weeks and 12 weeks.
    CDC says 45 days.
    I m not sure which guidelines are you relying upon?
    Have y encountered cases who turned positive after 4 weeks?

  • #2
    Hi, thank you for your input.
    Yes, you are correct to say there are several differing guidelines for HIV testing worldwide. However, we have multiple studies on diagnostic HIV tests that demonstrate the reliability of 4th generation testing at 2-4 weeks - one such summary of some of these studies can be found here:
    Which essentially shows that 4th generation testing has a sensitivity of > 99.8% already at 2 weeks post-exposure.

    As clinicians, we must also take into account the individual exposure risk, and the subsequent negative and positive predictive value of the the test results. Guidelines are continually being updated as testing methods improve, and of course national level guidelines can take some time to evolve and will always tend to be more conservative than necessary in their estimates. All guidelines will also recommend that the physician make the decision for testing together with the patient based on their individual circumstances and risk assessment.

    We have not encountered anyone who has tested negative at 4 weeks post-exposure with 4th generation testing that tested positive thereafter.