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How accurate is the 4th generation HIV combo test on 24 days while on pep medication?

Question: 

I have unprotected vaginal intercourse with a sex worker. I am very regret on what i did and after 62 hours i am on the PEP medication. Throughout the PEP medication, i am having the side effects like nausea & dizziness almost everyday until now (24th post exposure). I have taken a 4th generation HIV combo rapid test with Alere HIV combo. The result came out negative. Would the result be accurate enough? I am having serious anxiety and go to different doctors everyday. Please help

Answer: 

Hi there,

Thank you for your inquiry. From what we gather from the question, you are inquiring about the accuracy of the negative result you received following 4th Generation HIV "Combo" or "DUO" testing. We assume you are asking whether your results have been influenced specifically by the PEP medication you have been taking for approximately 24 days post exposure.

Based on this scenario, and the risk of your exposure (unprotected vaginal intercourse is considered by official HIV transmission guidelines to be an act of High Risk: Evidence of transmission through these activities and is the majority of cases of transmission), you were responsible in seeking immediate and adequate treatment for the degree of your exposure.

Biomedical treatment options for HIV prevention such as PEP and PrEP are generally known to cause little side effects, yet have been associated with symptoms such as tiredness, nausea, vomiting, and diarrhoea (4).

It appears as though you are experiencing some of these side effects. If your side effects continue or worsen please seek help from an HIV specialist who can manage or monitor your symptoms going forward.

The 4th Generation Combo tests have the sensitivity and specificity of 100% for patients with chronic HIV infection (1), and, when routine post-PEP HIV testing guidelines are followed adequately, have an accuracy of 99.9% (2).

Although you had received a negative result from your 4th Generation test, it is essential that these official post-PEP HIV testing guidelines are followed for completely competent and accurate results. Post-PEP testing guidelines are as follows:

"Individuals receiving PEP should have HIV testing at baseline, 3 weeks, 6 weeks, and 3 months after completing PEP" (3).

Due to this, we recommend you follow post-PEP testing guidelines by seeking follow up testing approximately 3 weeks, 6 weeks and 3 months after completing PEP for completely accurate results.

All the best,

AIDS Vancouver Helpline/Online, Cody