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URGENT! Resistance test
Feb 24, 2004

I started back on Combivir/Sustiva on May 13 after an 18-month holiday. On August 19 my VL was 807. On November 18 it went up to 1260. A repeat VL and genotype was drawn on December 8. VL was 1260, exactly the same as before. Stopped Sustiva on Dec 23 and switched to Kaletra for 7 days before stopping everything Dec 29.

I finally got my resistance test results on January 8. It showed no evidence of resistance to NRTIs, NNRTIs and PIs.

My questions: Do you think the resistance test is accurate? If so, why couldn't I get my VL down to undetectable? I'm 99.9 adherent and these drugs worked before. And most urgent: Should we repeat the resistance test? I understand the window for getting a meaningful result is closing.

Response from Dr. Sherer

I can't answer your question with the information provided, because I don't know all of your treatment history, i.e. the regimen(s) you took before the holiday, nor do I know the circumstances when you stopped your drug 18 mos ago, though you said that EFV 'worked in the past'.

Genotype tests are accurate but limited in what they can tell you. They will not detect minority species (<20%). Since you have previously been on treatment, you may have mutations that are 'archived' and no longer show up. However, this genotype result suggests no resistance to your current regimen, i.e. Sustiva and Combivir, so you and your physician could reasonably decide to resume the same regimen and observe.

So why were you unable to get below detection? One variable that impacts the time it takes to become undetectable is the baseline viral load, which if over 100,000 may take > 6 months to fall below detection.

Another option for you and your physician to consider would be to 'intensify' the regimen with an additional drug, e.g. use trizivir twice daily instead of combivir, though this strategy remains of unproven benefit. I would not repeat the genotype test at this point, but rather resume therapy and monitor carefully with your doctor.

Will all treatments eventually fail / vaccine hopes
understanding resistance testing

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