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faulty phenotype-geneo type results
Feb 21, 2004

After testing HIV pos. in Dec. 1996, starting therapy in Jan.1997, and continous treatment since, I recently had the phenotype and genotype testing done. The results stated that I have never taken any HIV meds. The following is a list and approximate length of time taking each: Kaletra-5 months Crixivan-6+ yrs. Epivir- 7 yrs. Sustiva- 4+ yrs. Zerit- 1 yr. AZT-7 months Videx- 2 yrs. Is this possible after a 95 adherance rate?

Response from Dr. Sherer

A negative genotype test does not mean that you have never taken any HIV meds.

It only means that there are no resistance mutations in the majority (>20%) species with which you are infected at this time while on your current regimen.

More information would be needed to interpret these results in your sitation. If, as you suggest, you have always had >95% adherence (congratulations, by the way, and keep up the good work), and you achieved good viral load suppression with all of them, then the genotype may be accurate, and you may still have wild type as your dominant species.

In that case, perhaps your regimens were changed only due to toxicity, or to simplify your regimen.

However, this genotype may have failed to detect an 'archived' mutation to one of your earlier regimens. If so, re-exposure to the same drug, or to one with cross-resistance with that drug, would then cause that resistance mutation to re-emerge.

If, for example, your regimen sequence was Crixivan plus nucs, followed by Sustiva plus nucs, and then Kaletra plus nucs, you may have an archived mutation to Sustiva which might not appear on the genotype test if you are no longer taking it.

As always, I suggest you talk about these results and what they mean with your doctor.

Trizivir resistance
Available drugs

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