If real time resistance testing is not routinely included in studies, then people may simply choose to get it independently. Researchers, however, fear that people who get their own results in real time may be more likely to drop out of studies when their regimens fail or show signs of resistance. Defining Drug Resistance One area of contention between drug developers and resistance test developers is the level of drug resistance that should be considered significant. It is usually not possible to increase the dose of a drug much beyond this because this will also increase the number and severity of side effects. The ADAC recommended that the amount of resistance to a drug that renders it ineffective should be determined for each individual drug, rather than having a single standard apply to all drugs.
Several studies show that resistance testing can determine which drugs in a regimen no longer work.
But few studies show that resistance testing can predict the success of a new regimen. New preliminary results presented at the ADAC meeting show that resistance testing can predict short-term response to a new drug. The phenotypic test was used on 274 people with a viral load of at least 2,000 copies HIV RNA who were taking at least two nucleoside analogue drugs and one protease inhibitor. The other half had delayed phenotypic testing results and could change therapies based only on the other available information. After 16 weeks, the group with immediate testing had much better anti-HIV therapy responses.