HIV treatment guidelines, including those produced by the U.S. Department of Health and Human Services (HHS) and the International AIDS Society-USA (IAS-USA), recommend drug-resistance testing for all HIV-positive people. Here's a look at when these tests should be used:
When HIV is first diagnosed. Knowing if you've been infected with a drug-resistant strain of HIV—and which drugs your virus is resistant to—can be very helpful. For the most accurate results, you should be tested for HIV drug resistance soon after you are diagnosed as HIV positive, even if you won't be starting treatment for several months or years (the information will be recorded in your medical file and help guide treatment when the time comes).
It is important to note, however, that drug-resistance testing does not always produce accurate results when used in this manner. Soon after a drug-resistant strain enters the body, it begins reproducing. Over time, a wild-type strain of HIV can emerge, forcing the drug-resistant strain(s) to go into hiding and escape detection using drug-resistance testing. In other words, testing may not produce reliable information if too much time has passed since infection occurred.
If treatment doesn't appear to be working. If viral load fails to become undetectable after a new treatment regimen is started, or becomes detectable again after a period of being undetectable, drug-resistance testing may help determine the cause. For best results, the test should be conducted while you are on your regimen—provided that your viral load is detectable—or within four weeks of discontinuing treatment.
If no drug resistance is found, the problem might be poor adherence, absorption difficulties or drug–drug interactions. It is best to remedy these problems before resistance mutations develop. If drug resistance is found, these tests can help determine which medications have stopped working for you (people rarely develop resistance to all three or four drugs being taken) and also help figure out which medications to switch to.
During pregnancy. If you are HIV positive and become pregnant, the most effective way to reduce the risk of transmitting the virus to your baby is to get your viral load undetectable and keep it there—at least until your baby is born. Drug-resistance testing before and during treatment can help achieve this important goal.
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