Maybe. Based on what is known about HIV's error-prone reproduction process (see "How Do Mutations Occur Before Antiretroviral Therapy is Started?"), it is safe to assume that all HIV-infected people have at least a few forms of HIV that are resistant to individual drugs before therapy is started. However, these strains are often too limited in number and strength to compete with wild-type virus, and they stand a good chance of being killed off by starting combination antiretroviral therapy. In other words, genotypic or phenotypic testing might not provide an accurate picture of drug resistance before therapy is started.
Drug-resistance tests might prove to be useful for people infected with multiple-drug-resistant (MDR) strains of HIV. Soon after an MDR strain enters the body, it begins reproducing. Over time, a wild-type strain of HIV emerges and dominates the viral population. Thus, in order for drug-resistance tests to be used, blood will probably need to be drawn soon after infection takes place (i.e., within a few weeks after infection occurs). Unfortunately, only a small percentage of people know when they are infected or immediately go to see a healthcare provider.
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