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Primer on interpretation of HIV drug resistance testing

Joel E Gallant, MD, MPH
Section Editor
Martin S Hirsch, MD
Deputy Editor
Jennifer Mitty, MD, MPH


With improvements in the efficacy, safety, tolerability, and convenience of antiretroviral therapy (ART), preventing and managing antiretroviral drug resistance has become less challenging than it was in the past. Nevertheless, clinicians caring for HIV-infected patients need to understand the resistance patterns associated with specific antiretroviral medications so that they may appropriately select treatment regimens that will maximize the likelihood of viral suppression [1]. While these patterns can be complex, there are basic principles that underlie effective utilization of resistance data, which should be considered when making decisions about switching drug regimens after virologic failure.

This topic will address the major resistance patterns found in association with different medications, and how that knowledge translates into the selection of appropriate treatment regimens. The details in this topic refer mainly to resistance patterns seen with HIV subtype B, which is the most prevalent clade in the United States, Europe, Japan, Thailand and Australia. (See "Global epidemiology of HIV infection".)

Topic reviews that discuss the different types of resistance tests, as well as the selection of ART regimens for treatment-naïve or treatment-experienced patients, are found elsewhere. (See "Overview of HIV drug resistance testing assays" and "Drug resistance testing in the clinical management of HIV infection" and "Selecting antiretroviral regimens for the treatment-naïve HIV-infected patient" and "Selecting an antiretroviral regimen for treatment-experienced HIV-infected patients who are failing therapy".)


Prior to the initiation of antiretroviral therapy (ART), clinicians should obtain a careful medication history to assess the possibility of drug resistance from previous drug exposure.

Resistance testing, using genotypic and/or phenotypic assays, is also critical in guiding treatment decisions, both for treatment-naïve and treatment-experienced patients [2]. A treatment-naïve patient may have been infected with drug-resistant virus, while the treatment-experienced patient may have developed resistance as a result of non-suppressive ART. Understanding the implications of the resistance patterns for specific medications and drug classes is important for optimal patient management. (See "Overview of HIV drug resistance testing assays" and "Overview of HIV drug resistance testing assays", section on 'Genotypic resistance assays' and "Selecting antiretroviral regimens for the treatment-naïve HIV-infected patient" and "Selecting an antiretroviral regimen for treatment-experienced HIV-infected patients who are failing therapy".)


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Literature review current through: Aug 2017. | This topic last updated: Feb 07, 2017.
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