Purpose of review: Resistance testing has become an important component of the recommended care for treatment-naive and treatment-experienced HIV-infected patients in the developed world, and their use has been shown to improve clinical outcomes. Despite the widespread use of resistance testing, the clinician faces a number of challenges in optimally applying these technologies to antiretroviral management.
Recent findings: Even with the aid of a genotypic interpretation system, the interpretation of a genotype is complex and benefits from expert input. Phenotypic resistance testing is limited by cost and availability for many patients. Standard resistance testing (both genotypes and phenotypes) is unable to detect minority species. The presence of resistant minority populations has been associated with virologic failure. However, the current techniques available to detect their presence are cumbersome and not soon likely to become part of routine clinical care. The development of the chemokine (C-C motif) receptor 5 antagonists has provided new challenges in quantifying antiretroviral resistance.
Summary: Resistance testing plays a central role in the management of treatment-experienced patients. Further progress in the interpretation of resistance testing, especially as new agents are developed, will continue to add value to the care of HIV-infected patients.