Genotypic resistance tests for the management of postexposure prophylaxis.

Single witness: Given the increased utilization of highly active antiretroviral therapy (HAART) and the growing number of patients harbouring a drug-resistant virus, the potential exists to become infected with drug-resistant HIV. Available data suggest the emergence of drug-resistant HIV among source persons for occupational exposures. Despite this non-negligible rate, none of the health-care workers have become infected with HIV. The prevalence of antiretroviral resistance is high among source patients who reported any use of antiretroviral agents and is rare among those who reported no history of use, and in the majority of cases of failure of postexposure prophylaxis (PEP), the source was reported to have experience of the same agents included in the PEP regimen provided to the exposed individual. There are no data available to demonstrate that resistance testing leads to improvements in PEP outcomes. In fact, testing HIV isolates from a source patient, when available, for antiretroviral resistance would be of no immediate significance, as PEP should be initiated within hours of the exposure. The source patient's treatment history may be helpful in predicting which resistance mutations might be present in the source isolate.