[Drug resistance in antiretroviral therapy of HIV infection].
Despite impressive success of highly active antiretroviral therapy, a durable control of viral replication cannot be achieved in a substantial proportion of HIV-infected patients. The most important reason is development of resistance, defined as capability of mutant virus to replicate in the presence of a higher concentration of substance in comparison to wild-type virus. In the treated HIV-positive population resistance is prevalent in almost 50%, whereas in treatment-naïve resistance can be found in 10-14%. For diagnosis, genotypic resistance tests (sequencing of pol gene) and phenotypic resistance assays (susceptibility against antiretrovirals of an isolate in vitro) are available. A special problem is the interpretation of complex mutation patterns. Elaborate databases are implemented for this task. A number of clinical studies have demonstrated the value of resistance testing in the situation of virological failure. Resistance-guided salvage therapy was significantly more effective in these trials in comparison to former standard of care. This led to the recommendation of resistance testing in this clinical situation by German and international expert panels.