Measuring Resistance

Managing Resistance to HIV Therapy

Next

Measuring resistance
Resistance to antiretroviral drugs can be assessed phenotypically or genotypically.

Phenotypic assessment
Drug resistance is measured in cell cultures containing the virus. Resistance is defined as a fourfold or greater increase in the concentration of drug needed to suppress viral replication. This method is expensive and slow (takes weeks).

Genotypic assessment
Resistance mutations are identified directly in the virus, using gene probes and other genetic code sequencing methods. Probes assessing mutations in reverse transciptase are increasingly available, with probes for protease inhibitors mutations currently under development.

However, these tools will need to be used in conjunction with other disease markers, such as viral load, C04 cell count and clinical status, and with appreciation of their limitations.

Resistance Quiz