Resistance testing: phenotype
DEFINITION
- Phenotypic resistance assays use a patient’s HIV RNA plasma-derived gene sequences (RT, PR, integrase and envelope) to measure HIV replication at different concentrations of antiretroviral drugs.[3]
- Interpretation of phenotype is based on two important clinical cutoffs: (1) lower cutoff or the value above which clinical response is diminished (partial susceptibility); and (2) upper cutoff or value above which no clinical response is expected.[2]
- Phenotypic testing compares the activity of a patient’s HIV to a control strain with known susceptibility to a specific drug.
- Phenotypic co-receptor tropism assays detect CCR5, CXCR4, or dual/mixed (D/M)-tropic virus. Viral tropism is the ability of HIV to bind to different co-receptors on target cells to achieve viral entry. Phenotypic co-receptor tropism assay is used to assess activity of CCR5 antagonist (maraviroc).
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Last updated: February 12, 2022
Citation
Spacek, Lisa A. "Resistance Testing: Phenotype." Johns Hopkins HIV Guide, 2022. Johns Hopkins Guides, www.hopkinsguides.com/hopkins/view/Johns_Hopkins_HIV_Guide/545178/all/Resistance_testing:_phenotype.
Spacek LA. Resistance testing: phenotype. Johns Hopkins HIV Guide. 2022. https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_HIV_Guide/545178/all/Resistance_testing:_phenotype. Accessed June 1, 2023.
Spacek, L. A. (2022). Resistance testing: phenotype. In Johns Hopkins HIV Guide https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_HIV_Guide/545178/all/Resistance_testing:_phenotype
Spacek LA. Resistance Testing: Phenotype [Internet]. In: Johns Hopkins HIV Guide. ; 2022. [cited 2023 June 01]. Available from: https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_HIV_Guide/545178/all/Resistance_testing:_phenotype.
* Article titles in AMA citation format should be in sentence-case
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