two lab techs observing a vail. observing the specimen

HIV-1 Combination Phenotype and Genotype Resistance Assays

The combination of phenotype and genotype provides a more complete picture of HIV-1 resistance.  

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A more complete picture

Genotypic testing detects mutations associated with antiretroviral resistance and utilizes interpretive algorithms to predict susceptibility of antiretrovirals (ARVs).  Phenotypic testing provides a direct measure of drug susceptibility by quantifying the ability of ARVs to inhibit HIV reproduction in cell culture.  The quantitative measure of drug susceptibility is compared with a wild-type, ARV-susceptible reference strain of HIV and translated to a Fold Change (FC) value.1

The combination of these two assays overcomes the limitations associated with genotypic or phenotypic testing alone.  In cases of discordance between the two technologies, a net assessment, based on a proprietary, rules-based system, resolves the difference.

The addition of phenotypic to genotypic testing is noted in US Department of Health and Human Services (DHHS) guidelines as preferred for patients who may benefit from drug resistance testing due to known or suspected complex drug resistance patterns.2 
 

Labcorp offers two assays of 
combined phenotype and genotype.

ORDER CODE 551690

PhenoSense GT® 

Evaluates ARV susceptibility for ARV drug classes:

  • Nucleoside reverse transcriptase inhibitors (NRTIs)
  • Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
  • Protease inhibitors (PIs)
View Test Specifications

Order Code 551920

PhenoSense GT® Plus Integrase

Evaluates ARV susceptibility for ARV drug classes:

  • Nucleoside reverse transcriptase inhibitors (NRTIs)
  • Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
  • Protease inhibitors (PIs)
  • Integrase inhibitors (INIs)
View Test Specifications

References:

  1. Parkin N, et al. Phenotypic and genotypic HIV-1 drug resistance assays provide complementary information. J. Acquir. Immune Defic. Syndr. 2002; 31(2):128-136.
  2. Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the Use of Antiretroviral Agents in Adults and Adolescents with HIV. Department of Health and Human Services. Available at https://clinicalinfo.hiv.gov/sites/default/files/guidelines/archive/AdultandAdolescentGL_2021_08_16.pdf. Accessed June 26, 2023