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HIV-1 Phenotypic Drug Susceptibility Testing

Phenotypic testing provides a direct measure of HIV-1 antiretroviral (ARV) susceptibility using a recombinant virus exposed to various concentrations of ARVs in cell culture. Results are reported as a fold change (FC) measuring response of patient virus compared to a drug-susceptible reference virus. If the FC is above an established cutoff, or threshold, the virus is determined to have reduced susceptibility to the ARV. The range of FC can provide an indication of likelihood that a patient virus will respond to that drug.

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Labcorp offers phenotypic testing for a combination of HIV-1 antiretroviral drug classes, as well as targeted testing for integrase and entry inhibitors.  

PhenoSense GT® and PhenoSense GT® Plus Integrase provide phenotypic and genotypic testing for three and four major ARV drug classes respectively.

*Nucleoside reverse transcriptase inhibitors (NRTIs); nonnucleoside reverse transcriptase inhibitors (NNRTIs); integrase inhibitors (INIs); protease inhibitors (PIs).

All phenotypic assays require a viral load of > 500 copies/mL with the exception of PhenoSense Entry® which requires a viral load of > 1000 copies/mL. 

Viral load reflex testing is available for each phenotypic assay to ensure there is adequate viral load to perform the test.