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Resistance Testing
Drug resistance testing plays an important role in all stages of the HIV treatment continuum. In order to optimize the use of resistance testing, it is important to choose the right test at each stage of treatment. Below is a graph depicting the value of each resistance assay methodology in relationship with treatment experience. Further down, you will find a written explanation of the technology relative to the stage of therapy.
(click on thumbnail for enlarged version)
Genotype Resistance Testing (GeneSeq™ HIV)
Acute infection and early lines of therapy — genotypic testing can provide relatively straightforward information for early-stage treatment planning; test results become more difficult to interpret as treatment experience increases. Low incidence of disagreement between genotypic and phenotypic results at this stage.
Phenotype Resistance Testing (PhenoSense™ HIV)
Treatment failure in middle lines of therapy as the number of mutations increases — phenotypic testing provides individualized, quantitative results through a direct measure of drug susceptibility; quantitative nature provides greater insight into degrees of susceptibility rather than the binary results of genotyping that can be overly complex. Disagreement between genotypic and phenotypic results is typically increasing.
Combined Phenotype + Genotype Resistance Testing
(PhenoSense GT™)
Later stages of therapy with multi-drug resistant virus — the degree of susceptibility (phenotype) plus the build-up of mutations (genotype) are highly valuable pieces of information for optimizing therapy after multiple treatment failures; genotype identifies mixtures of wild-type and resistant viruses. High level of disagreement between genotypic and phenotypic results at this stage.
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