Prevalence of Genotypic and Phenotypic Resistance to Antiretroviral Drugs in a Cohort of Therapy-Naïve HIV-1 Infected U.S. Military Personnel [Wegner SA, et al. AIDS 2000; 14: 1009]: The authors investigated genotypic and phenotypic resistance in a cohort of 114 treatment-naïve military recruits with HIV infection. The genotypic method used VircoGEN, which integrates mutational patterns to define strains as sensitive, intermediate resistant or resistant. With phenotypic resistance, a 5-10 fold increase in IC50 compared to wild-type virus defined intermediate resistance and >10-fold defined resistance. Using these definitions, the overall rate of intermediate or high-level resistance was 22% by genotypic assay and 30% by phenotypic assay. The breakdown by level of resistance and by drug class is summarized as follows:
| HIV resistance to antiretroviral agents in 114 treatment-naïve patients |
| |
Intermediate Resistance |
Resistant |
| Genotype |
Phenotype |
Genotype |
Phenotype |
| NRTI |
3.2% |
6.6% |
1.1% |
1.1% |
| NNRTI |
9.5% |
18.7% |
6.3% |
7.7% |
| PI |
8.4% |
0 |
1.1% |
1.1% |
Comment: This is an exceptional study in that it represents a diverse sampling of the U.S. population and shows that primary resistance could pose a substantial problem. At the present time, resistance testing is not advocated in the IAS-USA guidelines or the DHHS guidelines in chronically infected, treatment-naïve patients. The rationale is based in part on the assumption that resistant strains will often be sequestered and therefore not measured. Nevertheless, the results of this and some other studies suggest that we are reaching the point at which such testing may be advocated because, although it will not define which drugs will work, it will presumably indicate the drugs that won't work.
posted 7/19/2000
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