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Education > Clinical Updates

Clinical Update 10 - News from the 16 ^th European HIV Drug Resistance Workshop

Budapest, Hungary
March 26-28, 2008

The interpretation of quantitative phenotypic resistance information via clinical cut-off values on the virco®TYPE HIV-1 report can assist HIV providers in optimizing combination antiretroviral therapy. Virco has previously described a uniform and consistent 4-step methodology to define clinical cut-off values for all drugs listed on the report. Lee Bacheler and colleagues from Virco presented new information at the 6th European HIV Drug Resistance Workshop that described two recent updates to the virco®TYPE HIV-1 methodology. These updates include a new approach to calculating fold-change values for HIV viral sequences with mixtures and a substantially expanded clinical outcome dataset for the calculation of clinical cut-offs. The impact of these changes were evaluated on more than 50,000 routine clinical samples submitted for analysis by Virco between 2005 and 2007

For viruses with mixtures, fold-change values are now calculated by taking into account the contribution of the mutation with the highest level of expected resistance. This new approach provides a conservative interpretation of drug resistance.

The clinical outcome dataset used to calculate CCOs expanded from 2935 treatment change episodes (TCE) in 2006 (2596 used to develop CCOs, 339 reserved for validation) to 8849 TCEs available by mid 2007 (6550 for development, 2299 reserved for validation). The updated outcome database includes more data on patients with higher levels of baseline resistance to components of their treatment regimen. The clinical cut-off values calculated on this expanded dataset were largely consistent with earlier values (remaining within the 90% confidence intervals).

The impact of both of these changes on the resistance analyses reported by Virco was evaluated on more than 50,000 isolates submitted to Virco for routine resistance testing in 2005-2007. After applying both of these recent updates to the samples analyzed, the changes observed in the resistance analysis were moderate.

Data from this new approach provide a conservative assessment of potential resistance based on mutations detected in the viral genotype and eliminates a potential shortcoming of phenotyping by considering the full resistance weight of mutations that may result in sub-optimal responses when present in mixtures.

If you are interested in viewing the complete poster, please click here.

If you would like to download a slide kit which summarizes this data, please click here.

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