Virtual phenotype vs genotype

The VIRA3001 study found that Virco’s forerunner to TYPE HIV-1, the Virtual Phenotype, accurately predicted responses to new regimens and appeared better able to predict the likelihood of viral load falling below 50 copies/ml than did the actual patient phenotype.1

However, the CREST study, comparing virtual phenotype results to those obtained using a genotypic assay applied to a reliable interpretive algorithm, failed to find a clear benefit to using the virtual phenotype.2

The correlation between an actual and virtual phenotype will be weaker in the case of newer drugs or unusual genotypes. To help in developing their database of available matches, Virco has been able to obtain clinical cut-offs for newer drugs from clinical trials e.g. tipranavir/r results from the RESIST study and etravirine results from the DUET study.

This information is presented in the form of conditional clinical notes, provided along with any other information that may be helpful in decision-making, such as reporting on transitional mutations. It has been suggested that looking at treatment outcomes to assess multiple mutations and mutational interactions would be just as effective, if not more so, than using virtual phenotype.



  1. Graham N et al. The virtual phenotype is an independent predictor of clinical response. Eighth Conference on Retroviruses and Opportunistic Infections, abstract 524, 2001
  2. Hales G et al. A randomised trial comparing genotypic and virtual phenotypic interpretation of HIV drug resistance: the CREST study. PLoS Clin Trials 1(3):e18. doi:10.1371/journal.pctr.0010018, 2006
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.