Expert Advice Matters When Interpreting Resistance Testing
Reported by Jules Levin

Results from the HAVANNA Trial (abstract 434) were reported at the Retrovirus Conference. These results were reported by C. Tural from Barcelona, Spain and highlight one of the key impediments to maximizing the use of resistance testing. Interpreting the results reported from resistance testing takes expertise, and if doctors do not have such expertise they may not be able to interpret testing as well. If they can't interpret the results very well this hampers their ability to select the best regimen based on the testing results. Tural and a Spanish research group reported data from the Havana Trial of genotypic resistance testing.

The data from this study suggest "expert advice" in interpreting results from resistance testing may be crucial to making treatment decisions. The data also suggests that some doctors have more expertise in making treatment decisions than others. 274 ART -experienced patients were randomized to change therapy based on genotypic testing or no genotypic testing (using the Trugene genotyping kit - VGI), and to receive expert advice from a committee of virologists and clinicians or no expert advice. All genotyping was done using the Trugene genotyping kit from Visible Genetics (VGI) with results interpreted by a software program (Retrogram v1.0, Virology Networks). At baseline, mean cd4 and viral load were 388 and 4 log (about 10,000 copies/ml). A week 24, there was a significant difference in percent <400 copies/ml between the groups receiving genotyping and not receiving genotyping (57% vs 42%), the expert advice and no expert advice groups (59% vs 41%).

Interestingly, the greatest difference was between the group receiving expert advice with genotyping and the group without expert advice and without genotyping (69% vs 36%). The study authors concluded there was a suggestion that expert advice may add to the benefit of genotyping in heavily pretreated patients. In the analysis of the genotyping arm, the 3rd failure group had a significant viral load reduction (1.1 log vs 0.7 log), but the 1st and 2nd failure groups did not. The viral load differences between the groups receiving geno or not (-1.1 log vs 0.8 log) and expert advice or not (-1 log vs 0.9 log) were statistically significant.