Prognostic Value of Resistance Testing

Retrospective analyses of many studies have established the value of resistance testing as a predictor of treatment response in patients changing therapy. In these studies, resistance testing was performed on stored samples from patients experiencing virologic failure that had been obtained at the time a new regimen was initiated.

Results of the resistance assays were used to classify patient viruses as sensitive or resistant to the drugs in the new regimen. In a meta-analysis that combined results of several retrospective studies, resistance to the drugs in the new regimen predicted a significantly greater likelihood of treatment failure (17).

Conversely, the more drugs in the new regimen to which the virus was sensitive (as predicted by the resistance assays), the lower the chance of treatment failure. Several of these studies showed that drug resistance remained a significant independent predictor of the likelihood of treatment failure even after controlling for treatment history. In other words, resistance testing provided provided significant additional prognostic information over and above the information available from treatment history alone.

4/15/01

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