Resistance testing for the treatment of chronic hepatitis C with direct acting antivirals: when and for how long?

The need to test for resistance associated substitutions (RAS) has been intensively debated in the past two years. In the absence of pangenotypic combinations, it seems reasonable that, if available, RAS testing in the NS5A gene at baseline for genotypes 1a and 3 may help to avoid overtreatment in terms of ribavirin usage and/or prolonged treatment duration. When patients fail treatment, RAS testing may also be useful to guide the selection of the new regimen, especially for those that need urgent retreatment and that have failed a combination including an NS5A inhibitor. However, there are new drugs in the pipeline that in combination are pangenotypic, very potent and with a high genetic barrier to resistance. In this new scenario, RAS testing may not play such an important role.