People with hepatitis C virus (HCV) whose physicians at the Department of Veterans Affairs (VA) ordered drug  resistance tests show that more than half have a virus with resistance mutations. Researchers at the VA analyzed data on resistance mutations related to the NS3, NS5A and NS5B genes as found in samples from 224 people that were taken from 26 VA medical centers between February and August 2015.

Results were presented at the Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) in San Francisco.

The samples were only tested for resistance to the specific genes as per the orders of the individuals’ physicians, so all three genes were not tested in all the samples. A total of 220 (98 percent) samples yielded reportable results.

A total of 150 genotype 1a samples were tested, as were 40 samples of genotype 1b, 20 of genotype 3a, 6 of genotype 2b, 3 of genotype 4a and 1 of genotype 2a.

The treatment history was known for 176 (80 percent) of the samples. Out of that group, 25 were samples from those who had only been treated with interferon and ribavirin.

Among the 52 samples from treatment-naive people, 31 (60 percent) had one or more drug resistance mutations. Among the 99 samples taken from people previously treated with direct-acting antivirals, 57 (58 percent) had one or more drug resistance mutations.