I wanted to share a bit of this article written by Tracy Swan of Treatment Action Group (TAG). Tracy is an expert in HIV and HCV. She understands virology better than anyone I know. I know there have been other posts on this subject, but this one has some new theories. I thought it was interesting.
Viral-load test results at week four and at end of treatment (EOT)—a mainstay of HCV treatment monitoring—do not always predict the outcome of HCV treatment. Nearly everyone becomes undetectable within weeks of starting DAAs, but some people relapse within weeks of finishing treatment. In effect, early responses do not predict treatment success, nor do they predict treatment failure with DAA regimens.
Most people with detectable virus at week four will be cured, according to Sreetha Sidarthan from the Institute of Human Virology in Baltimore and colleagues, who analyzed results from the ERADICATE and SYNERGY trials of sofosbuvir-based regimens. Of the 17 people with detectable RNA at week 4 in SYNERGY, 100 percent were cured. In ERADICATE, 32 of 50 people had detectable HCV RNA at week 4; ultimately, 31 of the 32 were cured. EOT testing did not reliably predict cure either.
Researchers have speculated about why HCV may be detectable at the end of treatment in people who are actually cured. One such theory developed by Thi Huyen Tram Nguyen of the French Institute of Health and Medical Research and colleagues suggests that some defective virus lingers after HCV treatment has stopped production of new virus. This virus cannot infect liver cells or reproduce, but persists after treatment is finished, only to die off a few weeks later.