Background: Routine analysis of serum and/or plasma specimens for hepatitis C virus (HCV) RNA does not always correctly reflect the response to antiviral therapy. Analysis of whole-blood specimens for detection of viral RNA should provide more-accurate prognostic information.
Methods: Whole-blood, serum, and plasma specimens (268 sample sets) were obtained from 56 patients who did not respond to initial interferon (IFN)- alpha 2b monotherapy (5 MU every 2 days for 3 months). Specimens were analyzed for HCV RNA by 4 different types of reverse-transcriptase polymerase chain reaction (RT-PCR) (Cobas Amplicor HCV-2.0 [Roche], LightCycler real-time PCR [Roche], and 2 in-house RT-PCRs) to determine whether specimen type can predict the rate of virologic response to high-dose treatment with IFN (10 MU every 2 days) and ribavirin (1-1.2 g/day).
Results: Of the 56 patients who provided specimens, serum and plasma obtained from 18 tested negative for HCV RNA at the end of treatment, indicating a complete virologic response. In contrast, analysis of whole-blood specimens obtained at the same time revealed the presence of viral RNA in 12 of these 18 patients. All 12 subjects had relapse of HCV in serum and plasma: 11 relapsed a median of 4 weeks after the end of treatment, and 1 relapsed 20 weeks after the end of treatment. None of these 12 patients--all of whom consistently had whole-blood specimens that tested positive and plasma and serum specimens that tested negative for HCV RNA up to 20 weeks before the end of treatment--showed a sustained virologic response (P=.0002).
Conclusions: Results of whole-blood tests for detection of HCV RNA were highly predictive of viral relapse (positive predictive value, 100%) and thus may be useful tools for monitoring and tailoring IFN/ribavirin therapy. Testing of only serum or plasma specimens underestimates the true circulating HCV load and leads to an overestimation of antiviral response rates.