Source Hôpital Beaujon, Clichy, France.

BACKGROUND: It is unclear whether the magnitude of reduction in hepatitis C virus (HCV) RNA between baseline and week 4 of treatment influences the probability of achieving a sustained virological response (SVR) in patients without a week 4 rapid virological response (RVR).

METHODS: Data were retrospectively analysed from two studies in which treatment-naive patients received peginterferon alfa-2a (40KD) 180μg/week plus ribavirin 1000/1200mg/day for 48 weeks. 558 genotype 1 patients with evaluable HCV RNA at baseline and week 4 were grouped according to RVR status: RVR (HCV RNA <50IU/mL) or no RVR. Non-RVR patients were subdivided into discrete mutually exclusive categories according to week 4 HCV RNA; per category, the proportion of patients with undetectable HCV RNA at week 12 was calculated and of these, the proportion with an SVR.

RESULTS: Overall, 88% of RVR patients and 43% non-RVR patients achieved an SVR (p<0.0001). Among non-RVR patients, SVR rates were 77%, 61%, 43%, 27% and 13%, respectively (trend test p<0.0001) in those with unquantifiable HCV RNA or ⩾3log(10), ⩾2log(10), ⩾1log(10), or <1log(10) drop to week 4. In patients HCV RNA positive at week 4, SVR rates were 67% for those negative at week 12 versus 17% (HCV RNA positive patients or who had missing values at week 12 [p<0.0001]).

CONCLUSIONS: The probability of achieving SVR is graded in relation to the magnitude of reduction in HCV RNA at week 4 and 12. Patients with a ⩾3log(10) drop in HCV RNA at week 4 have a high probability of achieving an SVR.