AIM: To investigate the efficacy of virological response(VR) to telaprevir(TVR)-based triple therapy in predicting treatment outcome of hepatitis C.METHODS: This prospective, multicenter study consisted of 253 Japanese patients infected with hepatitis C virus(HCV) genotype 1b. All received 12 wk of TVR in combination with 24 wk of pegylatedinterferon-α(IFN-α) and ribavirin. Serum HCV RNA was tested at weeks 1, 2, 3, 4, 6, 8, 12, 16, 20, and 24. VR was defined as undetectable serum HCV RNA. Sustained virological response(SVR) was VR at 24 wk after the end of treatment and was regarded as a successful outcome.RESULTS: Of 253 patients, 207(81.8%) achieved SVR. The positive predictive value of VR for SVR was 100% at week 2, after which it gradually decreased, and was over 85% to week 12. The negative predictive value(NPV) gradually increased, reaching 100% at week 12. The upslope of the NPV showed a large increase from week 4(40.6%) to week 6(82.4%). There was a moderate concordance between the SVR and VR at week 6(kappa coefficient = 0.44), although other VRs had poor concordance to SVR. Multiple logistic regression analysis extracted VR at week 6(P < 0.0001, OR = 63.8) as an independent factor contributing to SVR. In addition, the interleukin-28 B single nucleotide polymorphism and response to previous pegylated-IFN-α and ribavirin therapy were identified as independent factors for SVR.CONCLUSION: VR at week 6, but not at week 4, is an efficient predictor of both SVR and non-SVR to TVRbased triple therapy. AIM: To investigate the efficacy of virological response (VR) to telaprevir (TVR) -based triple therapy in predicting treatment outcome of hepatitis C. METHODS: This prospective, multicenter study consisted of 253 Japanese patients infected with hepatitis C virus (HCV) genotype 1b. All received 12 wk of TVR in combination with 24 wk of pegylated interferon-α (IFN-α) and ribavirin. Serum HCV RNA was tested at weeks 1, 2, 3, 4, and 24. VR was defined as undetectable serum HCV RNA. Sustained virological response (SVR) was VR at 24 wk after the end of treatment and was considered as a successful outcome .RESULTS: Of 253 patients, 207 (81.8%) achieved SVR. The positive predictive value of VR for SVR was 100% at week 2, after which it gradually decreased, and was over 85% to week 12. The negative predictive value (NPV) gradually increased, reaching 100% at week 12. The upslope of the NPV showed a large increase from week 4 (40.6%) to week 6 (82.4%). There was a moderate concordance betw Multiple logistic regression analysis extracted VR at week 6 (P <0.0001, OR = 63.8) as an independent factor contributing to SVR. In addition, the interleukin-28 B single nucleotide polymorphism and response to previous pegylated-IFN-α and ribavirin therapy were identified as independent factors for SVR.CONCLUSION: VR at week 6, but not at week 4, is an efficient predictor of both SVR and non-SVR to TVRbased triple therapy.