First, we have to point out a mistake that Dai et al. made in their letter: the rapid virological response (RVR) and sustained virological response (SVR) rates are described inversely with respect to our data and maybe with respect to their data.

Dai et al. reported that the SVR rate of 64% in their study is apparently higher than the rate of 45% in our study. We think that this difference can be attributed to the difference in the mean ages of the patients enrolled in the two studies. The mean age in their study seems to have been around 50 years1 and was over 10 years lower than that in our study (62 years old). Younger patients tended to show higher SVR rates in our study as well, and the SVR rate in patients who were younger than 55 years old was 61%, which is comparable to the rate reported by Dai et al.

It is possible that a higher administration dose of ribavirin during the first 4 weeks is associated with a higher RVR rate. However, we cannot comment on this because our study was not designed for that purpose.

We adopted the definition of high viral load generally used in Japan (105 IU/mL). Since Dai et al. suggested that a difference in the definition of high viral load influenced the results, we recalculated factors associated with SVR in 103 patients whose viral load was higher than 4 × 105 IU/mL and also in 89 patients whose viral load was higher than 8 × 105 IU/mL. The same four prediction factors as those provided by the original analysis of 120 patients whose viral load was higher than 105 IU/mL were again selected.

Our algorithm cannot be directly applied to other populations directly because clinical backgrounds differ among countries. However, we think that our study is applicable on a global scale because it has clearly shown that a combination of viral and host factors is effective for predicting the response to peg-interferon alpha and ribavirin combination therapy.


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Akihiro Matsumoto M.D., Ph.D.*, Eiji Tanaka M.D., Ph.D.*, * Department of Medicine Shinshu University School of Medicine Matsumoto, Japan.