However, the specific genotypes were not listed for each group. Also, there were no significant differences on liver biopsies when comparing the two groups. The mean liver inflammation score was 2.2 in methadone users and 2.1 in non-users. There are several potential confounding factors that account for some the differences. First, the absence of an IDU history in those 101 patients does not mean that such a history did not exist.
Patients often are reluctant to admit such behavior.
Second, there was no breakdown of race-ethnicity in either group. Third, the authors did not indicate whether any of those who were not taking methadone at that time had taken it in the past. Other information was omitted that has not been associated with a differential in HCV viral loads in past studies, but might still represent potential confounding factors. First, ongoing IDU behavior in the non-methadone users might be much more frequent than among the methadone users. Third, it would have been helpful if the authors had made an estimate of the duration of HCV infection in both groups.