Thirty-two trials met the inclusion criteria. Twenty trials contained a placebo or untreated control group and twelve examined difference dose and duration of interferon therapy. The number of patients in each trial ranged from 18 to 323 with 552 randomised participants in total.
In biochemical responses, interferon alfa-2b showed a statistically significant improvement among treated patients (20 studies), OR = 25.1 (95% CI: 15.0, 42.2; p < 0.0001). Sustained response for at least 6 months after discontinuation of therapy (18 trials) had an OR of 17.8 (95% CI: 8.5, 37.3; p < 0.0001) in favour of treated patients.
In virological responses, interferon alfa-2b showed a statistically significant improvement among treated patients (5 studies), OR = 9.4 (95% CI: 3.4, 25.7; p < 0.001). Absence of circulating HCV RNA was maintained for 6 months after discontinuation of therapy in 8% of treated patients and 1% of untreated patients with an OR of 8.6 (95% CI: 1.0, 74.8; p < 0.0001) in favour of treated patients but this was not statistically significant.
In histological responses, interferon alfa-2b showed a statistically significant improvement among treated patients (4 studies), OR = 4.8 (95% CI: 2.3, 10.1; p < 0.0001). Only one study met the now-standard histological end-point of greater than or equal to 2-point improvement in the histology activity index. The response rate for this trial was 40% in treated patients and 12% in controls.
In the comparison of varied duration of therapy (6 studies) a difference in end-of-treatment biochemical response was observed in only one trial. At the end-of-treatment, 45% of those who received 6 months of therapy had normal ALT values compared with 47% of those who received 12 to 24 months of interferon therapy. The composite OR was 1.09 (95% CI: 0.80, 1.49; p = 0.59) which was not statistically significant. There was an increase in 6-month sustained response after discontinuation of therapy in patients who received treatment for 12 to 24 months compared with 6 months of 27% versus 14% respectively, the OR was 2.95 (95% CI: 1.9, 4.5; p < 0.001).
In the comparison of different doses (4 trials), the patients who received higher doses of interferon had a higher biochemical response of 61% compared to 52% in those receiving 3 MU with an OR = 1.8 (95% CI: 1.1, 3.0; p < 0.02). The 6-month sustained responses were 28% and 19%, OR = 2.2 (95% CI: 1.2, 4.0; p< 0.01).