AIM: To evaluate the aspartate aminotransferase (AST) to platelet ratio index (APRI) as a predictive factor of early viral response in chronic hepatitis C naive patients.METHODS: We performed an ambispective casecontrol study. We enrolled chronic hepatitis C naive patients who were evaluated to start therapy with PEGylated interferon a-2b (1.5 mg/kg per week) and ribavirin (> 75 kg: 1200 mg and < 75 kg: 1000 mg). Patients were allocated into two groups, group 1: Hepatitis C patients with early viral response (EVR), group 2: Patients without EVR. Odds ratio (OR) and 95% confidence interval (CI) were calculated to assess the relationship between each risk factor and the EVR in both groups.RESULTS: During the study, 80 patients were analyzed, 45 retrospectively and 35 prospectively. The mean ± SD age of our subjects was 42.9 ± 12 years; weight 70 kg (± 11.19), AST 64.6 IU/mL (± 48.74), alanine aminotransferase (ALT) 76.3 IU/mL (± 63.08) and platelets 209 000 mill/mm3 (± 84 429). Fifty-five (68.8%) were genotype 1 and 25 (31.3%) were genotype 2 or 3; the mean hepatitis C virus RNA viral load was 2 269 061 IU/mL (± 7 220 266). In the univariate analysis, APRI was not associated with EVR [OR 0.61 (95% CI 0.229-1.655, P = 0.33)], and the absence of EVR was only associated with genotype 1 [OR 0.28 (95% CI 0.08-0.94, P = 0.034)]. After adjustment in a logistic regression model, genotype 1 remains significant.CONCLUSION: APRI was not a predictor of EVR in chronic hepatitis C; Genotype 1 was the only predictive factor associated with the absence of EVR in our patients.