HCV genotype 1 subtypes (1a and 1b): similarities and differences in clinical features and therapeutic outcome.

Background and aim: The majority of clinical trials assessed treatment response rate among HCV-1a and 1b patients as a single group. Moreover only few trials were sufficiently powered to detect an eventual difference, whereas the observed data were conflicting with some studies reporting a lower efficacy of PEG-IFN and RIBA in HCV-subtype 1a, and some others unraveling an opposite finding. Material and methods: We aimed to evaluate the baseline similarities and differences between the two HCV-1 subtypes, 1a and 1b, on pre-treatment and on-treatment predictors of response to standard therapy. Results: Six factors differentiate genotype 1a vs genotype 1b: the more frequent male sex (74% vs 56%; p<0.001); the age younger than 50 years (63% vs 30%; p<0.001); the value of BMI (24 vs 25; p<0.042); higher value of platelet count (209x103 vs 186x103; p<0.001); less frequent severe liver fibrosis (70% vs 52%; p<0.001) and finally less frequent type 2 diabetes comorbidity (5% vs 12%; p<0.005). All other parameters resulte equally dis-tributed between the two HCV 1 subtypes. Of note, the IL28B polymorphisms and the RVR resulte equally distributed between the two HCV 1 subtype. SVR is achieved by 38% of genotype 1b and by 45% of genotype 1a even in this difference of 7% is not statistically significant (p=0.076). Three factors were independently associated in subtype 1a: female gender, IL28B polymorphism, and RVR; and three factors independently associated in subtype 1b: low baseline serum HCV-RNA concentration (<400.000 IU/mL); IL28B polymorphism, and RVR. Conclusions: The study shows that genotype 1a is more frequently observed in young male patients. It also identifies some differential predictive features of SVR between the two subtypes, a finding which would imply that the two subtypes must be separately evaluated in future therapeutic trials.