GPT and substance abuse: Compared to the risk-based phase, patients newly diagnosed with HCV Ab + after the birth-cohort intervention were significantly less likely to have a history of any substance abuse (30.5 % vs. 49.5 %, p = 0.02), elevated alanine transaminase levels of > 40 U/L (22.0 % vs. 46.7 %, p = 0.002), or the composite any risk-associated factor (55.9 % vs. 79.0 %, p = 0.002).