IFNL3 and infection: Previous trials showed that monitoring of RBV concentrations at weeks 4, 12, 24 (reviewed in [20]) or at treatment end [21] was associated with higher cure rates, while other studies only found a correlation of RBV concentration and increased response rates in difficult-to-treat patient groups, including GT 1 and 4 infections [6, 17], GT 1 coinfected patients with CT/TT IL28B genotypes [18], and African Americans with the CT/TT genotypes [22].