Acceptability and usability of oral fluid HCV self-testing among health-facility users from Brazil: a cross-sectional study of 685 participants Hugo Perazzo; Cristiane Villela-Nogueira; Maria K. Gomes; Andre Daher; Cristiane Siqueira-do-Valle; Ketiuce Zukeram; Ana Cristina G. Ferreira; Karen Cristine Tonini; Elton Carlos de Almeida; Sandra W. Cardoso; Beatriz Grinsztejn; Valdilea G. Veloso;