Realizing effectiveness across continents with hydroxyurea: enrollment and baseline characteristics of the multicenter REACH study in Sub-Saharan Africa by McGann, PT, Williams, TN, Olupot-Olupot, P, Tomlinson, GA, Lane, A, Luís Reis da Fonseca, J, Kitenge, R, Mochamah, G, Wabwire, H, Stuber, S, Howard, TA, McElhinney, K, Aygun, B, Latham, T, Santos, B, Tshilolo, L, Ware, RE