Once- versus twice-daily abacavir and lamivudine in African children: the randomised controlled ARROW Trial by Musiime, V, Kasirye, P, Naidoo-James, B, Nahirya-Ntege, P, Mhute, T, Cook, A, Mugarura, L, Munjoma, M, Thoofer, N, Ndashimye, E, Nankya, I, Spyer, M, Thomason, M, Snowden, W, Gibb, D, Walker, A, ARROW Trial Team