<qa>  What was the primary double-blind study of raltegravir versus placeboThe primary double-blind study of raltegravir versus placebo was extended to 156 weeks and was followed by an open-label raltegravir phase in which continuing participants from both the raltegravir and placebo groups received open-label raltegravir for an additional 84 weeks for a maximum duration of up to 240 weeks. Participants who had viral failure after Week 16 may have received open-label raltegravir until Week 240. 