“…1 and eTable S1, http://links.lww.com/EJA/A926). Thirty-five studies had a parallel randomised design 13–19,21,23,25–31,33,34,36,38–40,43–57,62,63 ; 12 had a crossover randomised design 20,22,24,32,35,37,41,42,58–61 . Only five studies were multicentre investigations 23,33,36,38,39 .…”