“…After removing duplicates, 700 items were left, of which 482 were excluded on the basis of title and abstract screening, leaving 218 articles (Online Resource 3). Three relevant articles were published after completion of the search: Bondarenko et al (2013) [16], Almenar-Cubells et al (2013) [17] and Volovat et al (2013) [18]; these were included to replace congress abstracts identified by the initial search that described the same studies [19][20][21]. Finally, 33 publications and 11 congress abstracts representing 41 studies were analysed.…”