“…While on the one hand, a search for unpublished studies may allow systematic reviewers to be comprehensive and mitigate the impact of publication bias (McAuley et al, 2000), on the other hand, there are legitimate concerns about whether studies available only as conference abstracts ('abstracts') should be included at all in systematic reviews (Dundar et al, 2006;Saldanha et al, 2016). The concerns mainly arise because: (1) it may be difficult to assess the quality and extract data from the limited information generally available in abstracts (Dundar et al, 2006), and (2) discrepancies between abstracts and full-text publications of abstracts have been described in a number of assessments in different clinical areas (Weintraub, 1987;Chan et al, 2013;Livas et al, 2014;Hopewell et al, 2015;Wieser et al, 2015;Saldanha et al, 2016). Some of the discrepancies might be related to abstracts containing only preliminary data (Mahood et al, 2014).…”