https://www.ncbi.nlm.nih.gov/pubmed/27101467#cm27101467_65245 (PubMed Commons comment; now removed)

I thank the authors for including the full version of their search strategies in the appendix. This is a valuable tool for readers to more comprehensively analyze the systematic review's methodology and outcomes. In the appendix containing the full search strategies, the MEDLINE search and the Embase search appear identical. It is unclear if these databases were searched simultaneously using Ovid's multifile searching capability, or whether the search listed for MEDLINE is in fact not the search used for the MEDLINE search. It is of course also possible that the same search was used for each database, though searched individually. The primary complication with the MEDLINE search as reported is that many of the search terms used are Embase-specific Emtree terms that are not searchable in MEDLINE. This includes: "crossover procedure"; "double blind procedure"; "single blind procedure"; "triple blind procedure"; "animal"; "nonhuman"; "human"; "human cell"; and "ulcerative colitis." Because these are not the correct MeSH terms for these concepts, searches for these terms as indicated would produce no results. This unfortunately impacts two major components of the search, from the recommended Cochrane Embase sensitive search for randomized control trials (lines 1-18) and the disease state section (lines 21-24). Multifile Ovid searching does try to map thesaurus terms to corresponding thesaurus terms across databases, which may resolve some of these issues. However, a best practice would be to include both Emtree and MeSH terms in a search instead of relying on multifile term mapping. If the authors did rely on multifile searching, it would be appropriate to note this in the methods section to alert readers. In addition, lines 26 and 27 both search for the MeSH heading "Mesalamine," and lines 28 and 29 both search for the MeSH heading "Sulfasalazine." This was perhaps adapted from the previous version of this review (Feagan BG, 2012), which also utilizes this duplication. It is not clear why these terms were duplicated in either case, though this version of the review did update the rest of the search strategy to be more comprehensive and also more specific.