Librarians are usually involved in systematic reviews for a number of reasons: database choice, search strategy development, and search documentation. See for example: The Role of Health Librarians in Systematic Reviews from Dean Giustini at UBC: http://hlwiki.slais.ubc.ca/index.php/The_role_of_health_librarians_in_systematic_reviews or Rethlefsen ML, Murad MH, Livingston EH. Engaging medical librarians to improve the quality of review articles. JAMA. 2014 Sep 10;312(10):999-1000. doi: 10.1001/jama.2014.9263. PubMed PMID: 25203078.