During 2009 we searched Medline, EMBASE and
CINAHL without language restrictions for relevant articles
using the search terms ‘‘headache disorders’’ and ‘‘health
care quality’’ for both title and text words. We combined
the individual search results using the Boolean operator
‘‘AND’’. We extended the search to articles containing text
words ‘‘headache care*.tw’’ or ‘‘headache service*.tw’’ in
order to ensure identification of all relevant articles. The
thesaurus terms and text words used for these searches are
shown in Table 1. The search was limited to articles from
1988 onwards, this being the year in which universally
accepted definitions of headache disorders were first published
[8]. We updated the search in February 2012 and
found no new articles specifically related to the definition
of quality or to quality indicators in the context of headache
care. All identified articles were transferred to
Reference Manager, a bibliographic software program.