Easton et al. BMC Public Health 2010, 10:459 http://www.biomedcentral.com/1471-2458/10/459 Inclusion Criteria We considered studies of any design which examined relationships between functional literacy or health lit- eracy (assessed by a validated measure or recognised by attendance at an adult literacy program) and health out- comes or health-related knowledge or behaviours in a working age population whose first language was the dominant language of their resident country. A full list of inclusion and exclusion criteria is included in Addi- tional file 1, Table S1. Search strategy We searched for relevant studies in two stages, looking first at studies that had been included in previous, read- ily identifiable reviews of functional or health literacy and then applying a sophisticated supplementary search strategy to relevant electronic databases. The first search for readily identifiable reviews was conducted using the key terms “health” AND “literacy” AND “review” in MEDLINE, CINAHL, British Nursing Index, EMBASE, ERIC and PsycINFO. The second search strategy, which was used to check for any relevant studies that had not been included in previous reviews, covered the following databases: MEDLINE 1950 - December 2008; CINAHL 1982 - December 2008; British Nursing Index 1994 - December 2008; EMBASE 1980 - December 2008; ERIC 1965 - December 2008; PsycINFO 1967 - December 2008; and ASSIA 1987 - December 2008. The search comprised key terms associated with the inclusion criteria, tailored for each electronic database. Although some search terms were common to all search strategies, adjustments were made to take advantage of the different indexing terms available within individual databases, and to add a health focus to those databases that did not have this by default. In order to ensure that as many studies as possible were identified, the search strategy was designed to have high sensitivity even though this would likely be at the cost of reduced specificity. A key contributor to this was the decision to include studies indexed by the term ‘educational status’ even though most of these studies related to years of schooling. Abstract appraisal was car- ried out by PE; VE and BW appraised a 10% random sample. Full text appraisal was carried out by PE and one third of papers retrieved for full text appraisal were assessed by all three reviewers; VE and BW carried out independent appraisal of any other papers about which there was uncertainty over inclusion. Data extraction Data relating to study design, populations, sampling, functional or health literacy levels and health outcomes were systematically extracted from each paper by PE. Page 3 of 10 Key findings are presented in Additional file 2, Table S2. Differences were considered to be statistically significant at p < .05. Statistically significant findings are reported numerically; otherwise, results are reported as not signif- icant, even if the authors of the particular study consid- ered this level to be statistically significant. We extracted data relating to the following indicators of research quality: response rate; whether the person mea- suring the health outcome was blinded to participants’ health literacy scores; whether confounding was addressed. Due to the highly diverse nature of populations and health outcomes investigated, differing health literacy measures and cut-off points to make comparisons, we undertook a narrative synthesis of findings. Results A total of 24 relevant papers were included in the review. The initial stage of the search strategy identified four reviews that focused on health outcomes among our age groups of interest [17-20]. Of the 57 primary studies included within these four reviews, 11 met our inclusion criteria. The second stage of the search strategy identified 2400 citations. Figure 1 shows the number of documents excluded at each stage. Additional reviews identified at this stage were also searched for primary papers not No. citations after duplicates removed 2400 Full text papers obtained 217 Included for data extraction 24 Figure 1 Identification of studies 1219 excluded by title 964 excluded after abstract appraisal 178 excluded after full text appraisal 16 reviews 1 additional paper from reviews