Easton et al. BMC Public Health 2010, 10:459 http://www.biomedcentral.com/1471-2458/10/459 asked whether parents knew the date of their next well child appointment. People with low literacy skills may be more likely than those with high literacy skills to memorise appointment dates (rather than rely on check- ing appointment letters or diaries) to ensure they keep them, and so more likely to score well on this question. The lower likelihood of access to a particular treatment such as antiretroviral medication [27] may be associated with patient-provider relationships; poorer communica- tion or diminished self-efficacy in gaining treatment among patients with low health literacy. However, none of these issues have been studied and it is not clear whether broader aspects of health literacy such as moti- vation or ability to navigate the health system have been instrumental. Evidence of poorer adherence [36,37] and poorer care of children [38-40] suggests that people with lower health literacy skills may be less likely to adopt effective health promoting or self-care behaviour. This may not be related directly or exclusively to difficulty with read- ing and following instructions. Subjective physician assessment of patient health literacy was a significant predictor of failure to attend follow up for treatment [24] and although there was a high correlation between their assessment and objective measures of health lit- eracy, physicians did not correctly assess health literacy levels of all the patients. Some physicians’ predictions may have been based on the assessment of other aspects, such as the degree of engagement, attitude and body language of patients. Although these findings sug- gest that healthcare professionals may be able to assess likely literacy problems among their patients when asked, this is not normally the case in routine practice, as reported elsewhere [14-16]. Qualitative research sug- gested that people with lower health literacy could struggle with some of the methods used to assess treat- ment adherence [41] and this may affect the measure- ment and reporting of adherence studies in general. In examining differences in relationships with health- care staff, it is not clear to what extent these findings reflect differential treatment by staff or differential per- ceptions of treatment by service users. It is possible that people with lower health literacy may respond differ- ently to questions about quality of service or have differ- ent expectations from those with higher health literacy skills [34]. The study of people living with HIV-AIDS who reported differential explanations by doctors about their condition raises the issue that those with lower health literacy may also have reduced opportunities to improve their health literacy [35]. Other studies have identified a range of patient char- acteristics which may impact on those with low func- tional or health literacy accessing services and carrying out self-care activities. Poorer knowledge of health Page 8 of 10 status [27,35] or medication [41] have been reported, but there is no evidence presented here that knowledge of a condition or medication has a direct relationship with adherence to treatment and two studies found that knowledge did not mediate behaviour [30] or adherence [37]. The studies of people with HIV-AIDS all recruited participants through the use of flyers or through provi- ders, which may have led to a degree of self-selection and the results may not apply across the population living with HIV-AIDS [27,35,36,44]. Emotional responses and/or diminished self-efficacy may be mediators in the relationship between health lit- eracy and health [29,33,44] and this may include the stigma associated with low health literacy reported else- where, [9] as it has been suggested that higher aware- ness of patient need among healthcare staff may improve patient experience [25]. This review should be interpreted in the context of several considerations. A large number of papers were initially identified. However, considerable proportions were excluded by title or after abstract appraisal. The inclusion of ‘educational status,’ occasionally but not fre- quently used to describe literacy, as a search item, increased the sensitivity of the search but also contribu- ted greatly to the number of papers that were subse- quently excluded. Many of the studies included in this review did not state language eligibility criteria for participants and pri- mary language has been assumed from country and eth- nicity in several papers. In addition, in some of the included studies, participants were required only to be “English speaking,” not to have English as a primary lan- guage. (Additional file 2, Table S2) Ethnicity, used as a proxy for language, is likely to overestimate the propor- tion with language difficulties, particularly in groups where there are second or third generation adults. This has probably resulted in some relevant papers being excluded and an underestimation of the effect in our population of interest. However, this was deemed more appropriate because where language was not explicitly stated we could not assume the population matched our requirements. Similarly, studies which focused on adults over the age of 65 were excluded but many people over this age do not have reduced cognitive skills which impact on literacy skills, so once more some relevant papers may have been excluded. Again, this was deemed appropriate because there was no way of distinguishing among such populations. The studies used different cut-off points to indicate lower or higher functional or health literacy. The effect of this is unknown and it remains unclear what levels of functional or health literacy impact on health and self- care, whether and to what extent there are thresholds and/or gradient effects in different contexts and in