Fitzpatrick-Lewis et al. BMC Public Health 2011, 11:638 http://www.biomedcentral.com/1471-2458/11/638 Background Each year approximately 160,000 individuals in Canada are homeless [1]. Homelessness can be experienced across genders, age groups, marital status or family com- position, as well as among immigrants and life-long citi- zens of a country [2]. There is no common definition for homelessness, and it remains a challenge to enumerate this population. Homelessness can be hidden; there are estimates that among the “homeless” population, as many as 80% are not experiencing absolute homelessness yet are marginally housed in substandard unsafe housing, are at risk of being evicted, or spend more than 60% of their monthly income on housing [1]. Many homeless people “couch surf” or temporarily sleep in the homes of friends or relatives [3]. Being homeless negatively impacts health as people who are homeless or marginally housed have less access to healthcare and poorer health out- comes than those living in stable housing [3]. There is a lack of awareness and implementation of interventions that have been demonstrated to positively impact health and housing status in people who are homeless. Research on interventions to improve the health of homeless people has received significant attention over the past 5 years. Policy agendas have placed increasing emphasis on poverty reduction strategies and addressing the social determinants of health [4]. Homeless persons have been identified as a priority population within both health policy and practice environments [4,5]. This review stands to inform public health agencies engaging in health promotion and policy development activities with these local priority populations. In 2005, Hwang et al. published a systematic review examining interventions that can increase access to healthcare for homeless individuals [6]. This review included 45 studies of good or fair quality conducted between 1988 and 2004. At the time, this review identi- fied case management and assertive case management as being effective in improving psychiatric symptoms. Case management was also found to be effective in decreasing substance use for homeless persons with substance abuse issues. The current review was conducted at the request of a local public health department seeking an expedited review of the literature pertaining to home- lessness and access to health, healthcare, and housing. This review identifies new research on the impact of interventions on health and health care access for home- less individuals since the review by Hwang and collea- gues [6], with specific focus on the impact of these interventions on their housing status. Methods A protocol for this study has not been previously published. Page 2 of 14 Data Sources For this review PsycINFO, OVID MEDLINE, OVID HealthStar, CINAHL and Sociological Abstracts were searched for the dates January 2004 to December 2009. The initial search was conducted by a skilled and experienced public health librarian using the key search words including: homeless*1, effect*, efficacy, evaluate*, evidence, impact, and outcome*. For a complete list of the search terms see Appendix A (additional file 1). The reference lists of included articles and grey literature were searched for additional relevant articles. The grey literature search was conducted through key relevant websites (e.g., the Public Health Agency of Canada, IntraSpec.ca, PovNet.org, and Health Canada), as well as through the Internet using the Google search engine. Study Selection Titles and abstracts were screened by two reviewers. To establish inter-reviewer reliability, both reviewers inde- pendently screened the first 10% of the titles and abstracts and a Kappa score was calculated, with a Kappa ≥ .80 being considered to be a high level of agreement [7]. Inter-reviewer reliability was very high (Kappa = 0.93) and, as a result, a single reviewer screened the remaining articles at title and abstract stage. All articles that were identified as potentially relevant were included for full relevance testing, e.g., if they included populations that were homeless or at risk of homelessness. Articles were excluded only if abstracts clearly did not include these populations. Two investigators independently rated full-text relevance testing and joined discussions were used to resolve conflicts as necessary. Studies were selected and subsequently quality assessed if they examined the effectiveness of an inter- vention to improve the health or healthcare utilization of people who were homeless, marginally housed, or at risk of homelessness. Intervention effectiveness studies that included homeless populations as a subgroup were also included. Interventions were broadly defined as health or social services delivered in a community set- ting in any country (e.g., services received as an outpati- ent in a primary care setting). Studies were included if they prospectively compared homeless individuals receiving an intervention with those who receive usual care (i.e., no intervention) or a different intervention and examined any relevant outcomes (i.e., health, access to health services, housing status). Retrospective quasi- experimental studies were also included. Acceptable study designs included randomized controlled trials (RCTs), controlled clinical trials, analytic cohort studies (two group pre/post), case control studies, and observa- tional cohorts (one group pre/post). Only English lan- guage articles were included in this review.