How effects on health equity are assessed in systematic reviews of effectiveness

Health in all countries of the world is unevenly and, to some extent, unfairly distributed according to socioeconomic position. Health and longevity are highest for the richest, and decrease steadily with decreasing socioeconomic status. Avoidable and unfair inequalities have been termed health inequities. Enhancing health equity has now achieved international political importance with endorsement from the World Health Assembly in 2009.  The failure of systematic reviews to consider effects on health equity is cited by decision-makers as a limitation.  Hence, there is a need for guidance on the advantages and disadvantages of how to assess effects on health equity in systematic reviews.

This review identified thirty-four methodological studies in which collections of systematic reviews were examined.  We identified four methodological approaches to assess the effects on health equity, a descriptive assessment in the reviews, a descriptive assessment of the trials included in the reviews, analytic approaches, and applicability assessment. However, the most appropriate way to address any of these approaches is unclear. There is a need for methodological guidance on how to assess effects on health equity in systematic reviews.  Analysis of particular groups of populations need to be justified and reported in sufficient detail to allow their credibility to be assessed. There is a need for improved transparency of judgments about applicability and relevance to disadvantaged populations.

Authors' conclusions: 

There is a need for improvement in conceptual clarity about the definition of health equity, describing sufficient detail about analytic approaches (including subgroup analyses) and transparent reporting of judgments required for applicability assessments in order to assess and report effects on health equity in systematic reviews.

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Background: 

Enhancing health equity has now achieved international political importance with endorsement from the World Health Assembly in 2009.  The failure of systematic reviews to consider effects on health equity is cited by decision-makers as a limitation to their ability to inform policy and program decisions. 

Objectives: 

To systematically review methods to assess effects on health equity in systematic reviews of effectiveness.

Search strategy: 

We searched the following databases up to July 2 2010: MEDLINE, PsychINFO, the Cochrane Methodology Register, CINAHL, Education Resources Information Center, Education Abstracts, Criminal Justice Abstracts, Index to Legal Periodicals, PAIS International, Social Services Abstracts, Sociological Abstracts, Digital Dissertations and the Health Technology Assessment Database. We searched SCOPUS to identify articles that cited any of the included studies on October 7 2010.

Selection criteria: 

We included empirical studies of cohorts of systematic reviews that assessed methods for measuring effects on health inequalities.

Data collection and analysis: 

Data were extracted using a pre-tested form by two independent reviewers. Risk of bias was appraised for included studies according to the potential for bias in selection and detection of systematic reviews

Main results: 

Thirty-four methodological studies were included.  The methods used by these included studies were: 1) Targeted approaches (n=22); 2) gap approaches (n=12) and gradient approach (n=1).  Gender or sex was assessed in eight out of 34 studies, socioeconomic status in ten studies, race/ethnicity in seven studies, age in seven studies, low and middle income countries in 14 studies, and two studies assessed multiple factors across health inequity may exist.

Only three studies provided a definition of health equity. Four methodological approaches to assessing effects on health equity were identified: 1) descriptive assessment of reporting and analysis in systematic reviews (all 34 studies used a type of descriptive method); 2) descriptive assessment of reporting and analysis in original trials (12/34 studies); 3) analytic approaches (10/34 studies); and 4) applicability assessment (11/34 studies). Both analytic and applicability approaches were not reported transparently nor in sufficient detail to judge their credibility.

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