Narrative Literature Reviews Versus Systematic Reviews

HETEROGENEITY

In systematic reviews, differences in the results of individual studies that are more than a chance occurrence. Cultural, social, biological, or other differences within a group.

Quality of the Systematic review

The VALIDITY of the meta-analysis DEPENDS on the QUALITY OF THE SYSTEMATIC REVIEW on which it is based.

Requirements for meta-analysis

WELL-EXECUTED SYSTEMATIC REVIEW. However competent the meta-analysis, if the original review was partial, flawed or otherwise unsystematic, then the meta-analysis may provide a precise quantitative estimate that is simply wrong.

Systematic Review is

a strict approach (i.e. clear set of rules used for identifying studies); which includes the use of an accurate search strategy in order to identify all studies addressing a specific topic, the establishment of clear inclusion/exclusion criteria and well-defined methodological analysis of the selected studies.

Meta-analysis

a systematic review ALWAYS proceeds a meta-analysis. A statistical technique that involves combining and analyzing the results of many research studies on a specific topic in order to identify overall trends.

Narrative review is

generally based on a subjective selection of publication through which the reviewer qualitatively addresses a question summarizing the findings of previous studies and drawing a conclusion.

Disadvantages of Narrative review

1. authors bias 2. no clear methodology (the identification of the literature is not transparent) 3. lack of specific search strategy = risk of failing to identify relevant or key studies on a given topic 4. questions about the conclusions made by the authors 5. should be considered opinion pieces more than evidence based.

Good meta-analysis

A good meta-analysis aim for COMPLETE COVERAGE of all RELEVANT STUDIES, look for the presence of HETEROGENEITY, and explore the robustness of the main findings using SENSITIVITY ANALYSIS.

SENSITIVITY ANALYSIS

Many judgments are required in the process of preparing a meta-analysis. Sensitivity analyses should be used to examine whether overall findings are robust to potentially influential decisions.Testing the robustness of the results of a model or system in the presence of uncertainty.

Clinical effectiveness

Meta-analysis is most often use to assess the CLINICAL EFFECTIVENESS OF HEALTHCARE INTERVENTIONS; it does this by combining data from two or more randomized control trials.

Treatment effect

Meta-analysis of trials provides a PRECISE ESTIMATE OF TREATMENT EFFECT, giving due weight to the size of the different studies included.

Conducting meta-analysis

NEEDS: location of studies, quality assessments, calculating effect size, checking for publication bias,

Search Strategy

Narrative = Not described Systematic = Clearly defined

Selection of the studies

Narrative = Not described Systematic = Clearly defined

Analysis of the studies

Narrative = Not described Systematic = Clearly described

Ranking of studies

Narrative = Not performed Systematic = By levels of evidence

Methodology

Narrative = Not, or insufficiently described Systematic = Clearly defined

Research question

Narrative = broadly formulated Systematic = Strictly formulated

Literature review can be...

Narrative or systematic