Concept of a Review Article Satish Bharadwaj What

Concept of a Review Article Satish Bharadwaj

What is a Review Article ? A summary of current status An unbiased critique of the key studies Directions for future research

Why write a review ? to provide up-to-date knowledge on a topic of interest Impractical to read all of the published papers available. (time, accessibility, etc. )

Types of Review Articles Narrative Review A descriptive essay of the conclusions of published studies pertaining to a specific topic / approach published within a certain period more common in basic sciences Expert opinions, “state of the science” Recent advances in a specific field

Types of Review Articles (contd. ) Systematic Review A scientific method of summarizing literature on a specific topic Frequently used in the field of medicine Specific protocols to determine which studies will be included Designed to minimize biases and errors Useful to take informed decision

Systematic Review “A review that is conducted according to clearly stated, scientific research methods, and is designed to minimize biases and errors inherent to traditional, narrative reviews. ” Margaliot, Zvi, Kevin C. Chung. Systematic Reviews: A Primer for Plastic Surgery Research. PRS Journal. 120/7 (2007)

Systematic Review (contd. ) Significance Clinicians and researchers rely on systematic reviews in order to make an informed decision Reviews minimize bias - specific protocols are used to determine which studies will be included in the review

Systematic Review (contd. ) Necessity High volume of published material Variety of common conditions Individual studies report conflicting conclusions - small patient samples and retrospective designs of studies

Systematic Review (contd. ) The process Formulate a Question Conduct Literature Search Refine the search - inclusion and exclusion criteria Extract appropriate data Assess the quality and validity data / method Synthesize the data Interpret and report results of the study

Illustration of Systematic Review Caries Removal Techniques: Conventional vs. Chemomechanical Systems

Hypothesis “ A systematic review should be based on principles of hypothesis testing, and the hypotheses must be conceived a priori ” Make statement(s) regarding unknown population parameter values based on sample data ‘New drug or treatment method is better than the existing one’ Prove or disprove the hypothesis based on the review process

Hypothesis (contd. ) The structured question will determine the search strategy and inclusion-exclusion criteria What is the population of interest? What are the interventions? What are the outcomes of interest? What study designs are appropriate?

Literature search, strategy “A comprehensive and reproducible literature search is the foundation of a systematic review. ” Prone to confusion and bias Can not afford to miss out on studies Keep track of the search terms, sources Record and save search processes

Literature search - challenges Database Bias No single database is likely to contain all published studies on a given subject Publication Bias Selective publication of articles that show positive treatment effects and statistical significance Search for unpublished studies

Literature search - challenges English-language Bias Reviewers exclude papers published in languages other than English Citation Bias Studies with significant or positive results are referenced in publications, compared to studies with inconclusive or negative findings

Inclusion – Exclusion criteria Based on the study question A comprehensive list of inclusion and exclusion criteria Avoid selection Bias Criteria should be agreed upon and formalized before data extraction and analysis

Flow chart of the Search Process

Data Extraction Procedure decided a priori, by consensus during the design stage of the study. Collected data includes: Study characteristics Sample demographics Outcome data

Data Extraction (contd. ) Design a review-specific data extraction form, so that the same data are extracted from each study and missing data are clearly apparent Should be performed by at least two independent readers Validity of a systematic review - ultimately depends on the scientific method of the retrieved studies and the reporting of data

Data Extraction (contd. )

Data Quality and Validity Randomized Controlled Trials (RCT) are considered to be more rigorous than observational studies A review based on well-designed RCT will likely be more valid and accurate than a review based on observational studies or case reports

Data Quality and Validity (contd. ) assess and report study quality - composite, numerical scoring methods > 35 different quality assessment tools - most are designed for RCTs Jadad score and the T. C. Chalmers score - points for use of and reporting randomization, double blinding, withdrawals

Data Synthesis Extracted data are pooled and presented as summary outcome or effect Heterogeneous data - qualitatively - Data that are very conflicting and widely variable should not be combined numerically

Data Synthesis (contd. ) Heterogeneous data – qualitative - can not be combined

Data Synthesis (contd. ) Homogeneous data – quantitative synthesis - When sufficient data, of good quality and homogenous data is available For example: the patients, interventions and outcomes in each of the included studies are sufficiently similar

Meta Analysis A statistical technique for combining the results of independent, but similar, studies to obtain an overall estimate of treatment effect Many protocols available – standardized, guidelines for reporting of meta analysis Statisticians and Epidemiologists

Meta Analysis (contd. ) Validity of a meta-analysis depends on the quality of the studies included Inclusion and exclusion criteria for studies at the design stage Keep track of the studies included and excluded at each step, to document the selection process A flow diagram of the selection process

Flow chart of the Exclusion Process 30 Studies - 2 Studies Older/New gel used - 1 Study Radiography - 4 Studies Inadequate design - 1 Study Use of hand tools - 3 Studies Papacarie technique - 1 Study Extreme heterogeneity - 2 Studies Inadequate reporting 16 Studies

Meta Analysis (contd. ) Data types - Study design, descriptions of study groups, diagnostic information, treatments, length of follow-up evaluation and outcome measures The data should be converted to a uniform metric for pooling - Ex. Calculation of Mean ± SD

Meta Analysis (contd. ) Meta-analysis: combining the results of many clinical studies, evidence generation Two statistical models used: 1. Fixed effects 2. Random effects

Fixed Effects Model The true effect of treatment is the same for every study

Random Effects Model The true effect estimate varies for each study

Results of a Meta Analysis Forest plot - results from each individual study and combined effects calculated using the two models Funnel plot - heterogeneity in data Overall summary statistic Sensitivity analysis Meta-regression, if performed

Forrest Plot Rotor Carisolv

Funnel Plot

Guidelines for Writing a Review Write a short and concise Introduction - to facilitate readers from different backgrounds Describe the current status of research Clearly state the objective of the review

Guidelines for Writing a Review In the Methods section, delineate - clearly the literature search strategy - criteria for inclusion-exclusion of studies - data extraction and validation methods Synthesize Results from various papers and meta analysis to build a coherent argument

Guidelines for Writing a Review Build your Discussion logically using outlines or headings Point out how you have satisfied the objective(s) of your review Cite original References of studies included as well as excluded from the review

Thank you !