LITERATURE REVIEW: THE WAY TO GET IDEA AND SUPPORT YOUR OPINION Ching-Chih Lee

What is literature review  Synthesis of existing knowledge: not just report previous studies  Acquainted with status-quo (present) knowledge  Explain and justify the formulation of research questions or hypothesis Polished conceptual framework Ref 2 Ref 1 Idea Ext validity Limitations Int. validity Statistics

How to do?  Summarize past research  Explanation of decisions  Punctuated (emphasized) by references  Justify the need for further study:  Find the gap  Find the significance  Start your study

 No difference, No study  NO variation, No study

EBM: Hierarchy of evidence  System: Decision support, guidelines  Summaries: Clinical Evidence (BMJ)  Synopsis( 概要 ): review; DARE database ( Database of Abstracts of Reviews of Effectiveness )  Syntheses( 綜合體 ): Cochrane Database of Systematic Reviews  Studies: medline

Five steps in LR  Determine the major concepts  Prepare the coding sheet  Search for relevant references  Analyze the references  Report previous research on the selected topic

Determine the major concepts  What are the concepts for your question?  List concepts: order of importance; logical presentation  The incidence of NPC in Taiwan  The subsequent risk of stroke in head and neck cancer  The stroke incidence in NPC: remained unknown  ……….  Don’t overlook worthy studies  Search,  analyze  search again…….

Prepare coding sheet (1)  Collect all needed information: Endnote is a good method  Critique the references  A coding sheet is the results of preliminary review:

Prepare coding sheet (2)  Background information  Design information  Measurement information  Outcomes information  Limitations

Search for relevant references (1)  Read extensively in the area that are either area directly or indirectly related to the topic of study  Use current and widely accepted references

Search for relevant references (2)  Sources of literature  Books  Journals: Medline, Pubmed, OVID, Health star…  These  Government reports  Scientific meeting  Unpublished work

Search for relevant references (3)  How to narrow down your search?  Set limits: date of publication, study design, gender, age group…  Focus on review articles  Use related articles  Search the author’s name  Refine search  Pitfalls: self-cited problem, publication bias (only positive results)

Search for relevant references (4)  Which ones to avoid?  Wrong subject matter  Flawed design Study instrument, target population, dataset can’t answer the question Poorly chosen sample Inappropriate control groups Too small sample size  Flawed analysis Statistical procedures not well explained Unsuitable tests

Search for relevant references (5)  How good should we include? (not how many)  Quality is more important: Key references, such as NEJM, JAMA, Neurology, Stroke, CA, JCO, Cancer, Red Journal  Not too many citation to support your idea  Include the most important or influential papers  Literature review is a proxy of your knowledge in this field

Don’t forget “Clinical queries” in pubmed  Clinical study categories  Systematic reviews  Medical genetics

Demonstration of LR  Use Pubmed  Use limitation  Find related articles  Find articles published by the same author  Download citation  Endnote

Examples Increased stroke incidence in NPC patients: A population-based study in Taiwan

Thanks for your attention!