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Literature search

Ma. Lucila M. Perez, MD, MSc

� Decide on a specific topic for your study Decide on a specific topic for your study Decide on a specific topic for your study Decide on a specific topic for your study

: : : : ALWAYS WRITE THE RQ IN P-E-(C)-O FORMAT

EX. ANO ANG EPEKTO NG GATAS SA PAGIGING OBESE EX. ANO ANG EPEKTO NG GATAS SA PAGIGING OBESE EX. ANO ANG EPEKTO NG GATAS SA PAGIGING OBESE EX. ANO ANG EPEKTO NG GATAS SA PAGIGING OBESE NG BATA?NG BATA?NG BATA?NG BATA?

RQ: Among children children children children (P)(P)(P)(P)(P)(P)(P)(P), will intake of Lower Lower Lower Lower ----ProteinProteinProteinProteinFormulaFormulaFormulaFormula (E)(E)(E)(E)(E)(E)(E)(E) during infancyuring infancyuring infancyuring infancy as compared to Standardas compared to Standardas compared to Standardas compared to Standardas compared to Standardas compared to Standardas compared to Standardas compared to StandardFormula Formula Formula Formula Formula Formula Formula Formula (C)(C)(C)(C)(C)(C)(C)(C) aaffect risk for obesity obesity obesity obesity (O)(O)(O)(O)(O)(O)(O)(O)????

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OUTLINE :

� WHY we should look

� WHAT to look for

� WHERE to look

� HOW to look

� It helps elaborate the research problem in relation to relevant literature

� Lays out : ◦ KEY IDEAS related to your research

◦ RELATIONSHIPS and IMPORTANCE of key ideas

◦ What is known and UNKNOWN

◦ Your CONTRIBUTION and how your research is JUSTIFIED

◦ Shows you understand your field

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� Literature search content includes:

◦ Magnitude of the problem under study

◦ Present state of knowledge on the problem� What has been studied

� Areas of controversy

� Unanswered questions

Sources of information:Sources of information:Sources of information:Sources of information:� Published◦ Journal articles

◦ Books

◦ Proceedings (Abstracts)

◦ Internet

� Unpublished◦ Thesis, dissertations

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� HAND SEARCH

� INTERNET SEARCHe-Literature Databases:

� Pubmed

� Embase (Excerpta Medica Database)

� Herdin

� Cochrane

� Ovid

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DOING EFFICIENT eDOING EFFICIENT eDOING EFFICIENT eDOING EFFICIENT e----LITERATURE SEARCHLITERATURE SEARCHLITERATURE SEARCHLITERATURE SEARCH

STEPS:

1. Rank concepts according to importance

2. Expand the most important concepts

3. Intersect concepts according to ranks

4. Examine the yield

1. RANK THE CONCEPTS (VARIABLES) 1. RANK THE CONCEPTS (VARIABLES) 1. RANK THE CONCEPTS (VARIABLES) 1. RANK THE CONCEPTS (VARIABLES) ACCORDING TO IMPORTANCEACCORDING TO IMPORTANCEACCORDING TO IMPORTANCEACCORDING TO IMPORTANCE

P = ChildrenE = Lower Protein Formula

C = Standard FormulaO = ObesityM = Meta-analysisM = Randomized Clinical Trial (RCT)

RQ: Among children children children children (P)(P)(P)(P)(P)(P)(P)(P), will intake of Lower Lower Lower Lower ––––Protein FormulaProtein FormulaProtein FormulaProtein Formula (E)(E)(E)(E)(E)(E)(E)(E)during infancyuring infancyuring infancyuring infancy as compared to Standard Formula as compared to Standard Formula as compared to Standard Formula as compared to Standard Formula as compared to Standard Formula as compared to Standard Formula as compared to Standard Formula as compared to Standard Formula (C)(C)(C)(C)(C)(C)(C)(C) aaffectrisk for obesity obesity obesity obesity (O)(O)(O)(O)(O)(O)(O)(O)????

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2. EXPAND THE MOST IMPORTANT 2. EXPAND THE MOST IMPORTANT 2. EXPAND THE MOST IMPORTANT 2. EXPAND THE MOST IMPORTANT CONCEPT CONCEPT CONCEPT CONCEPT TO ACCOUNT FOR TO ACCOUNT FOR TO ACCOUNT FOR TO ACCOUNT FOR VARIATIONS IN VARIATIONS IN VARIATIONS IN VARIATIONS IN TERMINOLOGYTERMINOLOGYTERMINOLOGYTERMINOLOGY

I. I. I. I. Free Text SearchFree Text SearchFree Text SearchFree Text SearchII. II. II. II. MeSH SearchMeSH SearchMeSH SearchMeSH Search

A. 1. Hypoprotein Milk Formula2. Low Protein Milk Formula3. Low Protein Milk Formulation

B.1. Obesity2. Overweight

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ENTER TERMS ONE ENTER TERMS ONE ENTER TERMS ONE ENTER TERMS ONE BY ONE HEREBY ONE HEREBY ONE HEREBY ONE HERE

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NUMBER OF NUMBER OF NUMBER OF NUMBER OF ARTICLES ON TOPICARTICLES ON TOPICARTICLES ON TOPICARTICLES ON TOPIC

= Medical subheadings

◦ List of 177,000 concepts◦Organized in a complex hierarchy called“MeSH Tree”◦More specific as more branches

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ADV DISADV

FREETEXT

New terms Long strategy;Subject to user error

MeSH Shorter Unlisted terms;Subject to Clerical errors;Evolves

3. COMBINE THIS SEQUENTIALLY WITH 3. COMBINE THIS SEQUENTIALLY WITH 3. COMBINE THIS SEQUENTIALLY WITH 3. COMBINE THIS SEQUENTIALLY WITH OTHER CONCEPTS (AS RANKED)OTHER CONCEPTS (AS RANKED)OTHER CONCEPTS (AS RANKED)OTHER CONCEPTS (AS RANKED)

� BOOLEAN LOGIC OPERATORS

• ANDAND – each citation contains all the search terms; INTERSECTION

• OROR - each citation contains at least 1 of the search terms; UNION

• NOTNOT - excludes retrieval of term from the search

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1 6

2 3 5 9

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10 11

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BB(LOW PROTEIN MILK FORMULA)

AA(OBESITY)

CC (CHILDREN)

A OR BA OR B

A AND BA AND B

B AND CB AND C

1, 2, 3, 4, 5, 6, 7, 8, 9

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5, 9

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4. EXAMINE YIELD FOR HITS AND MISSES AND 4. EXAMINE YIELD FOR HITS AND MISSES AND 4. EXAMINE YIELD FOR HITS AND MISSES AND 4. EXAMINE YIELD FOR HITS AND MISSES AND MODIFY SEARCH IF NEEDEDMODIFY SEARCH IF NEEDEDMODIFY SEARCH IF NEEDEDMODIFY SEARCH IF NEEDED

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4. EXAMINE YIELD FOR HITS AND MISSES 4. EXAMINE YIELD FOR HITS AND MISSES 4. EXAMINE YIELD FOR HITS AND MISSES 4. EXAMINE YIELD FOR HITS AND MISSES AND MODIFY SEARCH IF NEEDEDAND MODIFY SEARCH IF NEEDEDAND MODIFY SEARCH IF NEEDEDAND MODIFY SEARCH IF NEEDEDAND MODIFY SEARCH IF NEEDEDAND MODIFY SEARCH IF NEEDEDAND MODIFY SEARCH IF NEEDEDAND MODIFY SEARCH IF NEEDED

� If TOO FEW :1. Broaden your question

2. Find more search terms

- use MeSH instead of Free text;

- Free text instead of MeSH;

- Get union of MeSH & Free text

3. Use truncation (* ) or wildcard (?) in Free Text

� If TOO MANY :1. Intersect more concepts (use AND)

2. Narrow your question

3. Use more stringent method filters :

NOT or NEAR

Use LIMITS

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LIMITS IN PLACELIMITS IN PLACELIMITS IN PLACELIMITS IN PLACE

� Have a clear idea of your RQ

� Decide on what information is needed

� Do both internet-search and hand search

� Do efficient e-search whether by free text or MeSH

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