1. How to search the medical literature on the net
Samir Haffar M.D.
Associate Professor of Gastroenterology

2. My students are dismayed when I say to them
“Half of what you are taught as medical students
will in 10 years have been shown to be wrong.
And the trouble is, none of your teachers knows
which half.”
Dr Sydney Burwell
Dean of Harvard Medical School

3. Background questions
• Sometimes
Involve a single fact such as:
“What is the causative agent of Chagas disease?”
“What is the hemophagocytic syndrome? ”
• Often
Involve much more information such as:
“How do I insert a jugular venous central line?”

4. Searching background questions
Easy to search
• Standard textbooks such as Harrison, Nelson….
• Innovative electronic texts such as UpToDate
• Some companies group collections of textbooks
MDConsult http://www.mdconsult.com/
Stat!Ref http:// www.statref.com/
• Entry of single concept such as disease or diagnostic test

5. Textbooks
Textbooks may be a useful source of information
on “background” questions but:
• May provide biased advice
• Rapidly become out of date

6. • Very popular with generalists, specialists, & house staff
– Ease of use
– Comprehensiveness
– Inclusion of disease-oriented formation
• Provides recommendations (guidelines) for clinicians

7. • Questions that provide the evidentiary basis for specific
clinical decisions
• Best structured using the framework of:
- Patient
- Intervention
- Comparison (if relevant)
- Outcomes
Foreground questions
PICO/PIO

8. What is the best evidence?
• The best evidence is the evidence most likely to
provide an unbiased view of the truth
• Bias is difference between study results & truth
• Of course, we can never know the truth, but we can
try to come as close as possible by performing &
using well-designed & well executed studies

9. Level of evidence
Oxford Centre of EBM
Levels of
evidence
Bias
Bias
Bias
Bias
Bias
Bias
Validity/StrengthofInference

10. Example of PICO/PIO Concept
• 70-year-old man with PUD & stable angina tt by low-
dose aspirin, statin, ACE inhibitor & nitrates as needed
• The patient developed recently an UGI bleeding
UGI endoscopy revealed no ulcer & biopsy was – for HP
• You wonder if clopidogrel is more effective than the
association of PPI & asipirin for recurrent PU bleeding

11. Key components of your clinical question
PICO
P
I
C
O
Patient Elderly patient with aspirin-associated PU
Intervention Clopidogrel
Comparaison PPI + Aspirin
Outcome Recurrent PU bleeding
Good question should have 3 or 4 components

12. Formulation of the relevant question
In a elderly patient with aspirin-associated PU,
is clopidogrel more effective than PPI & aspirin
to prevent recurrence of PU bleeding?

13. The amount of medical literature
0
500000
1000000
1500000
2000000
2500000
Biomedical MEDLINE Trials Diagnostic
MedicalArticlesperYear
5,000
per day
1,500
per day
95 per
day
55 per
day
Glasziou P, Del Mar C. Evidence based practice workbook.
Blackwell Publishing, 2nd edition, 2007.
So much evidence, so little time

14. How can I find what I am searching for?

15. • Interface to MEDLINE (NLM*) & easiest way to use it
• From 1950 to date
• 19 million articles as of November 2009
• Growing at rate of 700 000 articles/year
• ≈ 5 000 indexed journals
• > 70 million search done each month
• Search terms by topics, authors or journal
Free on the Internet since the mid-1990s
* US NLM: United States National Library of Medicine

16. Annual addition of articles to PubMed
50 years ago Majority of research not published in English
Currently Almost 90% of articles published in English

17. PubMed tutorial
• Side bar of the PubMed entry page
• Quite detailed tutorial program
• Takes about 2 hours to go right through
• Very helpful

18. PubMed Tutorials
http://www.ncbi.nlm.nih.gov/

19. MeSH Database

20. Text word & MeSH term*
• Text word
Any word or phrase in the title or abstract of an article
• MeSH terms
Vocabulary used to index all MEDLINE articles
• Example:
“hemorrhage” [Text Word]
“haemorrhage” [Text Word]
“hemorrhage” [MeSH Terms]
* MeSH: Medical Subject Headings in PubMed

21. Tree structure of MeSH in PubMed
The „explode‟ (exp) feature of tree structure allows to
capture entire subtree of MeSH* terms within single word
One of 3 MeSH categories of peptic ulcer
* MeSH: Medical Subject Headings in PubMed

22. Alternative spellings & misspellings
(a) hemorrhage American spelling
[Mesh term]
(b) haemorrhage British spelling
(c) hemorhage Misspelling
(d) haemorhage Misspelling

23. Boolean operator ‘OR’
After its creator George Boole
Akobeng AK. Arch Dis Child 2005 ; 90 : 837 – 840.

24. Akobeng AK. Arch Dis Child 2005 ; 90 : 837 – 840.
Boolean operator ‘AND’
After its creator George Boole

25. Akobeng AK. Arch Dis Child 2005 ; 90 : 837 – 840.
Boolean operator ‘NOT’
After its creator George Boole

26. Boolean search
After its creator George Boole
Boolean operators Meaning
Peptic ulcer OR Hemorrhage
Peptic ulcer AND Hemorrhage
Peptic ulcer NOT Hemorrhage

27. ‘Wildcards’
malig* means malignancy
malignant
malign
but not malunion
malaligned
etc

28. PubMed command – 1
Command What it does?
OR Finds articles containing either of specified words
Ex: child OR adolescent
AND Finds articles containing both specified words
Ex: child AND adolescent
NOT Excludes articles containing the specified word
Ex: child NOT adolescent
Glasziou P, Del Mar C. Evidence based practice workbook.
Blackwell Publishing, 2nd edition, 2007.
Limits Articles restricted in several ways by: date, language, age, …
( ) Use parentheses to group words
Ex: (colorectal cancer) AND (screen AND mortality)

29. PubMed command – 2
Command What it does?
*
Truncation
Acts as a wildcard indicating any further letters
Ex: child * = (child OR childs OR children OR childhood)
Glasziou P, Del Mar C. Evidence based practice workbook.
Blackwell Publishing, 2nd edition, 2007.
[ti] Finds articles with the word in title
Ex: ulcer [ti] = find article with the word ulcer in title
[so] or so Find articles from a specific source
Ex: ulcer AND BMJ [so] = finds articles on ulcer in BMJ
MeSH Controlled vocabulary keywords used in also in Cochrane
Often useful to use both MeSH heading & text words

30. PubMed translation of query into search terms
PICO Element Search terms for PubMed
P Elderly patient
Peptic ulcer
Limit to “aged: 65+ years”
“peptic ulcer” [MeSH term]
I Clopidogrel “clopidogrel” [MeSH term]
C PPI
Aspirin
“proton pump inhibitors” [MeSH term]
“aspirin” [MeSH term]
O Recurrence
Peptic ulcer bleeding
“recurrence” [MeSH term]
“peptic ulcer hemorrhage” [MeSH term]
Other RCT Limit to “randomized controlled trial”

31. PubMed Clinical Queries
• Search faster & more relevant articles
• Category
Etiology, dg, therapy, prognosis, clinical prediction guides
• Search
Narrow specific search
Broad sensitive search

32. PubMed Clinical Queries

33. PubMed Clinical Queries

35. N Engl J Med 2005 ; 352 : 238 – 44.
Clopidogrel vs aspirin & esomeprazole
Difference 7.9 % points
95 % CI: 3.4 – 12.4
P = 0.001 by log-rank test

36. Aspirin plus esomeprazole was superior to
clopidogrel in the prevention of recurrent
ulcer bleeding.

37. How to improve your PubMed search?
• “Related Articles” link
• Select another set of terms & try again
• “AbstractPlus” format
• “Limits” link: sex, age, language, RCT,…
• “MeSH” terms: Medical Subject Headings

38. Related articles link

39. “Limits” link

40. “Limits” link

41. Question type & study design
Study DesignQuestion
Intervention RCT
Incidence & prognosis Cohort study
Prevalence Cross-sectional study
Etiology & risk factors Cohort or case-control
Diagnosis Cross-sectional study
In each case, SR of all available studies better than individual study

42. How many questions can doctors answer each day?
64 residents in 2 hospitals
401 consultations
280 questions (2 for 3 patients)
80 answers (29%)
Sources of answers:
– Textbooks (31%)
– Articles (21%)
– Consultants (17%)
Green ML et al.
Am J Med 2000;109:218–233.
Residents
103 GPs
Questions collected over 2.5 d
1101 questions
702 answers (64%)
Sources of answers:
– Available print
– Human resources
– Literature search: 2 answers
Ely JW et al.
BMJ 1999;319: 358–361.
GPs

43. 1- Ask
2- Acquire
4- Apply
5- Assess
Patient
dilemma
Principles
of EBP
Evidence alone does not
decide – combine with other
knowledge & values
3- Appraise
Hierarchy
of evidence
5 A

44. 50,000 articles/yr
from 120 journals
~3,000 articles/yr
meet critical appraisal
& content criteria
(94% noise reduction)
McMaster PLUS project – First level
Critical appraisal filters
 Valid
 Ready for clinical attention
Health Information Research Unit – McMaster University – Canada

45. High quality/relevant data – Pearls
Glasziou P, Del Mar C. Evidence based practice workbook.
Blackwell Publishing, 2nd edition, 2007.
Finding high-quality evidence like searching for „rare pearls‟

46. High quality/relevant data
Pearls
If not valid No value
If not relevant No value

47. Steps
– Answerable question
– Search
– Appraise
– Apply
EBM & Systematic Review
Find a systematic review
Steps
– Answerable question
– Search ++++
– Appraise x 2
– Synthesize
– Apply
Time: 6 months – Team
2 000 articles
This patient dies
Systematic reviewEBM
Time: 90 seconds
< 20 articles
This patient survives

48. Limitations of evidence
• Evidence simply doesn‟t exist
• Some of what is available
Not easily accessible
Not clinically relevant
Not of good quality
Not applicable to your patient
It takes time to develop high quality evidence
& more time to get it to publication

49. Learning through play
• Try all “buttons”
• Make lots of “mistakes”
• Have fun

50. Thank You