Evidence based medicineEvidence based medicine

ByBy::

Mohsen DehghaniMohsen Dehghani

MSc Student in EpidemiologyMSc Student in Epidemiology

Isfahan University of Medical SciencesIsfahan University of Medical Sciences

11

Trace back to the development of Trace back to the development of EBMEBM

Evidence based medicineEvidence based medicine

تلفیق بهترین شواهد بدست آمده از تحقیق با •مهارتهای کلینیکی و ارزشهای بیمار.

• David Sackett,

et al. 2000

استفاده دقیق، روشن و عاقالنه از بهترین شواهد •موجود برای تصمیم گیری در مورد مراقبت از یکایک

بیماران.

Best EvidenceBest Evidence

Patient values

Clinical expertise

33

Evidence based medicineEvidence based medicine

• Evidene based practice (EBP)

؟ نیاز داریم EBPچرا به •

44

Evidence based medicineEvidence based medicine

• Archei cochrane,• British epidemiologist, 1972

نوشت:1979او در سال •مطمئنأ انتقادی بزرگ از حرفه ما این است که برنامه ”•

ای برای خالصه کردن منظم و منتقدانه همه کارآزماییهای بالینی مربوط به یک موضوع در رشته های تخصصی و فوق تخصصی مختلف و بازبینی مستمر آنها

نداریم.“

• Cochrane center• Cochrane collaboration• Cochrane library

55

استفاده از کورتیکوستروئیدها در زایمان استفاده از کورتیکوستروئیدها در زایمان زودرسزودرس

• RCT-1972

• 6RCT, 1972 – 89

• Systematic review, 1990

• conclusion

66

PushPush, , PullPull, , …ways to deal with …ways to deal with

too much informationtoo much information

Evidence-Based Information Resources

77

0

2000

4000

6000

8000

1966 1976 1986 1996

Number of articles on Hypertension cited in Medline by Year

Articles

Increasing KnowledgeIncreasing Knowledge

88

The stepsThe steps

1.    answerable questions

2.    Find the best evidence

3.    Critically appraise that evidence for its validity and usefulness

4. Apply the results

5.     Evaluate the performance

99

Acquire the best evidence

Appraise the evidence

Applyevidence to patient care

Assess your patient

Ask clinical questions

EBM MethodEBM Method

1010

Where Clinical Questions Arise FromWhere Clinical Questions Arise From::

• Clinical findings • Aetiology: • Differential diagnosis: • Diagnostic tests: • Prognosis: • Therapy: • Prevention:

1111

Question components : PICO

• What types of Participants?

• What types of Interventions?

• What types of Comparison?

• What types of Outcomes?

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The four elements of well built clinical The four elements of well built clinical

questions:questions: ((PICOPICO))

Patient

Or

problem

InterventionComparison intervention

outcome

Tips for building

Starting with your patient ask

“how would I describe a

group of patients similar

to mine”?

Ask: “Which main

intervention am I considering”?

Ask “What is the main

alternative to compare with

the intervention”?

Ask “What can I accomplish?”

or “What could this exposure

really affect ”?

exampleIn healthy 1 year old infants

Does giving combined MMR

vaccine

When compared to

not giving

Lead to increased

incidence of autism?

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Best EvidenceBest Evidence……

• Journal of evidence based medicine.

• Encyclopedia of clinical evidence

1414

The Evidence PyramidThe Evidence PyramidT

ime S

pen

t in Critical A

ppraisal

Valid

ity/Strength of Inference

1515

Finding the EvidenceFinding the Evidence

systematic reviewsystematic review

1616

Systematic review & Meta-analysesSystematic review & Meta-analyses

تاثیر دریافت مواد غذایی در طول •زایمان بر پیامد مادری زنان باردار:

RCT

ارتباط بین چاقی و سکته مغزی•

درمان با انسولین و خطر ابتال به •سرطان

1717

1818

Overall (I-squared = 83.1%, p = 0.000)

sullivan et al (2009)

iran (2009)

parsons et al. (2007)

tranmer et al1 (2005)

scheepers et al. (2004)

Study

scheepers et al. (2002)

ID

scrutton et al. (1999)

parsons et al. (2006)

kubli et al1 (2002)

0.19 (0.13, 0.25)

0.14 (0.06, 0.22)

-0.24 (-0.53, 0.05)

0.88 (0.60, 1.16)

0.13 (-0.09, 0.35)

0.27 (-0.01, 0.55)

0.32 (0.04, 0.59)

SMD (95% CI)

0.31 (-0.11, 0.73)

0.63 (0.33, 0.94)

-0.34 (-0.85, 0.17)

100.00

63.16

4.66

5.07

8.54

5.22

%

5.18

Weight

2.27

4.35

1.54

0.19 (0.13, 0.25)

0.14 (0.06, 0.22)

-0.24 (-0.53, 0.05)

0.88 (0.60, 1.16)

0.13 (-0.09, 0.35)

0.27 (-0.01, 0.55)

0.32 (0.04, 0.59)

SMD (95% CI)

0.31 (-0.11, 0.73)

0.63 (0.33, 0.94)

-0.34 (-0.85, 0.17)

100.00

63.16

4.66

5.07

8.54

5.22

%

5.18

Weight

2.27

4.35

1.54

0-1.16 0 1.16

PubMed Clinical QueriesPubMed Clinical Queries

1919

PubMed Clinical QueriesPubMed Clinical Queries

2020

PubMed – Key FeaturesPubMed – Key Features

• Clinical Queries– Clinical study by category– Find systematic reviews

• MeSH Database– Synonyms (keywords) to use for your searches– Tutorials

• Comprehensive Limits Option

• “My NCBI” Alert, Storage and Retrieval Option

2121

2222

The Cochrane CollaborationThe Cochrane Collaboration

Preparing, maintaining and disseminatingsystematic reviews of the effects of health care

2323

Cochrane LibraryCochrane Library

• International collaboration• Produces systematic reviews and meta-

analyses of individual studies• DARE• Registry for RCT• Updated regularly• Abstracts are free• http://www.cochrane.org

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The Cochrane Library Total Records at The Cochrane Library Total Records at December 2010December 2010

DatabaseTotal Records

The Cochrane Database of Systematic Reviews (Cochrane Reviews) 6447

Database of Abstracts of Reviews of Effects (DARE)13521

The Cochrane Central Register of Controlled Trials (CENTRAL) 635,167

The Cochrane Methodology Register (Methodology Register)13,721

Health Technology Assessment Database (HTA)8908

NHS Economic Evaluation Database (NHS EED)28,991

About The Cochrane Collaboration and the Cochrane Collaborative Review Groups (About)80 2525

33..        Critically appraise that evidence Critically appraise that evidence for its validity and usefulnessfor its validity and usefulness

          

•1 -pico مطالعه چیست و آیا کامأل مشابه picoشماست؟

- مطالعه چقدر خوب انجام شده است؟2•

- نتایج چه معنی می دهند؟3•

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What is critical appraisal?What is critical appraisal?

• Critical appraisal is the assessment of evidence by systematically reviewing its relevance, validity and results to specific situations.

Chambers, R. (1998).

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Three questionsThree questions

• Valid?Is the methodology appropriate to answer the question.

Is it carried out in a sound way, eliminating bias and confounding?

• Reliable?Are the results real or because of chance?

• Applicable?Will the results help locally?

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2929

Dealing with chance errorDealing with chance error

• During design of study– Sample size– Power

• During analysis (Statistical measures of chance)– Test of statistical significance (P value)– Confidence intervals

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95% Confidence Interval 95% Confidence Interval (95% CI)(95% CI)

• 20 out of 100 participants: 20%

95% CI: 12 to 28• 80 out of 400 participants: 20%

95% CI: 16 to 24• 2000 out of 10000 participants: 20%

95% CI: 19.2 to 20.8

3131

3232

Quality assessment toolsQuality assessment tools

• Checklist : the components are evaluated separately and do not have numerical scores attached to them

• Scale: each item is scored numerically and an overall quality score is generated.

44 . .Apply the resultsApply the results

آیا تست یا درمان مورد نظر در بیماران مرکز طبابت من •قابل انجام است؟

آیا بیماران من متفاوت از افرادموجود در مطالعه است که •منجر به عدم کاربرد نتایج میشود؟

آیا روش دیگری در دسترس است؟•

آیا فواید بالقوه درمان بیش از زیانهای بالقوه آن •برای بیمار من است؟

بیمار من در این مورد چگونه فکر میکند؟•

3333

ThinkThink

اگر دانشجوییم وظیفه ما جستجوی علم و رعایت ادب و احترام استاد و ...

وظیفه ما این است که عمل به وظیفه کنیم

”Leonardo Davinchi“

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ReferencesReferences

• Paul glasziou, Chris Del Mar. Evidence-Based Practice workbook. University of Oxford; 2008

• Sackett DL, et al. Evidence Based Medicine: How to practice and teach EBM. Edinburge; 2000

• Glasziou P. Evidence based case report: Twenty year cough in a non-smoker. British Medical Journal 2006.

• http://www.cvidene-evidence-based medicine.com• http://www. Cochrane.org• Bero L, Rennie D. The Cochrane Collaboration. JAMA

2007 ;274:1935–8. • http://www.CONSORT-sratement.org/revisedstatement.htm.Vol.9 N

o.1, March 2007

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