Evidence Based Medicine

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Evidence Based Medicine
Teaching
At the Bedside

• Stephen R. Hayden, MD
• Department of Emergency Medicine
• UCSD Medical Center, San Diego

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The best teaching is taught by patients
themselves   Sir William Osler
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EBM at the Bedside

• At the bedside, use history and physical exam
  elements for teaching EBM
• Take an item of history or physical exam and
  think of it as a diagnostic test
• Presence or absence of a clinical finding changes
  the probability of disease

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EBM at the Bedside

• Opportunity to discuss many EBM concepts
• Test properties of clinical exam parameters
• Precision (kappa) of clinical examination
• Accuracy (likelihood ratios, PPV, NPV)
• Moving from pretest to post test probability
• Quantifies the utility of diagnostic tests

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Example

• How often do you see a case of chest pain in the
  emergency department?

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• How precise are clinical findings in chest pain
  patients?
• Interrater reliability (Kappa)

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Precision of Clinical Features
Clinical Feature Kappa
Chest pain radiates to L arm 0.89
Pain in substernal location 0.74
Pain described as pressure 0.57
Pain described as sharp 0.30
Pain with movement 0.27
Hickan DH, et al. J Chronic Dis. 19853891-100
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Precision of Physical Findings

• Physical signs of heart failure in MI

Clinical Feature Kappa
Dyspnea 0.62 - 0.75
Neck vein distension 0.31 0.51
Dependent edema 0.27 0.64
Third heart sound 0.14 0.37
Rales 0.12 0.31
Gadsboll N. European Heart J. 1989101017-1028
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• How accurate are clinical findings in chest pain
  patients?

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Accuracy of Clinical Features
Clinical Feature Positive LR (CI)
Radiation to left arm Radiation to right shoulder Radiation to both L and R arm 2.3 (1.7-3.1) 2.9 (1.4-6.0) 7.1 (3.6-14.2)
Third heart sound 3.2 (1.6-6.5)
Hypotension 3.1(1.8-5.2)
Diaphoresis 2.0 (1.9-2.2)
Nausea or vomiting 1.9 (1.7-2.3)
Past history of MI 1.5-3.0
Panju AA, et al. JAMA. 19982801256-1263
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Accuracy of Clinical Features
Clinical Feature Negative LR (CI)
Pleuritic chest pain 0.2 (0.2-0.3)
Chest pain sharp or stabbing 0.3 (0.2-0.5)
Positional chest pain 0.3 (0.2-0.4)
Chest pain reproduced by palpation 0.2 - 0.4
Panju AA, et al. JAMA. 19982801256-1263
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• Can this really be done in a busy ED?

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YES IT CAN!
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EBM at the Bedside

• Dont attempt to answer all possible questions
  for every patient
• Pick one clinical finding relevant to a
  individual patient
• Choose cases you see frequently in ED

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EBM at the Bedside

• Requires advance preparation
• Have Kappas, likelihood ratios with you on index
  cards, palm pilot, workstation
• Need rapid access to high quality evidence

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Medcalc3000.com
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http//pbrain.hypermart.net/medrules.html
(Freeware)
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BestBets.org
Analgesia and Abdominal Pain
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http//nhscrd.york.ac.uk/darehp.htm
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ACP Journal Club
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• How do you find articles relating to the
  precision and accuracy of the HP?

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Search Tips

• Add specific terms to search strategy
• Physical examination
• Medical history taking
• Sensitivity or specificity
• Clinical assessment
• Observer variation
• Interrater reliability

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MI Reference

• Panju AA, et al. Is this patient having a
  myocardial infarction? JAMA. 19982801256-1263

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Summary

• Reviewed how to take EBM to the bedside
• Identifying elements of the HP as tests
• Describing precision and accuracy of HP
• Preparing in advance / bedside tools
• Rapid access to pre-appraised resources

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• I desire no other epitaph than the statement
  that I taught medical students in the wards, as I
  regard this by far the most useful and important
  work I have been called upon to do.

Sir William Osler Farewell Address, 1905