Medical Education Development Series: Specialty Resources and Tools

for the Clinician

Sue McGuinness, PhD, MLS

Karen Heskett, MSI

Alice Witkowski, MLS

February 8, 2007

Learning Outcomes

• Understand basic principles of Evidence- Based Medicine (EBM)

• Be aware of EBM and Drug information Tools

• Practice Using EBM and Drug Information Tools

Evidence-Based Medicine• What Is It?

• Clinical Expertise + conscientious, judicious use of the best available evidence in making decisions about patient care

Expertise

Patient values

Evidence

Evidence-Based Medicine

• Why practice it? – Dispel “myths”– Deal with information overload– Aids decision making– Improves patient care

• Why teach it? – AAMC learning objectives– Improves critical thinking skills– Can apply to clerkships, residencies, rounds, PBL

courses, reading groups, journal clubs,

Barriers to practicing EBM

• Time

• Information Resources

• Cost

Analysis of questions asked by family doctors regarding patient care

Ely JW, et al. BMJ 1999;319:358-361

Physicians’ Information NeedsEly JW, Osheroff JA, Chambliss ML, Ebell MH, Rosenbaum MEJAMIA 12 (2): 217-224 MAR-APR 2005

Total QuestionsN=1,062

PursuedN= 585 (55%)

Not PursuedN= 477 (45%)

Answered, no difficultyN=238 (41%)

Answered with difficultyN=180 (31%)

Not AnsweredN=167 (28%)

Why? Limited time, Suspect lack of information, Need better resources.

How to practice EBM (The 5 A’s)

Assess- patient history, labs, meds, patient values

* Ask- build a focused searchable question

* Acquire- the best evidence you can find

Appraise- evaluate the evidence

Apply- to patient care

Categories of Clinical Questions

• Diagnosis – Test A or B to differentiate between positive an negative

• Therapy – treatment A or B to improve a condition or avoid an adverse event

• Prognosis – future course of condition or disease

• Etiology/harm- effects of agents on function, morbidity, mortality

Systematic Reviews & Meta-analyses of RCTs

Randomized Controlled Trials (RCTs)

Systematic Reviews of Observational Studies

Observational Studies

Retrospective (case-control)

Prospective (cohort)

Case Series

Case Reports

Hierarchy of Evidence

Best Evidence for Clinical Questions

Diagnosis and Therapy- randomized controlled trial

– Eligible patients

Prognosis and Etiology/Harm- observational studies

outcome

outcome

randomizationtreatment

placebo

Circumstances exposed

not exposed

outcome

No outcome

Eligible patients

Ask: Formulating the well- built clinical question

Pauline is a new patient who recently moved to the area to be closer to her son and his family. She is 67 years old and has a history of congestive heart failure brought on by several myocardial infarctions. She has been hospitalized twice within the last 6 months for worsening of heart failure. At the present time she remains in normal sinus rhythm. She is extremely diligent about taking her medications (enalapril, aspirin and simvastatin) and wants desperately to stay out of the hospital. You think she should also be taking digoxin but you are not certain if this will help keep her out of the hospital. You decide to research this question before her next visit. Introduction to Evidence-Based Medicine [online tutorial] Duke University Medical Center Library, UNC-\Chapel Hill health Sciences Library, 2004. http://www.hsl.unc.edu/services/tutorials/EBM/index.htm. Accessed 2/6/07

Ask: Build a focused query (PICO)

•P: terms describing the patient/problem•I: terms describing the intervention•C: list any alternative interventions•O: terms defining the outcome of interest

Do not need PICO for pre-filtered systematic reviews or meta-analyses

ASK: Focused query

• Patient / Problem

• Intervention

• Comparison

• Outcome

congestive heart failure, elderly

digoxin

none, placebo

primary: reduce need for

hospitalization

secondary: reduce mortality

The well-built clinical question

• In elderly patients with congestive heart failure, is digoxin effective in reducing the need for hospitalization?

• It is a therapy question:– The best evidence would be a a systematic

review or meta-analysis. If we couldn’t find one then look for randomized controlled trial (RCT).

Acquire:

Know the resources (ask a librarian!)

Find the best available evidence

Starting with PubMed

Acquire: Finding the best evidence in MedLine/PubMed:

Therapy Questions

• PICO using MeSH terms where available

• Limit to meta-analyses OR randomized controlled trials OR clinical trials

Therapy Question: Acquire

The effect of digoxin on mortality and morbidity in patients with heart failure. The Digitalis Investigation Group. New England Journal of Medicine February 20, 1997;

336(8):525-533.

Therapy Question: Appraise

Are the results valid?

What do the results mean? (are they important?)

Appraise: validity questions for therapy articles

Were patients randomized?

Was randomization concealed?

Were patients in experimental and control groups similar interms of prognostic factors?

Was follow up complete?

Answers: Article: This study methodology appears to be sound and the results are valid.

Appraise: Part 2- are the results important?

Outcome Placebo Digoxin

Hospitalization due to CHF

35% 27%

Appraise: Are the results important?Ways to quantify magnitude of treatment

effect Relative Risk: Risk of the outcome in experimental group compared to the risk in the control group. .

RR= outcome (exp) / outcome (con)

= 27/35= .77 = 77%

Relative Risk Reduction: The percent reduction ofrisk in the experimental group compared to the control group)

RRR = outcome (con) – outcome (exp) / outcome (con)= 23%

Appraise…Are the results important

Absolute Risk Reduction: The difference between outcome rates in experimental and control groups

ARR= outcome (con) – outcome (exp) Example: 35% - 27% = 8%

100%65% avoid the hospital either way

8% avoid the hospital by taking digoxin27% are hospitalized either way

Appraise: Ways to quantify effect

Number needed to treat (NNT): The number of patients that need to be treated to observe outcome in one patient.

Example ARR = 8%

Outcome (death) was avoided 8 times per 100 patients.

How many patients need to be treated in order to avoid one death? 8/100 = 1/NNT

NNT = 100% / ARR % = 100/8 = 13 patients need to be treated in order to avoid one hospitalization by using digoxin

RRR vs. ARR: Some papers report RRR only. Why is that a

problem?

% Mortality Treatment Control

RCT 1 10 15

RCT 2 40 60

RCT 3 60 90

Calculate RRR, ARR and NNT for the following three RCTs

RRR vs. ARR: RRR alone tells you nothing

RCT 1: RRR = .33 ARR = .05 NNT = 20

RCT 2: RRR = .33 ARR = .20 NNT = 5

RCT 3: RRR = .33 ARR = .30 NNT = 3

APPLY: Should we prescribe Digoxin for Pauline?

Diagnosis Questions

• Ask (PICO)

• Acquire (Systematic reviews, metaanalyses, RCTs)

• Appraise (Validity and Importance)– Validity questions differ for diagnosis– Data are different (sensitivity, specificity,

likelihood ratios)

Evidence-Based Medicine: How to practice and Teach EBM, Sackett DL, et al. NY: Churchill, 2000.

Diagnosis: Validity questions

• Key issues for Diagnostic Studies:– blinding – identified gold standard test– patient sample– each patient gets both tests

Diagnosis: Are the results important

• Sensitivity measures the proportion of patients with the disease who also test positive for the disease.

• Specificity measures the proportion of patients without the disease who also test negative for the disease.

Search Tip for Diagnosis

• Use the MeSH term “Sensitivity and Specificity”

• If that doesn’t work, use ONE of the terms in your search

Need a Break?

The Good News: We have Pre-Filtered Sources

• Cochrane Library/DARE• ACP Journal Club• NG Clearinghouse• Trip Database (FREE!)

Archie Cochrane 1909-1988

Demonstration: EBM resources

• Search “congestive heart failure” in Cochrane Library

• Search ACP journal Club

• Search TRIP database

Drug Information Questions

• Now that we’re giving Digoxin to Pauline, we need information on adverse effects, interactions with other drugs or foods, dosing information, and information for Pauline to read about her new medication.

Drug Information Resources

• Clinical Pharmacology

• Micromedex

• Exercises: work in groups, pick a question– Fred: Therapy– Amelia: Therapy– Myrtle: Diagnosis– Any questions you have had in your

practice

• ASK • ACQUIRE• Appraise, if you have time. Validity

questions are in your packet