DEPARTMENT OF FAMILY AND COMMUNITY MEDICINE

UP-PHILIPPINE GENERAL HOSPITAL

INTRODUCTION TO

EVIDENCE-BASED MEDICINE

OBJECTIVES1. To define Evidence Based-Medicine Family

and Community Practice (EBMFCP)2. To discuss the uses (importance) of

EBMFCP3. To discuss the foundations of a clinical

dilemma (clinical question) based on a patient’s case scenario

4. To discuss the different strategies in searching for answers

5. To discuss the steps regarding the critical appraisal of a journal

IntroductionMedicine is not an exact science. Medicine is a dynamic field of knowledge.

Problems arise

New information regarding therapeutics and diagnostics

Affect patient management

Quality of care changes

In our day to day encounter with patients we often find ourselves facing a dilemma or questions in regard to:

Therapeutics

Diagnostics

Differential diagnoses

Prognosis

Harm

Diagnosis How to select and interpret the appropriate diagnostic tests

Therapy How to select treatments to offer patients that do more good than harm and that are worth the efforts and costs of using them

Prognosis How to estimate the patient’s likely clinical course over time and anticipate likely complications of disease

Harm/Etiology How to identify causes for the disease (including iatrogenic forms)

Patients usually serve as the starting point

Good questions are the backbone of EBM

Searching for the right answers is usually the hardest step.

RESOLUTION OF THE CLINICAL DILEMMA

Looking for answers

The usual thing…………When asked or in doubt, > we get it from books and journals > ask other: friends, colleagues, mentors,

subspecialty experts

However,

OUR INFORMATION NEEDS ARE NOT MET!!!

our textbooks are out of date by the day they are published

our journals are disorganized and inaccessible to us

our colleagues may not have the answers that we seek

Evidence Based Medicine

New Paradigm

Search for the CURRENT BEST EVIDENCEAppraise Decide and ApplyEvaluate

WHAT IS EBM?

“The conscientious, explicit and judicious use of current best evidence in making decisions about the care of the individual patient. It

means integrating individual clinical expertise with the best available external clinical

evidence from systematic research."Dr. David Sackett, 1996

EBM is a systematic approach ACQUISITION APPRAISAL APPLICATION of Research

to guide decisions in health care

ADVANTAGES OF EBFCP

TO DOCTORS:

Lifelong learning Continuing professional development Keeping up to date

Better quality of careCost-effective careBetter outcomes

TO PATIENTS:

TO THE HEALTH CARE SYSTEM:

Better utilization of healthcare resources

The Evidence-Based Family and Community Practitioner

Clinical

ExperiencePatient Values

Evidence

DECISION

Ask

Acquire

Appraise

Apply

Act & Assess

Patient dilemma

Principles of evidence-based

practice

Evidence alone does not decide – combine with otherknowledge and values

Hierarchy of evidence

Process of EBP

Steps in the EBM Process

CLINICAL SCENARIOMaria, 50/FHistory of CHF 2o to several Myocardial

InfarctionsHospitalized 2x w/n the last 6 months due to

worsening of heart failure

Normal sinus rhythm presentlyEnalapril, aspirin and simvastatinWants desperately to stay out of the hospitalDigoxin (?)

CLINICAL SCENARIO

You think she should also be taking digoxin but you arent certain if this will help keep her out of the hospital.

You decide to research this question before her next visit.

Background Questions:

Ask for general knowledge about a disease or disease process, tests, treatments, etc. 2 components:

a. root* + verb “What causes….” b. condition …. SARS?”

* Who, What, Where, When, How, Why

Usually asked because of the need for basic information.Answering the background question. textbooks,

handbooks and databases

Foreground Question:

About patient care decisions and actions

4 (or 3) components: a. Patient, problem or population b. intervention, exposure, or manuever c. comparison (if relevant) d. clinical outcomes (including time horizon)

e.g: in young children with acute otitis media, is short-term antibiotic therapy as effective as long term antibiotic therapy?

Formulating a Focused Question

Population (P) – general characteristics of the group of subjects in question

Intervention(I) – drug or treatment, diagnostic test, risk factor or anything that is being tested

Outcome (O) – endpoint against which a certain intervention is measured

Methodology (M) – study design

Translate dilemmas into questionsKeep the questions simple, relevant, and manageableComplex questions: FRUSTRATION!!

Patient/problem Congestive heart failure, elderly

Intervention Digoxin

Comparison, if any None, placebo

Outcome Primary:reduce need for hospitalizationSecondary: reduce mortality

The question:

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

THE SEARCH

Identify key termsUse the boolean principle (Venn diagram) in

combining termsUse OR to broaden searchUse AND to narrow down searchUse of “Quotation Marks”Use of the MeSH Use of limitsUse of truncations

The Key Terms

Population – elderly hypertensives with CHFIntervention – digoxinOutcome – rate of hospitalizationMethodology – RCT

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

The Boolean Principle

Congestive Heart

FailureDigoxin

Hospitalization

OR to broaden search

AND to narrow down search

The Evidence Pyramid

Meta-AnalysisSystematic Review

Randomized Controlled TrialCohort Studies

Case-Control StudiesCase Series/Case Report

Animal Research/Laboratory Studies

Type of Question

Suggested Best Type of Study

Therapy RCT > Cohort > Case-Control > Case Series

Diagnostic Prospective, blind comparison to a gold standard

Etiology/Harm RCT > Cohort > Case-Control > Case Series

Prognosis Cohort > Case Control > Case Series

WHAT TO ACCESS?

www.nlm.nih.govwww.nejm.com www.bmj.com www.freemedicaljournals.com www.medscape.com www.pubmed.com

What do we do with our output?

When you have the article, appraise it using the Evidence-Based Family and Community Practice and Quality Improvement in Health Care Manual (FMRG, 2003)

Weigh the evidence afforded by the article

EVIDENCE-BASED FAMILY AND COMMUNITY PRACTICE

I. Is it relevant?II. Is it valid?III. What are the results?IV. Is it applicable to my patient?

JOURNAL REPORT FORMAT

Case ScenarioResearch QuestionSearchTitleSourceAuthorsAppraisal

CRITICAL APPRAISAL OF AN ARTICLE ON

THERAPEUTICS

CRITICAL APPRAISAL OF AN ARTICLE ON THERAPEUTICS

I. Is it relevant?Is the objective of the study similar to your

clinical dilemma? population of the study intervention and comparative interventions outcome of the study

2. Was follow-up complete?

Methodology and Result Section

Look at the number of patients enrolled at the outset and compare this with the number of patients reported in the results table

A drop-out rate of 20% or more is usually declared substantial, if otherwise, check whether an intention to treat analysis was done.

What is the drop-out rate?

Secondary Guides:

1. Was the study blinded?

What is the definition and importance of blinding?

Look at the methodology and results section.

Single Blinding?

Double Blinding?

Triple Blinding?

2. Were the outcome measurements clearly described and determined in the same way between interventions?

whether the outcome measures are those which you and your patient are interested in

Surrogate outcome?Clinical outcomes?

Overall, is the study valid?

III. What are the results?

A. How large was the treatment effect? Risk in Control (Rc):

Risk in Treatment (Rt):

No. pxs who did not get well in the control

Total no. of pxs in the control group

No. who did not get well in the txt group

Total no. pxs in the treatment group

Absolute Risk Reduction (ARR) = Rc - Rt

Relative Risk (RR) = Rt/RcRR of 1 : No difference between Treatment and ControlRR of >1: Treatment is more harmfulRR of <1: Treatment is more effective

Relative Risk Reduction (RRR) = 1 – RR

B. Are the results reliable?

What is the confidence interval?What is the p-value?

IV. Are the Results Applicable to My Patient?Are the medical, social and economic resources needed to administer the treatment available in your setting?

In your perception, were the treatment and its outcome as measured in the article preferred by the patient and his family?

Do you think that the patient, family, and/or community will be willing to accept and pay for the treatment in question?

Number Needed to Treat = 1/ARRCost-Effectiveness Formula: NNT x price/unit x dose x duration

RESOLUTION OF THE THERAPEUTIC DILEMMA

CRITICAL APPRAISAL OF AN ARTICLE ON

DIAGNOSTICS

The Decision Analysis- Establish Diagnostic and therapeutic thresholds

Diagnostic Threshold (DT): arbitrary point at which you rule out the diseaseTherapeutic Threshold (TT): arbitrary point at which you decide to treat

- Determine other parametersPre-test Probability: probability that the patient has the diseasePost-test Probability: probability that the patient has the disease after doing the diagnostic exam

DT TT.50 1

30 80.50 1

30 80.50 1

30 50.50 1

30 50.50 1

Search

Appraise

DETERMINE THE POST-TEST PROBABILITY

CRITICAL APPRAISAL OF AN ARTICLE ON DIAGNOSTICSI. Is it relevant?Is the objective of the study similar to your clinical

dilemma? - population of the study - intervention and comparative interventions - outcome of the study

Primary Validity Guides:

II. Is it valid?

Was there a comparison with a reference standard? Whether the reference standard was done regardless

of the results of the diagnostic test Meaning of reference standard? Precision? Accuracy?

CRITICAL APPRAISAL OF AN ARTICLE ON DIAGNOSTICS

II. Is it valid?

2. Did the patient sample include an appropriate spectrum of patients on whom the test will be used?

Representativeness includes subjects with the whole spectrum of the disease.

-Exclusion and Inclusion Criteria

The accuracy of a diagnostic test among patients with low risk for the disease is different from patients with high risk for the disease.

2. 3. Was the reading or interpretation of the diagnostic test and reference standard done independently?

Presence of blinding

Evaluates the performance of the diagnostic test independently

Avoids bias

2. 4. Was the diagnostic test and reference standard described in detail to permit replication?

Clear procedures including preparation of subjectsDiet, Drugs to avoid, precautions Step by step descriptions

Be able to duplicate the test and get the same outcome.

Look at the “results and methodology” section

III. What are the results?

What are the likelihood ratios for the different testresults?

- Sensitivity and Specificity- Likelihood Ratios- Pre and Post Test Probabilities

Recall: Sensitivity and Specificity

Present Absent

Positive TP FP

Negative FN TN

Disease

Test

Sensitivity: probability/likelihood that the diseased patient will test positive

Specificity: probability/likelihood that those without the disease will test negative

TP/TP+FN

TN/TN+FP

Presumptions:

Pre-test probabilities will have a profound effect on the post-test probabilityDiagnostic tests provide more information when the diagnosis is truly uncertain than when the diagnosis is either unlikely or truly certain.

- if results of the test could shift the probability of the disease across the treatment threshold

- Using likelihood ratios- Using likelihood ratios and a nomogram

Post-test Probability

Estimates make quick assessment of the usefulness of a contemplated diagnostic test.

Likelihood ratios- Uses sensitivity and specificity values- utilizes the 2 x 2 contingency table

Probability of result in diseased personsProbability of result in non-diseased persons

Every test has two likelihood ratios: LR (+) and LR (-)LR (+) :Probability that test is + among diseased persons

Probability that test is + among non-diseased persons

Sensitivity

1- Specificity

LR (-) :

Probability that test is - among diseased personsProbability that test is - among non-diseased persons

1-Sensitivity Specificity

Using likelihood ratios and a nomogram

Establish pre-test probabilities

Calculate the LR

Plot

30 50.50 1

Search

Appraise

DETERMINE THE POST-TEST PROBABILITY

The Decision Making Line

DT TT

TREAT!!!Don’t start treatment!

IV. Can the Results Help Me in Caring for My Patient?

1. Will the reproducibility of the test result and the interpretation be satisfactory in my setting?

2. Are the results applicable to my patient?

3. Will the result change my management?

RESOLUTION OF THE DIAGNOSTIC DILEMMA

Sources:

http://www.hsl.unc.edu/Services/Tutorials/EBM/welcome.htm EBM ’08 edition UP-PGH DFCM http://www.cebm.net/index.aspx?o=1001 http://www.med.yale.edu/library/nursing/education/

clinquest.html

THANK YoU! The doctor of the future will give no medicine, but will interest her or his patients in the care of the human frame, in a proper diet, and in the cause and prevention of disease.

Thomas A. EdisonUS inventor (1847 - 1931)