Evidence-Based Medicine

Applying the Concepts to Pediatric Nutrition Practice and

Consultation

What evidence-based medicine is:

Evidence-based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients.

Sacket et al. BMJ 1996

What evidence-based medicine is:

The practice of EBM requires the integration of

individual clinical expertise

with the best available external clinical evidence

from systematic research.

Evidence Based Medicine is Not:

Cook-book medicine Cost cutting medicine Restricted to randomized trials and

meta-analysis

“If no randomized trials have been carried out for our patient’s predicament, we follow the trail to the next best external evidence and go from there.”

Sacket et al. BMJ 1996

Why EBM?

Clinicians need information If asked:

» we need it twice a week,» we get it from our text books & journals.

Clinicians really need information!

If shadowed: they need it up to 60 times per week but

only 30% of it and that comes from passers-by

» “my textbooks are out of date”» “my journals too disorganized”

Medical textbooks are out-of-date

Fail to recommend Rx up to ten years after it’s been shown to be efficacious.

Continue to recommend therapy up to ten years after it’s been shown to be useless.

Three solutions

Clinical performance can keep up to date:1 by learning how to practice evidence-

based medicine ourselves.2 by seeking and applying evidence-based

medical summaries generated by others.3 by accepting evidence-based practice

protocols developed by our colleagues.

Process of EBM

Define the question Plan and carry out search of the

literature Critically appraise the literature Apply the results to your practice Evaluate your performance

Step 1: Define Question

P - Patient and disease

I - Intervention

C - Comparative intervention (optional)

O - Outcome

Step 2: Search for Evidence

Translate PICO Question into a searchable question

Establish a search strategy» key concepts» boolean operators» synonyms» prioritize» limit

Step 2: Search for Evidence

Sources Tools

Reviews Medline

Meta-analysis Medline, Cochrane

Practice Guidelines Nat’l Clearinghouse

Sytematic Reviews Cochrane, EBMjournals

Step 3: Critically Appraise

http://healthlinks.washington.edu/help/evidence/

Step 4: Apply Results

Within context of individual patient preferences, values and rights

Evidence, Values, and Resources

Values

Evidence Resources

The Strength of the Evidence Depends on Study Design

Randomized Controlled Clinical Trial

Involves one or more test treatments and a control treatment

Specified outcome measures for evaluating the intervention

Bias free method for assigning treatment

Randomized Controlled Clinical Trial

Advantages Disadvantages

Unbiaseddistribution ofconfounders

Expensive

Blinding more likely Volunteer bias

Randomizationfacilitates analysis

Ethically problematicat times

Confounding Variable

“An extrinsic factor that is associated with the predictor variable and a cause of the outcome variable.”

Hulley and Cummings, Designing Clinical Research

Cohort Study

Identification of two groups» one received exposure of interest» one did not receive exposure

Follow cohort through time to observe the outcome of interest

Cohort StudyAdvantages Disadvantages

Ethically safe Controls may be hard to ID

Subjects can be matched Exposure may be linked to aconfounder

Can established timing of events Blinding is difficult

Eligibility and outcomeassessment standardized

Ramdomization not present

Easier and cheaper than RCT Large sample or long FU may beneeded

Case-control Study

Identify patients who have the outcome of interest (cases)

Identify controls without the same outcome

Look back to see if they had the exposure of interest

Case-control Study

Advantages Disadvantages

Quick and cheap Reliance on recall to determineexposure

Good for raredisorders or longlag

Confounders

Selection of control groups isdifficult

Fewer subjects thanin cross-sectional

Potential selection bias

Cross Sectional Study

Observation of a defined population at a single point in time or time interval

Exposures and outcomes determined at same time

Cross Sectional Study

Advantages Disadvantages

Cheap and simple Can’t establish causality

Ethically safe Recall bias

Confounders may beunequally distributed

Group sizes may beunequal

Study Design

Cross Sectional - association Case Control: exposure outcome Cohort: exposure outcome Randomized controlled trial

Meta-analysis

Quantitative method of combining the results of independent studies

synthesizing summaries and conclusions

The Five Strengths of Evidence

Strong Evidence from at least one systematic review of multiple well-designed RCT

Strong evidence of at least one well designed RCT of appropriate size

Evidence from well designed trials without randomization, single group pre-post, cohort, time series or matched case control

Evidence from well designed non-experimental studies from more than one research group

Opinions of respected authorities based on clinical evidence, descriptive studies or reports of expert committees

Barriers and BridgesHaynes and Haines, BMJ 1998

“Preliminary studies far outnumber definitive ones, and all compete in the medical literature for the attention of readers.”

“Models for critically appraising evidence have been developed, but applying these is time consuming.”

EBM Review: Example

A Systematic review of nonpharmacological and nonsurgical therapies for gastroesphageal reflux in infants. Carroll et al. Arch Ped Adol Med. Feb 2002;156:109.

Step 1: Define Question

P - Patient and disease

I - Intervention

C - Comparative intervention (optional)

O - Outcome

P: Patient and Disease

Patient = infants

Disease = GERD

I. Intervention (s)Placement upright in an infant seat

Elevating the Head

Pacifier Use

Thickening food with rice flour

Thickening food with carob bean gum preparation

Changing composition of Formula

Changing caloric density or osmolality

C. Comparative Intervention

Carob bean gum compared to rice flour

O. Outcome“Effect on reflux”

Included:» reflux duration (pH probe)» reflux frequency (pH probe)» clinical score» emesis

Search for Evidence

Medline, EMBASE, Cochrane, others search terms: gastroesophageal reflux

disease and infants (>2500 articles) excluded: non-clinical trials, drug or

surgical therapy included, study included infants with compound medical problems/prematurity

10 RCT met selection criteria

Critically appraise the literature

Study one: 52 infants randomly received apple juice or apple juice with rice flour, placed in one of 4 positions, monitored with pH probe for 2 hours. No differences except that more reflux with 30o elevation and rice flour.

Example:Thickening with rice flour/cereal - 2 studies

Study 2. 20 infants with paired feeding crossover design given formula with and without rice cereal thickening and monitored via technetium scintigraphy. No differences on reflux, but decrease in frank emesis.

Apply results

“Many conservative measures commonly used to treat GERD in infants have no proven efficacy.”

Medline

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed

Under “Limits” can select:» Review» Meta-analysis» Practice Guidelines» Randomized Controlled trial

Cochran Database of Systematic Reviews

http://www.cochranelibrary.com/enter Can search and review abstracts for free

Full text requires subscription

National Guidelines Clearing House

http://www.guideline.gov/

Haynes & Haines, BMJ 1998