The document provides an overview of critical appraisal of medical research. It discusses study designs such as randomized controlled trials, observational studies, systematic reviews and meta-analyses. It also covers topics like developing PICO(T) questions to frame clinical questions, different types of study questions, evaluating studies using the FRISBE mnemonic, calculating measures of clinical importance, and resources for evidence-based practice.

1. Critical Appraisal
of Medical Research
Susan Fowler, MLIS
314-362-8092
fowler@wustl.edu
Photo: http://www.pantherkut.com/2009/05/27/cat-thoughts/

2. Agenda
• Study Design
• PICO(T)
• Types of Questions
• FRISBE
• Clinical Importance
• 3 Therapy
Examples
• Resources
Photo: http://catscientists.tumblr.com/post/19458666129
Susan Fowler, MLIS Washington University in St. Louis

3. Photo: http://kuln.es/c5cwg
Susan Fowler, MLIS Washington University in St. Louis

4. Basic Study Designs
Experimental Observational
• Investigator • Investigator observes
manipulates a variable outcome of naturally
and examines effect on occurring difference in a
an outcome variable
• Designs • Designs
– randomized controlled – Cohort study
trial – Case control study
– Controlled clinical trial – Case series study
Systematic Review Workshop ©HSLS – University of Pittsburgh

5. Study Designs Defined
meta-analysis: a quantitative approach in which individual study findings addressing a
common problem are statistically integrated and analyzed to determine the
effectiveness of interventions.
systematic review: a process by which a body of literature is reviewed and assessed
using systematic methods which are intended to reduce bias in the review process
and improve understandability. A controlled clinical trial in which the study groups
are created through randomization.
randomized controlled trial: an experiment in which investigators randomly allocate
participants into (eg treatment and control) groups to receive or not to receive one
or more interventions that are being compared.
controlled clinical trial: any study which compares two groups by virtue of different
therapies or exposures.
cohort study: an observational study in which a cohort is followed over time.
case-control studies: retrospective research design that compares individuals with a
specific condition to those without it.
case report: a detailed report of the symptoms, signs, diagnosis, treatment, and
follow-up of an individual patient.
case series: a report on a series of patients with an outcome or condition of interest.
Susan Fowler, MLIS Washington University in St. Louis
2012

6. PICO (T)
• Patient or problem - How would I describe a group of
patients similar to mine?
• Intervention - Which main intervention, prognostic
factor, or exposure am I considering?
• Comparison (if appropriate)- What is the main
alternative to compare with the intervention?
• Outcome - What can I hope to accomplish, measure,
improve or affect?
• Type of Study – Based on my question, what type of
study will provide the best answer?
Susan Fowler, MLIS Washington University in St. Louis
2012

7. Types of Questions
Type of Question Ideal Type of Study
Therapy RCT
Prevention RCT > Cohort > Case Control
Diagnosis Prospective, blind controlled
comparison to gold standard
Prognosis Cohort > Case Control > Case
Series/Case Report
Etiology/Harm RCT > Cohort > Case Control
Susan Fowler, MLIS Washington University in St. Louis
2012

8. *FRISBE
•Follow Up
•Randomization
•Intention to Treat
•Similar Baseline
•Blinding
•Equal Treatment
*Mnemonic tool created by Connie Schardt, AHIP
Susan Fowler, MLIS Washington University in St. Louis
2012

9. Follow Up – Were all patients who entered the trial
properly accounted for and attributed at its
conclusion?
Randomization - Was the allocation (assignment) of
patients to treatment randomized?
Was the allocation concealed?
Intention-to-Treat Analysis - Were patients analyzed
in the groups to which they were
randomized? Were all randomized patient
data analyzed?
Similar Baseline Characteristics of Patients - Were
groups similar at the start of the trial?
Blinding - Were patients, health workers, and study
personnel "blind" to treatment?
Equal Treatment - Aside from the experimental
intervention, were the groups
treated equally?
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Susan Fowler, MLIS Washington University in St. Louis

10. Clinical
Importance

11. EER (Experimental Event Rate): The proportion of patients in the experimental
treatment group who are observed to experience the outcome of interest.
CER (Control Event Rate): The proportion of patients in the control group
observed to experience the outcome of interest.
ARR (Absolute Risk Reduction): The absolute arithmetic difference in rates of bad
outcomes between experimental and control participants in a trial. (Also referred to
as risk difference).
RRR (Relative Risk Reduction): The proportional reduction in rates of bad
outcomes between experimental and control participants in a trial.
NNT (Number Needed to Treat): The number of patients who need to be treated
with the specified intervention to prevent one bad outcome or to produce one good
outcome over the period of time specified in the study.
Susan Fowler, MLIS Washington University in St. Louis
2012

12. Outcome Outcome
Present Absent
Treated a= b= EER
Exposed a
a+b
Control/not c= d= CER
exposed c
c+d
RRR ARR NNT
CER EER (CER-EER) CER-EER 1
CER ARR
Susan Fowler, MLIS Washington University in St. Louis
2012

14. Susan Fowler, MLIS Washington University in St. Louis
2012

15. Library Resources
Evidence at Becker (How To):
http://beckerguides.wustl.edu/ebm
Duke University Evidence-Based
Practice:
http://guides.mclibrary.duke.edu/eb
m
Centre for Evidence Based
Medicine:
http://www.cebm.net/index.aspx?
o=1023
Susan Fowler, MLIS
fowler@wustl.edu
314-362-8092
Clip Art from http://www.wpclipart.com/
Susan Fowler, MLIS Washington University in St. Louis

16. Q
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Photo by Juniors Bildarchiv
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Susan Fowler, MLIS Washington University in St. Louis
2012