Levels of Evidence

1
Levels of Evidence

• OT 653
• 9/24/03

2
What is evidence?Support for clinical practice,
theory, assessments, and clinical research
evolved from systematic study
3
(No Transcript)
4
Randomized Controlled Trials

• Control group
• Manipulate a variable
• Random assignment
• Double-blinded (persons administering the
  treatment and evaluating the outcomes are both
  blinded to who receives what intervention)

5
Other Kinds of Experimental Designs

• Studies where groups are small (under 30)
• Lack of blinding of researcher or data
  collector or data analyzer

6
Cohort Studies

• Follows one or more groups (cohorts)
• Follows the group over a defined time
• prospectively
• Often used to follow a group of individuals
  over a period of time to see if a certain
  condition develops.
• Helps to delineate risk factors for conditions
• Not randomized

7
Case-Control Studies

• Similar to cohort studies BUT
• Are retrospective
• Subjects in two groups are matched -
  participants with a condition in one group and
  participants without in the second group or
  cohort
• Identify risk factors, make predictions
• Do not identify causation

8
Quasi-experimental Studies

• Studies without a control group
• Studies without a control group and without
  random assignment
• Studies where either pre and post intervention
  measures are collected, or sometimes just post
  intervention measures

9
Cross-sectional studies

• Data collected on a group at one point in time
• The group studied may be stratified
• Conclusions are drawn about the trait studied

10
So how are all these kinds of research worked
into an evidence-based review??
11
Evaluating the Evidence

• Doing a literature review
• Analyzing kinds of evidence you
• find
• Deciding which articles to include in
• your review
• Ranking kinds of research

12
Ranking articles for an evidence-based review is
carried out using levels of evidence hierarchies.
13
Such hierarchies are a way to rank kinds of
research studies in a systematic and consistent
manner.
14
Levels of Evidence

• There are a number of levels or typologies of
  evidence
• Groups like the Cochrane Collection or the
  PEDRO group out of Australia use very rigorous
  levels

15
http//www.pedro.fhs.usyd.edu.au/Links/links.htm
16
In the Future

• For clinicians, use of high levels of evidence
  often results in finding very limited studies
• Fields like physical and occupational
• therapy (even medicine) will have more
• RCTs available in the future as evidence
• Use of more rigorous levels of evidence
• will be mandatory
• In the meantime, practicing clinicians
• need to use levels commiserate with
• existing evidence

17
Laws Levels of Evidence

• Level I - RCTs or meta-analysis of RCTs
• Level II - Small RCTs
• Level III - Nonrandomized, controlled or cohort
  studies case series case-controlled or
  cross-sectional studies
• Level IV - opinions of respected authorities or
  expert committees consensus statements
• Level V - Opinions of individuals who have
  written guidelines based on experience,
  literature reviews, and discussion with peers.

18
Systematic Reviews/Meta-Analyses

• Systematic Reviews - comprehensive reviews of the
  literature that provide an overview of validity
  of research methods and results for a particular
  topic
• Meta-Analyses - a systematic review in which
  studies are summarized statistically

19
Problem - Laws levels of evidence is very
rigorous and may exclude much of the research
that exists in occupational therapy
20
Holms Levels of Evidence

• Level I - Systematic reviews, meta-analytic
  studies
• Level II - Randomized controlled trials
• Level III - Trials without randomization
• Level IV - Nonexperimental studies from more than
  one center
• Level V - Opinions of respected authorities based
  on clinical evidence, descriptive studies or
  reports of expert committees
• (Holm, 2000, p.581)

21
Level III

• Studies included in Level III are studies
  without randomization, cohort studies, or
  case-control studies. (FOR THE PURPOSE OF THIS
  CLASS, PUT SINGLE SUBJECT DESIGNS IN LEVEL III).

22
Level IV

• To be classified as Level IV, studies must
  include data from more than one site, i.e.
  multiple classrooms, several clinical or practice
  sites, more than one university setting.

23
Level V criteria

• Qualitative studies
• Descriptive studies from individual centers
• White papers, The Issue is, published
  standards of care

24
For your group reviews...

• A table citing articles included in your paper
  grouped by levels of evidence
• You do NOT have to do a critique using the form
  from last semester on meta-analyses or systematic
  reviews done by groups such as the Cochrane
  Collection
• You MUST have a critique on all other articles
  except expert opinion papers

25

http//www.uab.edu/shrpot/Laura20Vogtle/OT667/Sch
ool20Based.pdf
26
http//www.uab.edu/shrpot/Laura20Vogtle/OT667/Cas
e20Study20Article20Critique.pdf