Transcript EBM - Chapter 4 - Prognosis

Evidence-Based Medicine
How to Practice and Teach EBM
Chapter 5: Therapy, Part 2
Thomas F. Byars
Vanderbilt Sports Medicine
Qualitative literature
Qualitative research may provide us with some
guidance in deciding whether we can apply the
findings from quantitative studies to our
patients
It allows us to interpret clinical phenomena
through an emphasis on understanding the
experiences and values of our patients
VSM
Is the evidence valid, important, and
applicable?
1. Was the selection of participants explicit and
appropriate?
• Appropriate in the sense of representative of the
population we are interested in and who are relevant to
the study question
2. Were the methods used for data collection and analysis
explicit and appropriate?
• Direct observation, interviews, focus groups, etc;
blinding may limit investigators interpretation of data
VSM
Is the evidence valid, important, and
applicable?
3. Are the valid results important, are they impressive?
• Sufficient detail for us to obtain a clear picture of the
phenomena described
4. Are these valid important results applicable to my
patient?
• Do we think these same phenomena apply to our
patient?
VSM
Systematic Reviews
Summary of medical literature that uses
explicit methods to systematically search,
critically appraise, and synthesize the world
literature on a specific issue
Goal is to minimize both bias and random
error
VSM
Is the evidence from this SR valid?
1. Is this a SR of randomized trials?
By combining all relevant randomized trials, they further
reduce both bias and random error, providing the highest level
of evidence available
2. Does it describe a comprehensive and detailed search for
relevant trials?
3. Were the individual studies assessed for validity?
Methods of randomization, blinding, similar groups, sufficient
f/u, etc
4. Were individual patient data (or aggregate data) used for the
analysis?
Individual patient data allows you to test promising subgroups
from one trial in an identical subgroup from others
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Is the evidence from this SR important?
1. Are the results consistent across studies?
We’d be more likely to believe the results if every trial
shows a treatment effect that is at least going in the
same direction; ideally, investigators should test their
results to see whether any lack of consistency was not
from chance alone
2. What is the magnitude of the treatment effect?
Clinical usefulness of NNT (NNH) and conversion of
ORs and RRs
VSM
Is this valid, important evidence from this SR
applicable to my patient?
1. Is our patient so different from those in the study that
its results cannot apply?
2. Is the treatment feasible in our setting?
3. What are our patient’s potential benefits and harms
from the therapy?
4. What are our patient’s values and expectations for both
the outcome we are trying to prevent and the adverse
effects we may cause?
VSM
Clinical Decision Analyses
• Applies explicit, quantitative methods to compare the likely
consequences of pursuing different treatment strategies, and
integrates the risks of benefit and harm associated with the
various treatment options with values associated with the
treatments and with potential outcomes
• Starts with a diagram called a decision tree, illustrating the
target disorder, alternative treatment strategies and their
possible outcomes
• The “winning” strategy, and preferred course of action, is the
one that leads the highest utility (measure of a person’s
preference for a health state; usually decimal from 0-1 and
typically 1= perfect health, 0=death)
VSM
Is this evidence from a CDA valid?
1. Were all therapeutic alternatives (including no
treatment) and outcomes included?
• Should include all treatment strategies and full range of
outcomes (good and bad)
2. Are the probabilities of the outcomes valid and credible?
• There may be some uncertainty around a probability
estimate, but authors should specify a range
3. Are the utilities of the outcomes valid and credible?
• Ideally, utilities are measured in patients using valid,
standardized methods
VSM
Is this valid evidence from a CDA important?
1. Did one course of action lead to clinically important
gains?
2. Was the same course of action preferred despite
clinically sensible changes in probabilities and utilities?
Is this valid and important evidence from a CDA
applicable to our patient?
1. Do the probabilities in this CDA apply to our patient?
2. Can our patient state his/her utilities in a stable, usable
form?
• Generate utilities for our pt and determine if they fall w/in the
range tested in the CDA
VSM
Economic analyses
Compare the costs and consequences of different management
decisions; consider “opportunity costs”
Is this evidence from a economic analysis valid?
1. Are all well-defined courses of action compared?
2. Does it provide a specified view from which the costs and
consequences are being viewed?
• Patient, hospital, local gov’t
3. Does it cite comprehensive evidence on the efficacy of
alternatives?
4. Does it identify all the costs and consequences we think it should
and select credible and accurate measures of them?
• Direct and indirect costs
5. Was the type of analysis appropriate for the question posed?
• cost minimization analysis, cost-effectiveness analysis, costbenefit analysis, etc.
VSM
Is this valid evidence from an economic analysis
important?
1. Are the resulting costs, or cost per unit of health gained,
clinically important?
• Does the intervention provide a benefit at an acceptable cost
2. Did the results of this economic analysis change with
sensible changes to costs and effectiveness?
Is this valid and important evidence from an
economic analysis applicable to our patient?
1. Do the costs in the economic analysis apply in our
setting?
2. Are the treatments likely to be effective in our setting?
VSM
Clinical Practice Guidelines
Systematically developed statements to help clinicians and
patients with decisions about appropriate health care for
specific clinical circumstances
Before considering using one, think of it as having two distinct
components:
1. Evidence summary (“avg effect of this intervention on the
typical pt who accepts it”) and
2. Detailed instructions for applying that evidence to our
patient
Valid guidelines create their evidence components from
systematic reviews of all the relevant worldwide literature
VSM
Guides for deciding whether a guideline is valid
and applicable to my pt/practice/hospital
1.
2.
3.
Did it’s developers carry out a comprehensive, reproducible
literature review within the past 12 months?
Is each of it’s recommendations both tagged by the level of
evidence upon which it is based and linked to a specific
citation?
Applicability of a guideline depends on the extent to which
it is in harmony or conflict with four local factors: Killer B’s
1.
2.
3.
4.
Is Burden of illness too low to warrant implementation?
Are the Beliefs of individual pts or communities about the value of
the interventions or their consequences incompatible with the
guideline?
Would the opportunity cost of implementing this guideline constitute
a bad Bargain in the use of our energy or our community’s
resources?
Are the Barriers (geographic, traditional, behavioral, etc.) so high
that it is not worth trying to overcome them?
VSM
N-of-1 Trials
1.
2.
3.
4.
5.
Important points/pitfalls associated with a “trial of therapy”:
Some target disorders are self limited
Both extreme lab values and clinical signs, if left untreated,
often return to normal
A placebo can lead to substantial improvement in symptoms
Both our own and our pts expectations about the
success/failure of a treatment can bias conclusions about
whether a treatment actually works
Polite pts may exaggerate the effects of therapy
N of 1 trial is employed when there is significant doubt
about whether a treatment might be helpful in a particular pt,
and is most successful when directed toward the control of
symptoms or relapses from a chronic disease
VSM