Critical Appraissal (Diagnostic, Therapy, Prognosis,
Etiology)ValidityPrecisionAplicability
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Implementation of the best evidenceobtained from clinical
research to clinical practiceWhat is EBM?
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What is in the real world?Haynes (An Intern Med 1986; 309 :105)
; 800 research articles in 4 famous journals valid only 19%
Reid (JAMA 1995; 274: 651); 1300 research articles on accuracy
of diagnostic tools from urine dipstick to MRI and CT scan valid
only 6%
Cohrane Collaboration (1996): out of 16,000 studies on mild
hypertension valid only 22
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What is in the real world?The case of gastric freezing machineIn
the 70s, 2500 gastric freezing machines for treatment of gastric
bleeding were sold Until a randomized trial showed this machine was
not better than conventional treatment
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Why EBM?
Increasingly new evidence (1 million new publications/year)
should lead to major changes in patients care Traditional CME does
not improve clinical performanceEBM can keep the physician up to
date(Sackett 1999, Geyman 2000)
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How to do an appraisal ?By asking questions:
Is it Valid ?Is it Important ?Is it Aplicable ?
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PROGNOSTIC STUDYIs this evidence about prognosis valid ?
1. Was a defined, representative sample of patients assembled at
a common (usual early) point in the course of their disease ? 2.
Was patient follow-up sufficiently long and complete ? 3. Were
objective outcome criteria applied in a blind fashion ? 4. If sub
groups with different prognosis are identified: - Was there
adjustment for important prognostic factors? - Was there validation
in an independent group of test-set patients?
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Valid ?1. Was a defined, representative sample of patients
assembled at a common (usual early) point in the course of their
disease ?Ideally : entire population who ever live who developed
the disease
How Close the report approaches to Ideal ?How the disease was
defined ?How the participants were assembled ?From what point in
the disease should patients be followed ?Inception cohortException
if only learn about late stage in the disease
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Valid ?2. Was patient follow-up sufficiently long and complete
?
Ideally : every patient in the inception cohort would be
followed until they fully recover or develop one of the other
disease outcomes
Study prognosis 100 patients, 4 die, 16 lost to follow upA Crude
case-fatality rate 4,8 % (4/84 x100%)
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Valid ? 3. Were objective outcome criteria applied in a blind
fashion ?
Diseases affect patients; some are easy to spot and some are
more subtle.
Extreme outcomes ; death or full recovery. (easy to detect)
More difficult between them; rediness to work, intensity of
residual paint.
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Valid ?4. If sub groups with different prognosis are identified:
- Was there adjustment for important prognostic factors? - Was
there validation in an independent group of test-set patients?
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Is This valid evidence about prognosis important ?How likely are
the outcomes over time ?
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Important ?How precise are the prognostic estimates ?The text,
tables, graphics of a proper prognostic study include the
confidence intervals for estimates of prognosis
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Can we apply this valid, important evidence about prognosis to
our patient?Are the study patients similar to our own ?Are the
study patients so different from ours that we should not use the
result at all in making prediction for our patients?
Will this evidence make a clinically important impact onour
conclusions about what to offer or tell our patient ?
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Diagnosis
Was the test compared blindly with a gold standard?Was there an
adequate spectrum of disease?Was the referral pattern described?Was
the description of the tests clear enough to reproduce it?Was the
test reproducible (observer agreement)?Was contribution of the
tests to overall diagnosis assessed?
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Therapy
Was the assignment really randomized?Were clinically important
outcomes assesses objectively?Was the treatment feasible to your
practice?Were their at least 80% follow up of subjectsWere both
statistical and clinical significant considered?If the study was
negative the power assessed?
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ETIOLOGY
Was the type of study strong?
(RCT>Cohort>case-control>cross-sectional)
Was the assessment of exposure and outcome free of bias (blinded
assessors)?
Were both association statistically and clinically
significant?Was the association consistent across studies?Was cause
shown to precede the effect?Was there a dose response
relationship?
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Evidence-Based Guidelines Effectiveness of Clinical
InterventionLevelType of evidence
IaMeta-analysis of randomized trialIbAt least one randomized
trialIIaWell-designed, controlled studyIIbWell-designed,
quasi-experimental studyIIIDescriptive and comparative
studies.IVNon random study.VCase serial, expert panel /
committee
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Recommendations On Clinical InterventionGradeNature of
Recommendation
AIa + Ib / ( > I )BIa / IbCIIa / IIbDIII EIV / V
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