umsu ebm harm
TRANSCRIPT
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Evidence BasedMedicine
HARMDr. Juliandi Harahap, MA
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We frequently must make judgments
about whether a medical interventionor an environmental agent is harming
our patient,
e.g.:
Does caeine consumption cause urinaryincontinence
Does living close to hydroelectric power
lines increase the risk of cancer Do statins cause cancer Does e!posure to aluminum cause
al"heimer#s dementia
Do elevated homocysteine levels causecoronary artery disease
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$%&'(&)*+
Risk: the likelihood that people who areexposed to certain factors (risk factors)will subsequently develop a particular
disease. Risk factors: characteristics that are
associated with an increased risk ofbecoming diseased.
Exposure:
ingle point in time: e.g. nuclearaccident
!eriod of time: e.g. cigarette smoking
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&isk factors vs prognostic factors
condition that canbe identi"ed in well
persons and# whenpresent# areassociated with anincreased risk ofacquiring disease
conditions that#when present in
persons alreadyknown to havedisease# areassociated with anoutcome of thedisease
Risk factor: !rognostic factors:
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Dierences between risk andprognosis:
ow probability events &elatively frequentevents
-he event: nset ofdisease
&isk factors are notnecessarily the sameas prognostic factorsfor a given disease
-he event: Death,complications,disability, suering,etc.
/rognostic factorsare not necessarilythe same as riskfactors for a givendisease
&isk /rognosis
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$reatment
E%cacious
&armless
&armful
'ot e%cacious
&armless
&armful
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edical intervention
E%cacious
&arm
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$ow to assess $%&'
s there evidence on cause and e*ectrelationship+
,alidity mportance
-pplicability
$%&' W&+*$00-
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%re the results of this harmstudy valid. /ere there clearly de"ned groups of
patients# similar in all important waysother than exposure to the treatment orother cause+
)deally the best evidence that we can 1ndabout putative harmful agents comes fromsystematic reviews.
ther study designs: randomi"ed trial,cohort, case control study and crosssectional study
&andomi"ation would tend to make the twogroups identical. )t balances the groups for
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%dverse outcome
/resent2case3
%bsent2controls3
-otals
0!posed totreatment
2&4- or cohort3
% 5 %65
7ot e!posed totreatment
2&4- or cohort3
4 D 46D
totals %64 56D %65646D
% group of participants who are e!posed 2a6b3to the putative harmful agent and a group or
participants who aren#t e!posed 2c6d3 to it arefollowed for the development of the outcome of
interest 2a or c3
% 4ohort *tudy
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0. /ere treatments1exposures and clinicaloutcomes measured in the same ways inboth groups (/as the assessment of
outcomes either ob2ective or blinded toexposure)+
When the outcomes assessors aren#tblinded to the e!posure, they may search
harder for the diseases in e!posed groupand identify disease that might otherwisehave been unnoticed
%re the results of this harmstudy valid
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34 cancer 89; 7ocancer
5ong6termollow up
*hort term
89?@ personAyearsof taking 4aantagonist
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3. 8o the results of the harm study ful"llsome of the diagnostic test forcausation+
%re the results of this harm studyvalid
)s it clear that the e!posure preceded theonset of the outcome )s there a doseBresponse gradient )s there any positive evidence from a
Cdechallenge rechallenge study
)s the association consistent from study tostudy
Does the association make biologicalsense
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. /hat is the magnitude of the associationbetween the exposure and outcome
%re the valid results of this harm studyimportant
8i*erent study designs require di*erentmethods for estimating the strength ofassociation between exposure to the
putative cause and the outcome ofinterest
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%dverse outcome
/resent
2case3
%bsent2contro
ls3
-otals
0!posed totreatment
2&4- or cohort3
; @E 8
7ot e!posed totreatment
2&4- or cohort3
; @@E 8
totals ;; 8@FE ;&0%-)G0 &)*+
2&&3 H %(2%653 : 4(246D3&&H8-his means that patients receiving thetreatment are 8 times more likely to
e!perience the outcome as patients not
4ohort *tudy
4ohort *tudy
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%dverse outcome
/resent
2case3
%bsent2contro
ls3
-otals
0!posed totreatment
2&4- or cohort3
% 5 %65
7ot e!posed totreatment
2&4- or cohort3
4 D 46D
totals %64 56D %65646D
DD* &%-) 2&0%-)G0 DD*3& H %D(54
4ase controlstudy
4ase controlstudy
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9R and RR values indicate that there isan increased risk of the adverse outcomeassociated with the exposure
9R and RR ; # the adverse event is nomore likely to occur with than without theexposure to the suspected agent.
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$ow big should the && or & be for us to beimpressed
4ohort
4aseAcontrol & < ?
'inor %dverse event
&& < I
adjustment
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77$ 27umber 7eeded to $arm 3:7umber of patients who need to be e!posed
to the putative causal agent to produce oneadditional harmful event
8 B J/00& ! 28 A &3K77$ H AAAAAAAAAAAAAAAAAAAAAAAAAAAAA
28 A /00&3 ! /00& ! 28 A &3
8 6 J/00& ! 2& A 83K77$ H AAAAAAAAAAAAAAAAAAAAAAAAAAAAA
28 A /00&3 ! /00& ! 2& A 83)f & < 8
)f & L 8
77$ H 8 ( J %(2%653K B J4(246D3
/00& H/atient
0!pected0vent &ate
2the adverseevent rate
among
individualswho are not
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0. /hat is the precision of the estimate ofthe association between the exposureand the outcome
%re the valid results of this harm studyimportant
its precision by examining the
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. s our patient so di*erent from thoseincluded in the study that its resultscannot apply+
0. /hat is our patient=s risk of bene"t andharm from the agent+
7. /hat are our patient=s preferences#concerns and expectations from thistreatment+
3. /hat alternative treatments are
4an this valid and important evidenceabout harm be applied to our patient
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Thank you