Umsu Ebm Harm

7/25/2019 Umsu Ebm Harm..

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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


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


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

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Umsu Ebm Harm