How to Appraise Therapy

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Principles in critical appraisal

Critical appraisal of primary research (clinical trial) involvesthree overall questions:

Question 1: What is the PICOof the study, and

is it close enough to your PICO?

Question 2: How wellwas the study done?

Question 3: What do the results meanand couldthey

have been due to chance?


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Sir Archie Cochrane

Dave Sack

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MAN IN EBP


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1. Formulate clinical problems in answerable questions

2. Searchthebestevidence: use internet or other on-

line database for current evidence

3. Critically appraise the evidence for

Validity (was the study valid?)

Importance (were the results clinically important?) Applicability(could we apply to our patient?)

4. Apply the evidence to patient

Steps in EBP

VIA

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Treatment


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1. Was the assignment of patients to treatment randomized?

2. Was the randomization conclealed?

3. Were the groups similiar at the start of the trial?

4. Was follow-up of patients sufficiently long and complete?

5. Were all patients analyzed in the groups to which they wererandomized?

Some finer points :

6. Were patients, clinicians, and study personnel kept blind totreatment?

7. Were groups treated equally, apart from the experimentaltherapy?

Is this evidence about treatment valid?


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1. What is the magnitude of the treatment effect?

2. How precise the estimate of the treatment

effect?

Is this valid evidence about treatment

important?


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1. Is our patient so different from those in thr study that

its results cannot apply?

2. Is the treatment feasible in our setting?

What are our patients potential benefits and harms

from the therapy?

3. What are our patients potential benefits and harms

from the therapy?

4. What are our patients values and explectations for

both the outcome we are trying to prevent and the

treatment we are offering?

Is this valid and important evidence applicable

to our patient?


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Internal Validity: RAMMbo

RRecruitment : were the subjects representative?(See Methods)

AAllocation : was the allocation randomised andconcealed? (See Methods)

MMaintenance : did the groups have equal co-intervention and adequate follow up?

( See Methods & Results)

MboMeasurement, blinding, objectivity : were the subjects andassessors kept blind to which treatmentwas being received and/or were the

measures objective (See Methods)


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RRecruitment : Were the subjects representative ofthe target population?

* The best way to ensure that study groups are representative is to:

@Recruit potential subject sequentially and clearly describe the sourceof patients

@Only apply exclusion criteria that are relevant to study methods

@See the size of study groups

* Where do I find the information?

Early in the Methods should tell you how patients were selected forthe study


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AAllocation : was the treatment allocation concealed beforerandomisation and were the groups comparable at the

start of trial?

@ Match groups as closely as possible in every way except for the

intervention

@ Allocation concealment used for randomisation :

* centralised computer randomisation (the best one)

* sealed envelopes: not as good because the allocation is not as

well concealed

*Where do I find the information?@ Methods: should tell you how patient were allocated and

whether or not randomisation was concealed

@Results: see table of Baseline characteristics


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MMaintenance : Was the comparable status of thestudy groups maintained through equal

management and adequate follow up?

Equal management:

@ the only difference between the groups is factor

being tested

@ use an identical measurement strategy for everyone

Adequate follow-up:

@ subjects at the start = subjects at the end

@ subject are analysed in the groups that they started

* Where do I find the information?

@ look in the Methodsfor the precise protocol

@ look in Resultsfor any further information and flowchart study


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MboMeasurement, blinding, objectivity :Were the outcomes measured with blinded subjects and assessors

and/or objective measures?Blinding

Best -- Double blind trial : subject and investigators (outcome

assessors) both unware of group allocation

Moderate -- Single blind trial: either the subject or investigators areunware of group allocation

Worst -- Not blinded: subject and investigators both aware of group

allocation

* Where I do find the information?

Methodssection should describe how the outcome was assessed

and whether the assessor/s were aware of the patients treatment


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Question 3: What do the results mean and could

they have been due to chance?

* Outcome measures1. Binary outcomes:

Relative Risk/RR, Absolute Risk Reduction/ARR

Relative Risk Reduction/RRR

Number Needed to Treat/NNT

2. Continuous outcomes

* Are the results real and relevant?

P-values ( hypothesis testing)

Confidence Interval/CI ( estimation)


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TH NKYOU

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How to Appraise Therapy