Critical appraisal of randomized controlled trial

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What is Critical What is Critical Appraisal?Appraisal?

CRITICAL APPRAISALCRITICAL APPRAISAL

==

QUALITY ASSESSMENTQUALITY ASSESSMENT

What is quality?What is quality? quality is a complex concept or ‘construct’.quality is a complex concept or ‘construct’.

can be acknowledged without difficulty,can be acknowledged without difficulty, but it is not easy to define or measure. but it is not easy to define or measure.

Quality means different Quality means different things to different peoplethings to different people

11--The external validity =The external validity =

ApplicabilityApplicability==

GeneralisabilityGeneralisability the preciscion and extent to which it is the preciscion and extent to which it is

possible to generalise the results of the possible to generalise the results of the

trial to other settingstrial to other settings

Is related to the definition of well-formulateIs related to the definition of well-formulate

questionsquestions : : population, intervention, outcomepopulation, intervention, outcome

It determine byIt determine by

inclusion and exclusion criteriainclusion and exclusion criteria

22-The internal validity :-The internal validity :

thethe degree to which the trial design, degree to which the trial design, conduct, analysis, and presentation conduct, analysis, and presentation have minimized or avoided have minimized or avoided systematicsystematic

biasesbiases..

Sources of bias in trials of Sources of bias in trials of healthcare interventionshealthcare interventions

selection biasselection bias performance biasperformance bias attrition biasattrition bias detection bias detection bias

Sara Mortaz HejriSara Mortaz Hejri

Randomization =Randomization =allocation concealmentallocation concealment

Even when the allocation codes Even when the allocation codes are kept in sealed opaque are kept in sealed opaque envelopes, investigators, for envelopes, investigators, for instance, can look through the instance, can look through the envelopes using powerful lights envelopes using powerful lights or even open the envelope using or even open the envelope using steam and reseal it without steam and reseal it without others noticing.others noticing.

allocation concealment is rarely allocation concealment is rarely reported and perhaps rarely reported and perhaps rarely implemented in RCTs.implemented in RCTs.

A recent study showed that A recent study showed that allocation concealment was allocation concealment was reported in less than reported in less than 10%10% of of articles describing RCTs articles describing RCTs published in prominent journals published in prominent journals in in fivefive different languages different languages

Simple randomisation

Block randomisation

GP Practice 1

GP Practice 2

Stratified randomisation

inadequate :inadequate :

- the use of case record numbers,- the use of case record numbers,

-dates of birth or day of the week, -dates of birth or day of the week,

Even when the trials are described as Even when the trials are described as double-blind, mostly do not provide double-blind, mostly do not provide adequate information on adequate information on how blinding how blinding was achievedwas achieved or statements on the or statements on the perceived success (or failure)perceived success (or failure) of of double-blinding effortsdouble-blinding efforts

3-3-The appropriatenessThe appropriateness

of data analysis and of data analysis and

presentation. presentation.

44--The ethical implicationsThe ethical implications of the intervention they of the intervention they evaluateevaluate

intention to treat analysisintention to treat analysis:: all the study participants are included in the all the study participants are included in the

analyses as part of the groups to which analyses as part of the groups to which they were randomised regardless of they were randomised regardless of whether they completed the study or not. whether they completed the study or not.

Bias in non rctBias in non rct

randomisationrandomisation is the only means of is the only means of allocation that controls for allocation that controls for unknown unknown and unmeasured confounders as well and unmeasured confounders as well as those that are known and as those that are known and measured measured

It is possible to control for It is possible to control for confounders that are confounders that are knownknown and and measured in observational studies, measured in observational studies, such as case-control and cohort such as case-control and cohort studies by studies by matching.matching.

TOOLS:TOOLS:

Checklist :Checklist : the components are the components are evaluated separately and do not have evaluated separately and do not have numerical scores attached to themnumerical scores attached to them

Scale:Scale: each item is scored numerically each item is scored numerically and an overall quality score is and an overall quality score is generated.generated.

JADADJADAD• easy and quick to use easy and quick to use (it takes less than five (it takes less than five

minutes to score a trial report)minutes to score a trial report)

• provides consistent measurements provides consistent measurements has construct validity has construct validity

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It has been shown that studies It has been shown that studies that obtain that obtain 2 or less2 or less points are points are likely to produce treatment likely to produce treatment effects which are effects which are 35% larger35% larger than those produced by trials than those produced by trials with 3 or more points.with 3 or more points.