CASP Checklist:
11 questions to help you make sense of a Randomised Controlled Trial
How to use this appraisal tool: Three broad issues need to be considered when appraising a
Are the results of the study valid? (Section A)
What are the results? (Section B)
Will the results help locally? (Section C)
The 11 questions on the following pages are designed to help you think about these issues
systematically. The first three questions are screening questions and can be answered
quickly. If the answer to both is “yes”, it is worth proceeding with the remaining questions.
There is some degree of overlap between the questions, you are asked to record a “yes”,
“no” or “can’t tell” to most of the questions. A number of italicised prompts are given after
each question. These are designed to remind you why the question is important. Record your
reasons for your answers in the spaces provided.
About: These checklists were designed to be used as educational pedagogic tools, as part of a
workshop setting, therefore we do not suggest a scoring system. The core CASP checklists
(randomised controlled trial & systematic review) were based on JAMA 'Users’ guides to the
medical literature 1994 (adapted from Guyatt GH, Sackett DL, and Cook DJ), and piloted with
health care practitioners.
For each new checklist, a group of experts were assembled to develop and pilot the checklist
and the workshop format with which it would be used. Over the years overall adjustments
have been made to the format, but a recent survey of checklist users reiterated that the basic
format continues to be useful and appropriate.
Referencing: we recommend using the Harvard style citation, i.e.: Critical Appraisal Skills
Programme (2018). CASP (insert name of checklist i.e. Randomised Controlled Trial) Checklist.
[online] Available at: URL. Accessed: Date Accessed.
©CASP this work is licensed under the Creative Commons Attribution Non-Commercial-
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Critical Appraisal Skills Programme (CASP) part of Oxford Centre for Triple Value Healthcare Ltd
Section A: Are the results of the trial valid?
1. Did the trial address a clearly
focused issue?
HINT: An issue can be focused In terms of
the population studied
the intervention given
the comparator given
the outcomes considered
Can’t Tell
2. Was the assignment of
patients to treatments
HINT: Consider
how this was carried out
was the allocation sequence concealed
from researchers and patients
Can’t Tell
3. Were all of the patients
who entered the trial
properly accounted for at
its conclusion?
HINT: Consider
was the trial stopped early
were patients analysed in the groups to
which they were randomised
Can’t Tell
Is it worth continuing?
Paper for appraisal and reference:
4. Were patients, health
workers and study personnel
‘blind’ to treatment?
5. Were the groups similar at
the start of the trial
HINT: Consider
other factors that might affect the
outcome, such as; age, sex, social class
6. Aside from the experimental
intervention, were the groups
treated equally?
Can’t Tell
Section B: What are the results?
7. How large was the treatment effect?
HINT: Consider
what outcomes were
Is the primary outcome clearly
what results were found for
each outcome
8. How precise was the estimate of the treatment
HINT: Consider
what are the confidence limits
Section C: Will the results help locally?
9. Can the results be applied to
the local population, or in
your context?
HINT: Consider whether
the patients covered by the trial are
similar enough to the patients to whom
you will apply this
how they differ
10. Were all clinically important
outcomes considered?
HINT: Consider whether
there is other information you would
like to have seen
if not, does this affect the decision
11. Are the benefits worth the
harms and costs?
HINT: Consider
even if this is not addressed by the
trial, what do you think?