CASP Checklist: 12 questions to help you make sense of a Cohort Study
How to use this appraisal tool: Three broad issues need to be considered when appraising a
cohort study:
Are the results of the study valid? (Section A)
What are the results?
(Section B)
Will the results help locally?
(Section C)
The 12 questions on the following pages are designed to help you think about these issues
systematically. The first two 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. Cohort Study) Checklist. [online]
Available at: URL. Accessed: Date Accessed.
©CASP this work is licensed under the Creative Commons Attribution – Non-CommercialShare A like. To view a copy of this license, visit http://creativecommons.org/licenses/by-ncsa/3.0/ www.casp-uk.net
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Paper for appraisal and reference:.........................................................................................................
Section A: Are the results of the study valid?
1. Did the study address a clearly
focused issue?
Yes
Can’t Tell
No
HINT: A question can be ‘focused’
in terms of
• the population studied
• the risk factors studied
• is it clear whether the study tried to
detect a beneficial or harmful effect
• the outcomes considered
Comments: The study was conducted
in order to compare the HRQOL outcomes for patients treated with Active Surveillance (AS)
and Radical Prostatectomy (RP) after diagnosis of localised prostate cancer. This was conducted in multi-centers in
Germany, where physicians would enroll the newly diagnosed patient to the study prior to treatment. To study the
HRQOL outcomes at 6 month intervals, a validated instrument was used for HRQOL outcomes alongside information on
clinical data using D'amico risk categories and Charlson Comorbidity index. The outcomes from the questionaires where
divided into 5 functional scales looking at global quality of life, physical, role, smotional, cognitive and social functioning.
Descriptive and longitudinal modeling were performed to determine a a clinically significant difference in terms of
HRQOL outcomes between the two treatments. This would help imform patient's choice in choosing treatments as
previous studies have highlighted the comparative oncological outcome for AS and RP.
2. Was the cohort recruited in
an acceptable way?
Yes
Can’t Tell
No
HINT: Look for selection bias which might
compromise the generalisability of the
findings:
• was the cohort representative of a
defined population
• was there something special about the
cohort
• was everybody included who should
have been
Comments: The study collected HRQOL data from newly diagnosed patients with localised prostate cancer in Germany. From the
3169 patients enrolled in the HAROW study, only those that received AS or RP with localised prostate cancer( T1-2, N0,
M0) were included. The study excluded patients treated with other common treatments such as radiotheraphy, hormone
therapy and waitful watching The study overall analysed 961 patients.Overal 405 patients with AS and 556 patients
receiving RP were included in the study. The study chose multicentre apporach to mimic a 'real world' situation where the
treatment decision was decided between the physician and patient, rather than through randomization. It was explained
that randomisation in trials to do with prostate cancer were rare and have previously been discountinued due to lack of
participation. Therfore this study is subject to selection bias. The cohort studies was representative of those who get
prostate cancer worldwide,middle aged men ranging from <50 - >70 years, Those who chose not to participate were
excluded, but treated accordingly.
Is it worth continuing?
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3. Was the exposure accurately
measured to minimise bias?
Yes
✔
Can’t Tell
No
Comments:
HINT: Look for measurement or
classification bias:
• did they use subjective or objective
measurements
• do the measurements truly reflect what
you want them to (have they been
validated)
• were all the subjects classified
into exposure groups using the
same procedure
The study does not state how patients were diagnosed with prostate cancer but only that physicians used the D'amico risk categories to
classify patients into level of prostate cancer. The study describes the criteria for AS given to the physicians, which followed
recommendations by the largest published prospective study of AS known as the PRIAS study. This was due to the study being conducted in
July 2008, at which time official guidelines for AS were not in place. Due to AS being a dynamic treatment with frequent clinical follow up, the
patients whose prostate cancer progressed and changed their treatment, were still included in the study up till the time AS was terminated.
RP was done through open procedures as was common in the time this study was conducted. There is no further information on
investigations or procedures done in order to diagnose the patients in this study but since this is a part of a larger study, information will be
included in the references
4. Was the outcome accurately
measured to minimise bias?
Yes
Can’t Tell
No
✔
HINT: Look for measurement or
classification bias:
• did they use subjective or objective
measurements
• do the measurements truly reflect what
you want them to (have they been
validated)
• has a reliable system been
established for detecting all the cases (for
measuring disease occurrence)
• were the measurement
methods similar in the different groups
• were the subjects and/or
the outcome assessor blinded to
exposure (does this matter)
Comments:
The main outcome of HRQOL outcomes for patients following either AS or RP for localised prostate cancer.
This was assessed using the European Organisation for Research and Treatment of Cancer quality of life
questionnaire 30-iten core (EORTC QLQ-C30). This is an established cancer specific measure of HRQOL
and has been used in previous international studies. It has demonstrated good psychometric properties and
clinical validity in earlier studies, therefore appropriate in this study. The study also employed a general
sociodemographic data in order to account for confounding, which was used in a covariance analysis. Both
these were completed before treatment and biannuly and were sent postally.
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5. (a) Have the authors identified
all important confounding
factors?
Yes
✔
Can’t Tell
HINT:
• list the ones you think might be
important, and ones the author missed
No
Comments: Through the use of the sociodemographic survey and linear regression models, the study has
included some important confounders such as age, co-morbidities and living with a partner. It
also acknowledges confounders that it did not account for such as patients; personality and
preferences due to the nature of the study being non-randomised. But the study does not
account for ethnicity, income or education which could result in confounding.
5. (b) Have they taken account of
the confounding factors in the
design and/or analysis?
Yes
✔
Can’t Tell
No
HINT:
• look for restriction in design, and
techniques e.g. modelling, stratified-,
regression-, or sensitivity analysis to
correct, control or adjust for confounding
factors
Comments: The results were analysed by a linear hierarchical regression model taking into account
of the confounders.The intraclass correlation coefficient was calculated in order to
highlight differences in the HRQOL outcome between patients. Longitudinal multilevel
modelling was also chosen to estimate and explain the trends in HRQOL over the
timeline of the study.
6. (a) Was the follow up of
subjects complete enough?
Yes
Can’t Tell
✔
No
6. (b) Was the follow up of
subjects long enough?
HINT: Consider
• the good or bad effects should have
had long enough to reveal
themselves
• the persons that are lost to follow-up
may have different outcomes than
those available for assessment
• in an open or dynamic cohort, was
there anything special about the
outcome of the people leaving, or the
exposure of the people entering the
cohort
Yes
Can’t Tell
No
✔
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Comments:
Although the study was conducted for 5 years, the analysis of the data was only done with data for 3.5 years
due to rate of dropout. The reasons for drop-out is not detailed apart for those under AS. 112 participants
switched to a deferred treatment and considerable number chose an active treatment. The analysis were
only done with data till AS was terminated. This is due to the criteria for AS, as there was discontinuation of
AS due for progression of disease through the specified measurements. RP was a definitive active treatment
therefore there was no change in exposure.
Section B: What are the results?
7. What are the results of this study?
HINT: Consider
• what are the bottom line
results
• have they reported the rate or
the proportion between the
exposed/unexposed, the
ratio/rate difference
• how strong is the association
between exposure and
outcome (RR)
• what is the absolute risk
reduction (ARR)
Comments: The study revealed that AS scored higher for role, emotional and social functioning compared to RP
patients but only up till 1 year after diagnosis. The results were statistically significant but not
clinically. Prostate cancer treated with AS compared to RP had similar or sometimes higher level of
oeverall HRQOL as well as role, emotional and social function during the follow up time of 3.5 years.
The only clinically significant difference between the treatments was for social functioning for AS up
to 6 months after diagnosis. patients treated with RP start off with a lower HRQOL at baseline and
recover to the level of AS patients aorund 2 years after diagnosis.
8. How precise are the results?
HINT:
• look for the range of the confidence
intervals, if given
Comments:
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9. Do you believe the results?
Yes
✔
Can’t Tell
No
HINT: Consider
• big effect is hard to ignore
• can it be due to bias, chance or
confounding
• are the design and methods of this
study sufficiently flawed to make the
results unreliable
• Bradford Hills criteria (e.g. time
sequence, dose-response gradient,
biological plausibility, consistency)
Comments: The study was non-randomised therefore is subject to bias. To account for chance, intraclass
correlation coefficients were generated and provided insight into the variation of HRQOL between
patients. Confounders were accounted for through linear regression models.
The results are comparable to previous studies looking at HRQOL outcomes between AS and RP.
Section C: Will the results help locally?
10. Can the results be applied to
the local population?
Yes
✔
Can’t Tell
No
HINT: Consider whether
• a cohort study was the appropriate
method to answer this question
• the subjects covered in this study could
be sufficiently different from your
population to cause concern
• your local setting is likely to differ
much from that of the study
• you can quantify the local benefits and
harms
treatments explored in this study are the recommended ones for localised prostate cancer in the UK. Although the criteria for diagnosis was not detailed, the
Comments: The
strategy for recommending AS is comparitive to the NICE guidelines. The healthcare system of Germany is similar to the NHS as it is they are both universal
multi-payer healthcare systems. Although the way in which the multi-centres diagnosed could be different, they all followed the D'amico calssification. and
treatments were standardised and described for both RP and AS but surgery could vary from centre to center. A cohort is useful to look at HRQOL outcomes of
patients following treatments for quality of life, as this is a subjective measure and allows a longer time of follow up. Since this study was conducted in Europe
and included a similar population to the UK, the results can be comparable. the study has show the subjective experiences of the patients and so will help
physicians to make shared decisions with patients.
11. Do the results of this study fit
with other available
evidence?
Yes
Can’t Tell
✔
✔
No
Comments: The results of this study was paralleled i with the Vanagas et al. study. Where patients under AS had higher
role, emotional and social
functioning compared to RP. But in the Vanagas study they had statistically and clinically significant improvements for AS compared to
RP but they also used the EORTC QOLQ-C30, therefore it is a reliable comparison.Jeldres et al found that physical, social and role
functioning for RP patients up to 6 months after treatment decision but in this study only social functioning revealed a clinically relavent
difference after diagnosis. In the PIVOT study they found that RP had higher limitations in terms of activities of daily living, which was
similar to this studies findings, that role functioning was worse for RP until 2 years after treatment.
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12. What are the implications of
this study for practice?
Yes
Can’t Tell
No
Comments:
HINT: Consider
one observational study rarely
provides sufficiently robust
evidence to recommend changes
to clinical practice or within health
policy decision making
• for certain questions,
observational studies provide the
only evidence
• recommendations from
observational studies are always
stronger when supported by other
evidence
•
The findings of this study was comparable to previous studies looking at specific HRQOL outcomes. This
study also found that patients with co-morbidities has overall lower HRQOL which is also confirmed by large
number of studies and should be considered when making treatment decisions. Since there was so clinically
relevant results therefore, no recommendations can be made to current guideline as even though RP initially
has a lower HRQOL, patients recover up to the level of AS patients withing 1-2 years after diagnosis. treatment
decision should be made with a consideration for these HRQOL outcomes as well as age and co-morbidities.
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