Homework answers / question archive / HSCI270 M5 CASP Checklist: 11 questionsto help you make sense of a Case Control Study How to use this appraisal tool: Three broad issues need to be considered when appraising a case control study:  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

HSCI270 M5 CASP Checklist: 11 questionsto help you make sense of a Case Control Study How to use this appraisal tool: Three broad issues need to be considered when appraising a case control study:  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

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HSCI270 M5 CASP Checklist: 11 questionsto help you make sense of a Case Control Study

How to use this appraisal tool: Three broad issues need to be considered when appraising a

case control study:

 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. Case Control 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

Critical Appraisal Skills Programme (CASP) part of Oxford Centre for Triple Value Healthcare Ltd www.casp-uk.net

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Section A: Are the results of the trial valid?

1. Did the study address a

clearly focused issue?

Yes HINT: An issue can be ‘focused’ In terms of

• the population studied

• Whether the study tried to detect a

beneficial or harmful effect

• the risk factors studied

Can’t Tell

No

Comments:

2. Did the authors use an

appropriate method to

answer their question?

Yes HINT: Consider

• Is a case control study an appropriate

way of answering the question under

the circumstances

• Did it address the study question

Can’t Tell

No

Comments:

Paper for appraisal and reference:............................................................................................................

3

Is it worth continuing?

3. Were the cases recruited in

an acceptable way?

Yes HINT: We are looking for selection bias

which might compromise validity of the

findings

• are the cases defined precisely

• were the cases representative of a

defined population (geographically

and/or temporally)

• was there an established reliable

system for selecting all the cases

• are they incident or prevalent

• is there something special about the

cases

• is the time frame of the study

relevant to disease/exposure

• was there a sufficient number of

cases selected

• was there a power calculation

Can’t Tell

No

Comments:

4. Were the controls selected in

an acceptable way?

Yes HINT: We are looking for selection bias

which might compromise the

generalisability of the findings

• were the controls representative of the

defined population (geographically

and/or temporally)

• was there something special about

the controls

• was the non-response high, could

non-respondents be different in

any way

• are they matched, population

based or randomly selected

• was there a sufficient number of

controls selected

Can’t Tell

No

Comments:

4

5. Was the exposure accurately

measured to minimise bias?

Yes HINT: We are looking for measurement,

recall or classification bias

•was the exposure clearly defined and

accurately measured

• did the authors use subjective or

objective measurements

• do the measures truly reflect what

they are supposed to measure (have

they been validated)

• were the measurement methods

similar in the cases and controls

• did the study incorporate blinding

where feasible

• is the temporal relation correct

(does the exposure of interest

precede the outcome)

Can’t Tell

No

Comments:

6. (a) Aside from the

experimental intervention,

were the groups treated

equally?

HINT: List the ones you think might be

important, that the author may have

missed

• genetic

• environmental

• socio-economic

List:

6. (b) Have the authors taken

account of the potential

confounding factors in the

design and/or in their

analysis?

Yes HINT: Look for

• restriction in design, and techniques e.g.

modelling, stratified-, regression-, or

sensitivity analysis to correct, control or

adjust for confounding factors

Can’t Tell

No

Comments:

5

Section B: What are the results?

7. How large was the treatment effect? HINT: Consider

• what are the bottom line

results

• is the analysis appropriate to

the design

• how strong is the association

between exposure and

outcome (look at the odds

ratio)

• are the results adjusted for

confounding, and might

confounding still explain the

association

• has adjustment made a big

difference to the OR

Comments:

8. How precise was the estimate of the treatment

effect?

HINT: Consider

• size of the p-value

• size of the confidence intervals

• have the authors considered all the

important variables

• how was the effect of subjects

refusing to participate evaluated

Comments:

6

9. Do you believe the results? Yes HINT: Consider

• big effect is hard to ignore!

• Can it be due to chance, bias, or

confounding

• are the design and methods of this

study sufficiently flawed to make the

results unreliable

• consider Bradford Hills criteria (e.g. time

sequence, does-response gradient,

strength, biological plausibility)

No

Comments:

Section C: Will the results help locally?

10. Can the results be applied

to the local population?

Yes HINT: Consider whether

• the subjects covered in the study could

be sufficiently different from your

population to cause concern

• your local setting is likely to differ

much from that of the study

• can you quantify the local benefits and

harms

Can’t Tell

No

Comments:

11. Do the results of this study

fit with other available

evidence?

Yes HINT: Consider

• all the available evidence from RCT’s

Systematic Reviews, Cohort Studies,

and Case Control Studies as well, for

consistency

Can’t Tell

No

Comments:

Remember One observational study rarely provides sufficiently robust evidence to recommend changes to

clinical practice or within health policy decision making. However, for certain questions observational

studies provide the only evidence. Recommendations from observational studies are always stronger

when supported by other evidence.