You have just read an article claiming a "breakthrough" treatment for a condition you manage regularly, but you are thinking: "How do I know if this research is actually any good?"
This is where CASP comes in. CASP (Critical Appraisal Skills Programme) checklists are a series of checklists involving prompt questions to help you evaluate research studies. They are designed to help systematically assess the trustworthiness, value, and relevance of published research studies.
- Are the results of the study valid? (Assesses methodological rigour and bias).
- What are the results? (Examines the reported outcomes and their clinical importance).
- Will the results help locally (in my setting)? (Evaluates the relevance and applicability of the findings to a specific context).
CASP provides free checklists for the most common types of research you'll encounter:
- Systematic Reviews with Meta-Analysis of Observational Studies
- Systematic Reviews with Meta-Analysis of RCTs
- Randomised Controlled Trial / RCT
- Systematic Review
- Qualitative Studies
- Cohort Study
- Diagnostic Study
- Case Control Study
- Economic Evaluation
- Clinical Prediction Rule
- Cross-Sectional Studies
Download PDF or Word versions at: https://casp-uk.net/casp-tools-checklists/
How to Use CASP Checklists in 10 Minutes
The Three Sections
As already mentioned, every CASP checklist has three parts:
Section A: Are the results valid? (Screening questions)
Section B: What are the results? (Detailed questions)
Section C: Will the results help locally? (Applicability)
Section A: Screening Questions (2 minutes)
These are your "deal breakers." If the study fails here, you can stop—it's not worth continuing.
Question 1: Did the review address a clearly focused question?
Look for PICO:
- Population: Who was studied?
- Intervention: What was done?
- Comparison: Compared to what?
- Outcome: What did they measure?
Example of a good focused question: "In adults with Type 2 diabetes (P), does metformin (I) compared to placebo (C) reduce cardiovascular events (O)?"
Example of a poor question: "Does medication help diabetes?" (Too vague!)
If YES → Continue. If NO → Stop here, study is too broad/unclear
Question 2: Did the authors look for the right type of papers?
For a systematic review about treatment effectiveness, you'd want to see:
- ✅ Randomised controlled trials (RCTs)
- ✅ High-quality studies
- ✅ Relevant to the question
If they are including case reports or opinion pieces for a treatment question, that's a red flag.
If YES → Continue to Section B. If NO → Major concerns about reliability
Time check: 2 minutes spent. Should you continue? If both screening questions = YES, proceed.
Section B: Detailed Assessment (5 minutes)
Now you're diving deeper into the quality of the research.
Question 3: Do you think all the important, relevant studies were included?
Look for:
- ✅ Comprehensive search strategy (multiple databases)
- ✅ Clear inclusion/exclusion criteria
- ✅ Hand searching of reference lists
- ✅ Attempts to find unpublished studies
- ❌ Only searched one database = incomplete
- ❌ Only English language papers = potential bias
Question 4: Did the review's authors do enough to assess the quality of included studies?
Look for:
- ✅ Used validated quality assessment tools (like CASP!!)
- ✅ At least two reviewers assessed each study independently
- ✅ Quality scores reported
- ❌ No quality assessment = you don't know if they included junk studies
Question 5: If the results have been combined, was it reasonable to do so?
Check:
- ✅ Studies were similar enough to combine (similar populations, interventions, outcomes)
- ✅ Statistical heterogeneity assessed
- ❌ Combined apples and oranges (e.g., different age groups, different interventions)
Question 6: What are the overall results of the review?
Now you're getting to the findings:
- What is the main result?
- Is there a clear effect size?
- Are confidence intervals reported?
- How certain are the results?
Example: "Intervention reduced mortality by 20% (95% CI: 10-30%)" = clear, useful result
Question 7: How precise are the results?
Look at confidence intervals:
- Narrow = precise, confident
- Wide = uncertain, less reliable
Example:
- Precise: Risk reduction 20% (CI: 18-22%) = we're pretty sure it's around 20%
- Imprecise: Risk reduction 20% (CI: 2-38%) = could be anywhere from barely effective to very effective
Time check: 7 minutes total. Almost done!
Section C: Will the results help locally? (3 minutes)
This is where you decide: "Should I change my practice?"
Question 8: Can the results be applied to the local population?
Consider:
- Is your patient population similar to the study population?
- Are there important differences (age, comorbidities, setting)?
- Is the intervention feasible in your setting?
Example: Study in a community settings with limited resources might not apply to an acute hospital setting with intensive monitoring.
Question 9: Were all important outcomes considered?
Check:
- Did they measure what matters to patients?
- Did they only report positive outcomes (cherry-picking)?
- What about adverse effects, quality of life, cost?
Question 10: Are the benefits worth the harms and costs?
The final question:
- What is the balance of benefits vs risks?
- Is it cost-effective?
- What do patients value?
- Are there alternative interventions?
Time check: 10 minutes total. Done!
CASP Checklists for Different Study Types
Use when: Evaluating treatment effectiveness studies
Key screening questions:
- Did the trial address a clearly focused issue?
- Was the assignment of patients to treatments randomised?
- Were all patients who entered the trial properly accounted for at its conclusion?
- ❌ No randomisation
- ❌ High dropout rates (>20%)
- ❌ No intention-to-treat analysis
- ❌ Unblinded when blinding was possible
Cohort Study Checklist
Use when: Looking at prognosis, outcomes, or risk factors
Key screening questions:
- Did the study address a clearly focused issue?
- Was the cohort recruited in an acceptable way?
- Was the exposure accurately measured to minimise bias?
- ❌ Selected cohort (not representative)
- ❌ Short follow-up period
- ❌ High loss to follow-up
- ❌ No adjustment for confounding factors
Qualitative Research Checklist
Use when: Understanding patient experiences, perspectives, or complex phenomena
Key screening questions:
- Was there a clear statement of the aims?
- Is a qualitative methodology appropriate?
- ❌ Quantitative question disguised as qualitative
- ❌ No description of methods
- ❌ Researcher bias not considered
- ❌ No participant quotes/data
Case Control Study Checklist
Use when: Investigating causes of disease or rare outcomes
Key screening questions:
- Did the study address a clearly focused issue?
- Did the authors use an appropriate method to answer their question?
- Were the cases recruited in an acceptable way?
- ❌ Cases and controls from different populations
- ❌ Recall bias not addressed
- ❌ No matching or adjustment for confounders
- ❌ Small sample size for rare exposure
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