How to Use the CASP (Critical Appraisal Skills Programme) RCT Checklist

The CASP RCT Checklist is a structured tool to critically appraise Randomized Controlled Trials (RCTs) for validity, reliability, and clinical relevance. It consists of 11 key questions divided into three sections:
  1. Validity (Are the results trustworthy?)
  2. Results (What are the findings?)
  3. Applicability (Can the results be applied to your context?)

? Step 1: Download the CASP RCT Checklist

? Step 2: Appraise the Study Using the 11 Key Questions

A. Validity (Questions 1-6)

1. Did the trial address a clearly focused research question?
  • ✔ Look for PICO elements (Population, Intervention, Comparison, Outcome).
  • ❌ If the question is vague (e.g., "Does treatment X work?"), it’s a weakness.
2. Was the assignment of participants randomized?
  • ✔ Check if randomization was truly random (e.g., computer-generated).
  • ❌ If randomization is unclear or not mentioned, downgrade credibility.
3. Were participants and researchers blinded (masked)?
  • ✔ Look for double-blinding (participants & assessors unaware of treatment).
  • ❌ If blinding was impossible (e.g., surgery vs. drug), note potential bias.
4. Were all participants accounted for at the study’s conclusion?
  • ✔ Check attrition/dropout rates (≤20% is acceptable).
  • ✔ Was Intention-to-Treat (ITT) analysis used?
  • ❌ High dropout (>20%) or per-protocol analysis weakens reliability.
5. Were the groups similar at baseline?
  • ✔ Compare baseline characteristics (age, gender, disease severity).
  • ❌ Major imbalances suggest flawed randomization.
6. Were participants treated equally apart from the intervention?
  • ✔ Check if co-interventions (e.g., additional drugs) were balanced.
  • ❌ If one group received extra care, results may be biased.

B. Results (Questions 7-9)

7. How large was the treatment effect?
  • ✔ Look for effect size (e.g., Relative Risk, Odds Ratio, Mean Difference).
  • ✔ Check confidence intervals (CI)—narrow CIs = more precise results.
8. How precise was the estimate of the treatment effect?
  • ✔ If 95% CI crosses "no effect" (RR=1 or MD=0), results may not be significant.
9. Were all important outcomes considered?
  • ✔ Check if primary & secondary outcomes were pre-specified.
  • ❌ If key outcomes (e.g., side effects) are missing, downgrade quality.

C. Applicability (Questions 10-11)

10. Can the results be applied to your local population?
  • ✔ Compare study participants with your patients (age, comorbidities, setting).
  • ❌ If the study used highly selected patients, generalizability may be limited.
11. Were all clinically important outcomes considered?
  • ✔ Does the study report patient-relevant outcomes (e.g., survival, QoL)?
  • ❌ If only surrogate markers (e.g., lab values) are used, clinical relevance is unclear.

? Step 3: Summarize Your Appraisal

After answering all 11 questions, categorize the study as: ✅ High Quality (Mostly "Yes" answers, low risk of bias) ⚠ Moderate Quality (Some "Unclear" or minor flaws) ❌ Low Quality (Multiple "No" answers, high risk of bias)

? Example CASP Appraisal

Question Answer Comments
1. Focused question? ✔ Yes Clear PICO: "Does Drug X reduce mortality in heart failure?"
2. Randomized? ✔ Yes "Computer-generated randomization"
3. Blinded? ❌ No Open-label trial (high risk of bias)
4. All participants accounted for? ✔ Yes 5% dropout, ITT analysis used
5. Groups similar at baseline? ✔ Yes Balanced age, gender, disease severity
6. Treated equally? ✔ Yes No co-interventions reported
7. Treatment effect size? ✔ Yes RR 0.70 (95% CI 0.55–0.89)
8. Precise estimate? ✔ Yes CI does not cross 1 (significant)
9. All outcomes reported? ❌ No Adverse effects missing
10. Applicable locally? ⚠ Unclear Study in Europe; local population differs
11. Clinically important outcomes? ✔ Yes Mortality & hospitalization reported
Final Rating: ⚠ Moderate Quality (Lack of blinding & missing harms data)

? When to Use CASP RCT Checklist?

✔ Systematic reviews (to assess included studies). ✔ Clinical practice (to decide if evidence is trustworthy). ✔ Journal clubs (teaching critical appraisal skills).

? Comparison with Other Tools

Tool Best For Key Difference
CASP RCT Quick, structured appraisal Focuses on clinical relevance
Cochrane RoB 2 Detailed bias assessment More rigorous for systematic reviews
SIGN Checklist Guideline development Includes study design quality ratings

Final Tips

✅ Use alongside CONSORT to check reporting completeness. ✅ Involve multiple reviewers to reduce bias in appraisal. ✅ Document justifications for transparency. Would you like a blank CASP checklist template for your reviews?