BCACP Clinical Literature Interpretation 3 — Questions and Answers
Question 1: A cohort study follows patients with and without statin use over 10 years to assess cardiovascular events. What measure of association is most appropriate to report?
- Relative risk (RR) (Correct answer)
- Odds ratio (OR)
- Number needed to treat (NNT)
- Hazard ratio (HR) only in case-control studies
Correct answer: Relative risk (RR)
Relative risk is the preferred measure of association in cohort studies with known incidence rates.
Question 2: A study has a wide 95% confidence interval crossing 1.0 for an odds ratio. What does this indicate?
- The result is not statistically significant (Correct answer)
- The result is clinically insignificant
- There is high precision in the estimate
- The intervention is harmful
Correct answer: The result is not statistically significant
A 95% CI for an odds ratio that includes 1.0 indicates no statistically significant difference between groups.
Question 3: Which study design provides the highest level of evidence for evaluating therapeutic interventions?
- Systematic review with meta-analysis of randomized controlled trials (Correct answer)
- Well-designed cohort study
- Case-control study
- Expert opinion
Correct answer: Systematic review with meta-analysis of randomized controlled trials
Systematic reviews with meta-analyses of RCTs sit at the top of the evidence hierarchy for therapeutic questions.
Question 4: In a crossover trial, which design feature helps control for carryover effects?
- Washout period between treatment phases (Correct answer)
- Randomization of treatment sequence
- Blinding of participants
- Use of placebo in the control arm
Correct answer: Washout period between treatment phases
A washout period allows prior treatment effects to dissipate before the next phase begins, controlling for carryover.
Question 5: A pharmacist reviews a trial where the primary endpoint was changed after enrollment began but before unblinding. This is an example of:
- Outcome reporting bias (Correct answer)
- Allocation concealment failure
- Attrition bias
- Detection bias
Correct answer: Outcome reporting bias
Changing the primary endpoint after trial initiation but before unblinding introduces outcome reporting bias.
Question 6: A study reports a sensitivity of 92% and specificity of 85% for a diagnostic test. Which statement is correct?
- The test correctly identifies 92% of true positive cases (Correct answer)
- The test correctly identifies 92% of true negative cases
- The test has a false positive rate of 92%
- Specificity measures the ability to detect disease
Correct answer: The test correctly identifies 92% of true positive cases
Sensitivity measures the proportion of true positives correctly identified (92% of diseased patients test positive).
Question 7: What does the number needed to harm (NNH) represent?
- The number of patients who must receive a treatment for one additional patient to experience harm (Correct answer)
- The number of harmful events prevented per 100 patients
- The relative increase in adverse events compared to placebo
- The probability of a patient experiencing harm
Correct answer: The number of patients who must receive a treatment for one additional patient to experience harm
NNH = 1/absolute risk increase, representing how many patients need treatment before one additional adverse outcome occurs.
BCACP Clinical Literature Interpretation 3
A cohort study follows patients with and without statin use over 10 years to assess cardiovascular events.
What measure of association is most appropriate to report?