CSC Research & Evidence-Based Practice 4 — Questions and Answers
Question 1: A trial comparing CABG versus PCI in multivessel CAD uses an intention-to-treat (ITT) analysis. What is the primary advantage of ITT?
- It increases statistical power by excluding non-compliant patients
- It preserves the benefits of randomization and minimizes bias (Correct answer)
- It focuses only on patients who completed the assigned treatment
- It removes crossover patients to improve internal validity
Correct answer: It preserves the benefits of randomization and minimizes bias
ITT analysis analyzes patients in their originally assigned groups regardless of protocol deviations, preserving randomization balance and reducing bias.
Question 2: A new cardiac biomarker has a likelihood ratio positive (LR+) of 12. How does this affect post-test probability compared to a LR+ of 2?
- LR+ of 12 provides a larger increase in post-test probability (Correct answer)
- LR+ of 2 provides a larger increase in post-test probability
- Both LRs increase post-test probability equally
- LR+ values above 5 are clinically uninformative
Correct answer: LR+ of 12 provides a larger increase in post-test probability
Higher LR+ values produce greater increases in post-test probability; LR+ ≥ 10 is considered strong evidence for ruling in a diagnosis.
Question 3: During appraisal of a cardiac surgery RCT, you note the allocation concealment was inadequate. What type of bias does this risk?
- Attrition bias
- Detection bias
- Selection bias (Correct answer)
- Reporting bias
Correct answer: Selection bias
Inadequate allocation concealment allows clinicians to predict and potentially influence group assignments, introducing selection bias.
Question 4: Which statistical test is most appropriate to compare 30-day mortality rates between two cardiac surgical techniques when the outcome is binary?
- Student's t-test
- Analysis of variance (ANOVA)
- Chi-square test or Fisher's exact test (Correct answer)
- Pearson correlation coefficient
Correct answer: Chi-square test or Fisher's exact test
Chi-square or Fisher's exact test compares proportions (binary outcomes) between two independent groups.
Question 5: A cardiology department implements a practice change based on a Cochrane systematic review. Six months later, outcomes are audited. Which EBP step does this audit represent?
- Ask
- Acquire
- Appraise
- Evaluate (Correct answer)
Correct answer: Evaluate
The 5th A in EBP (Evaluate) involves auditing the outcomes of the practice change to determine whether it improved patient care.
Question 6: A study of ICD implantation uses propensity score matching to reduce confounding. What is the primary purpose of this technique?
- To increase sample size by including more patients
- To balance baseline characteristics between treated and untreated groups (Correct answer)
- To eliminate the need for multivariable regression
- To randomize patients retrospectively
Correct answer: To balance baseline characteristics between treated and untreated groups
Propensity score matching balances observed covariates between groups in observational studies to reduce confounding, mimicking randomization.
Question 7: A cardiologist encounters conflicting evidence: a large RCT supports early invasive strategy in NSTEMI, but a recent meta-analysis is inconclusive. According to evidence hierarchy, which source generally carries more weight?
- The meta-analysis, as it synthesizes multiple studies
- The large RCT, as individual trials are always superior
- The meta-analysis when it includes the large RCT in its analysis (Correct answer)
- Neither; expert opinion should supersede both
Correct answer: The meta-analysis when it includes the large RCT in its analysis
A well-conducted meta-analysis that includes the large RCT in its synthesis generally carries the highest level of evidence according to standard hierarchies.
CSC Research & Evidence-Based Practice 4
A trial comparing CABG versus PCI in multivessel CAD uses an intention-to-treat (ITT) analysis.
What is the primary advantage of ITT?