General Surgery Board Review Research & Evidence-Based Practice 5 — Questions and Answers
Question 1: Which statistical test is most appropriate to compare complication rates (dichotomous outcome) between two independent surgical groups?
- Paired t-test
- Mann-Whitney U test
- Chi-square test (Correct answer)
- Pearson correlation
Correct answer: Chi-square test
The chi-square test compares proportions of categorical (dichotomous) outcomes between two independent groups.
Question 2: The 'learning curve' phenomenon in surgical research is best addressed methodologically by:
- Excluding early cases from outcome analysis
- Reporting outcomes stratified by surgeon experience or case sequence (Correct answer)
- Using only expert surgeons to perform all study procedures
- Increasing the follow-up period to allow outcomes to stabilize
Correct answer: Reporting outcomes stratified by surgeon experience or case sequence
Stratifying outcomes by case sequence or surgeon experience transparently accounts for the learning curve rather than hiding it.
Question 3: A researcher reports a hazard ratio (HR) of 0.65 (95% CI: 0.48–0.88) for mortality after a new surgical technique. This means:
- The new technique increases mortality by 35%
- Patients receiving the new technique have a 35% lower hazard of death at any given time point (Correct answer)
- The result is not statistically significant
- The survival advantage is observed only at 5 years
Correct answer: Patients receiving the new technique have a 35% lower hazard of death at any given time point
HR < 1 favors the treatment group; HR 0.65 means a 35% reduction in the instantaneous risk of death compared to control.
Question 4: Regression to the mean is most likely to confound results in a study that:
- Randomizes patients before baseline measurement
- Enrolls patients based on extreme baseline values without a control group (Correct answer)
- Uses blinded outcome assessors
- Stratifies randomization by disease severity
Correct answer: Enrolls patients based on extreme baseline values without a control group
Regression to the mean causes extreme initial values to move toward average on remeasurement; without a control group this can mimic a treatment effect.
Question 5: The CONSORT statement is primarily used to guide:
- Systematic review methodology
- Reporting of randomized controlled trials (Correct answer)
- Design of observational surgical studies
- Statistical analysis of survival data
Correct answer: Reporting of randomized controlled trials
CONSORT (Consolidated Standards of Reporting Trials) is a checklist that standardizes the reporting of RCTs to improve transparency and completeness.
Question 6: Which of the following scenarios best illustrates confounding in a surgical outcomes study?
- A surgeon is unaware of which patients received the experimental treatment
- Older patients in the laparoscopic group have higher mortality, but older age also predicts mortality independently (Correct answer)
- Patients lost to follow-up have worse baseline disease than completers
- The outcome assessor applies different criteria in different hospitals
Correct answer: Older patients in the laparoscopic group have higher mortality, but older age also predicts mortality independently
Confounding occurs when a third variable (age) is associated with both the exposure (surgical approach) and the outcome (mortality), distorting the true relationship.
Question 7: In a cost-effectiveness analysis comparing two hernia repair techniques, an incremental cost-effectiveness ratio (ICER) below the willingness-to-pay threshold implies:
- The new technique costs less and produces fewer QALYs
- The new technique is considered cost-effective relative to the comparator (Correct answer)
- The study should be repeated with a longer time horizon
- The new technique is dominated and should not be adopted
Correct answer: The new technique is considered cost-effective relative to the comparator
An ICER below the willingness-to-pay threshold means society considers the extra cost per QALY gained acceptable, making the intervention cost-effective.
General Surgery Board Review Research & Evidence-Based Practice 5
Which statistical test is most appropriate to compare complication rates (dichotomous outcome) between two independent surgical groups?