FFICM Research and Development 2 — Questions and Answers
Question 1: In a randomised controlled trial of a new sedation protocol in ICU patients, which statistical test is most appropriate for comparing time to extubation between two groups when the data is not normally distributed?
- Student's t-test
- Mann-Whitney U test (Correct answer)
- Chi-squared test
- Pearson correlation
Correct answer: Mann-Whitney U test
The Mann-Whitney U test is a non-parametric test used to compare two independent groups when data is not normally distributed, making it appropriate for skewed time-to-event data.
Question 2: A systematic review on vasopressor use in septic shock includes studies with significant clinical heterogeneity. Which approach best addresses this in a meta-analysis?
- Use a fixed-effects model only
- Exclude all heterogeneous studies
- Use a random-effects model and report I² statistic (Correct answer)
- Pool all studies regardless of heterogeneity
Correct answer: Use a random-effects model and report I² statistic
A random-effects model accounts for between-study variability, and the I² statistic quantifies the proportion of total variation attributable to heterogeneity.
Question 3: A researcher wants to determine how many patients are needed to detect a 10% absolute reduction in 28-day mortality from 40% to 30% with 80% power and a 5% significance level. Which concept determines this calculation?
- Effect size and variance (Correct answer)
- Confidence interval width
- Number needed to treat
- Likelihood ratio
Correct answer: Effect size and variance
Sample size calculations require the expected effect size (absolute risk reduction) and variance (estimated from baseline event rate) along with desired power and alpha.
Question 4: In an observational ICU study, patients who received early physiotherapy had lower 90-day mortality. However, these patients also had lower APACHE II scores. This is an example of which bias?
- Selection bias
- Confounding by indication (Correct answer)
- Recall bias
- Attrition bias
Correct answer: Confounding by indication
Confounding by indication occurs when the reason a treatment is given (or withheld) is itself associated with the outcome, distorting the apparent treatment effect.
Question 5: Which pharmacokinetic parameter is most relevant when evaluating whether a drug achieves adequate concentrations at the site of infection in critically ill patients with augmented renal clearance?
- Volume of distribution
- Time above MIC (T>MIC) (Correct answer)
- Peak-to-MIC ratio
- Area under the inhibitory curve (AUIC)
Correct answer: Time above MIC (T>MIC)
For time-dependent antibiotics (e.g., beta-lactams), the percentage of time the free drug concentration exceeds the MIC is the primary pharmacodynamic target.
Question 6: A clinical researcher wishes to measure ICU patients' quality of life six months after discharge. Which validated tool is most widely used for this purpose in critical care research?
- APACHE II score
- EQ-5D-5L (Correct answer)
- SOFA score
- Barthel Index
Correct answer: EQ-5D-5L
The EQ-5D-5L is a generic, validated health-related quality of life instrument widely used as a patient-reported outcome measure in ICU survivorship research.
Question 7: In adaptive clinical trial design, what is the primary advantage over a traditional fixed design?
- It eliminates the need for a control group
- It allows pre-specified modifications to the trial based on interim data (Correct answer)
- It removes the requirement for informed consent
- It guarantees a statistically significant result
Correct answer: It allows pre-specified modifications to the trial based on interim data
Adaptive designs allow pre-specified modifications such as sample size re-estimation or arm dropping based on interim analyses, increasing efficiency without inflating type I error.
FFICM Research and Development 2
In a randomised controlled trial of a new sedation protocol in ICU patients, which statistical test is most appropriate for comparing time to extubation between two groups when the data is not normally distributed?