CRA Systematic Review & Meta-Analysis 3 — Questions and Answers
Question 1: In meta-analysis, the trim-and-fill method is used to:
- Remove low-quality studies before pooling
- Impute missing effect sizes from unpublished studies to correct for publication bias (Correct answer)
- Trim outlier effect sizes beyond 2 standard deviations
- Fill in missing participant data using multiple imputation
Correct answer: Impute missing effect sizes from unpublished studies to correct for publication bias
The trim-and-fill method estimates and imputes potentially missing studies to produce an adjusted pooled effect corrected for funnel plot asymmetry.
Question 2: A systematic review searching only MEDLINE and PubMed without grey literature is most at risk for which bias?
- Attrition bias
- Language bias
- Publication bias (Correct answer)
- Performance bias
Correct answer: Publication bias
Restricting searches to major indexed databases omits unpublished or informally published studies, which tend to show null results, inflating apparent effect sizes.
Question 3: Which effect size measure is most commonly used to pool continuous outcomes across studies in a meta-analysis?
- Odds ratio
- Number needed to treat
- Standardized mean difference (SMD) (Correct answer)
- Relative risk
Correct answer: Standardized mean difference (SMD)
The SMD (e.g., Cohen's d, Hedges' g) enables pooling of continuous outcomes measured on different scales across studies.
Question 4: GRADE methodology in systematic reviews evaluates certainty of evidence across how many domains that can downgrade quality?
- 3
- 5 (Correct answer)
- 7
- 10
Correct answer: 5
GRADE uses five downgrading domains: risk of bias, inconsistency, indirectness, imprecision, and publication bias.
Question 5: A Galbraith plot in meta-analysis is an alternative diagnostic tool used to visualize:
- Cumulative effect size over time
- Heterogeneity and potential outlier studies (Correct answer)
- Subgroup differences by study design
- Bayesian posterior distributions
Correct answer: Heterogeneity and potential outlier studies
The Galbraith (radial) plot plots standardized effect estimates against their precision, helping identify studies contributing to heterogeneity.
Question 6: When conducting a meta-analysis of diagnostic test accuracy, which pair of statistics is typically pooled?
- Mean difference and relative risk
- Sensitivity and specificity (Correct answer)
- Hazard ratio and number needed to treat
- Cohen's d and Pearson's r
Correct answer: Sensitivity and specificity
Sensitivity (true positive rate) and specificity (true negative rate) are the primary metrics pooled in diagnostic meta-analyses using bivariate models.
Question 7: Which component of the PICO framework specifies the alternative against which an intervention is evaluated?
- Population
- Intervention
- Comparison (Correct answer)
- Outcome
Correct answer: Comparison
The Comparison element defines the control or alternative treatment (e.g., placebo, standard of care) against which the intervention is contrasted.
CRA Systematic Review & Meta-Analysis 3
In meta-analysis, the trim-and-fill method is used to: