1. Quantitative Synthesis IIInteractive Quiz Prepared for: The Agency for Healthcare Research and Quality (AHRQ) Training Modules for Systematic Reviews Methods Guide www.ahrq.gov

2. Covariates Assume that you are performing a meta-analysis of randomized controlled trials on vitamin D supplementation and mortality in elderly people who are institutionalized. You want to explore whether or not the treatment effect differs across trials according to their maximum followup. The maximum length of followup is: • A patient-level covariate • A study-level covariate

3. Subgroup Analysis You should perform only the subgroup analyses that are specified a priori and not perform post-hoc subgroup analyses. • False • True

4. Meta-Regressions andthe Risk of Ecological Fallacy Because of the risk of ecological fallacy, meta-regressions on patient-level covariates should never be performed. • True • False

5. Assessing Study Conclusions Based on this example, which of the following statements is more likely to be true? • These conclusions are based on a well constructed meta-regression (see on the right) and are definitely valid. • The analyses and conclusions are suspect. Mean 25-hydroxy-D Concentration

6. Summary • Meta-analyses require understanding of covariates and how to analyze them. • Patient-level covariates differ across patients in the same study or in the same study arm. • Study-level covariates pertain to the whole study and do not vary across patients in the same study. • Results of subgroup analyses should be viewed with skepticism, especially when adjustments for multiple testing have not been performed. • If an association from a meta-regression on the mean of a patient-level covariate is biologically plausible, it merits further study.

7. Authors • This quiz was prepared by Joseph Lau, M.D., and Thomas Trikalinos, M.D., Ph.D., members of the Tufts Medical Center Evidence-based Practice Center. • The information in this module is based on Chapter 9 in Version 1.0 of the Methods Guide for Comparative Effectiveness Reviews (available at: http://www.effectivehealthcare.ahrq.gov/repFiles/2007_10DraftMethodsGuide.pdf).