Accuracy of Fed-GLMM and meta-analysis estimates relative to the gold-standard pooled analysis.

We compared the accuracy of Fed-GLMM with the standard meta-analysis by calculating the median absolute relative difference compared to the gold-standard pooled estimate of the coefficient of a binary exposure variable. The underlying model has a binary outcome, a binary exposure, three more covariates with 8 site-specific fixed effect coefficients for the normally distributed covariate and a patient-level random intercept. The model also includes 8 site-specific parameters for variance components. We considered 25 combinations of outcome and exposure prevalence to assess the model accuracy with 100 simulation replicates per combination. Fed-GLMM demonstrated reduced relative bias after 1–2 iterations compared with the meta-analysis, which was highly biased in the presence of rare events.