Pairwise meta-analysis of aggregate data using metaan in Stata

A few years ago, we developed metaan, a package to perform fixed- or random-effects meta-analysis. In terms of random-effects meta-analysis, it of- fered a wide choice of models, including maximum likelihood, profile likelihood, or restricted maximum-likelihood, in addition to the established DerSimonian–Laird method available in metan or Cochrane’s RevMan software. Other unique features included a wide range of reported heterogeneity measures and a plot of the max- imum likelihood function. Since then, metaan has been continuously updated to offer improved graphics, more options, and more meta-analysis models. In this necessary update, we describe these additions and discuss the new models and the evidence behind them.