title: Metaprop: a Stata command to perform meta-analysis of binomial data.
abstract: BACKGROUND
  Meta-analyses have become an essential tool in synthesizing evidence on clinical and epidemiological questions derived from a multitude of similar studies assessing the particular issue. Appropriate and accessible statistical software is needed to produce the summary statistic of interest.
  
  
  METHODS
  Metaprop is a statistical program implemented to perform meta-analyses of proportions in Stata. It builds further on the existing Stata procedure metan which is typically used to pool effects (risk ratios, odds ratios, differences of risks or means) but which is also used to pool proportions. Metaprop implements procedures which are specific to binomial data and allows computation of exact binomial and score test-based confidence intervals. It provides appropriate methods for dealing with proportions close to or at the margins where the normal approximation procedures often break down, by use of the binomial distribution to model the within-study variability or by allowing Freeman-Tukey double arcsine transformation to stabilize the variances. Metaprop was applied on two published meta-analyses: 1) prevalence of HPV-infection in women with a Pap smear showing ASC-US; 2) cure rate after treatment for cervical precancer using cold coagulation.
  
  
  RESULTS
  The first meta-analysis showed a pooled HPV-prevalence of 43% (95% CI: 38%-48%). In the second meta-analysis, the pooled percentage of cured women was 94% (95% CI: 86%-97%).
  
  
  CONCLUSIONS
  By using metaprop, no studies with 0% or 100% proportions were excluded from the meta-analysis. Furthermore, study specific and pooled confidence intervals always were within admissible values, contrary to the original publication, where metan was used.
authors: Unit of Cancer Epidemiology, Scientific Institute of Public Health, Juliette Wytsmanstraat 14, 1050 Brussels, Belgium.
authors: Victoria N
authors: VN
authors: Nyaga
authors: Unit of Cancer Epidemiology, Scientific Institute of Public Health, Juliette Wytsmanstraat 14, 1050 Brussels, Belgium.
authors: Marc
authors: M
authors: Arbyn
authors: Center for Statistics, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium.
authors: Marc
authors: M
authors: Aerts
keywords: Binomial; Confidence intervals; Freeman-Tukey double arcsine transformation; Logistic-normal; Meta-analysis; Stata