The decomposition of the Q statistics as well as the degrees of freedom of the corresponding chi-squared distributions and the p values are shown. In addition the considered number of studies are displayed. Only one study is observed for the following designs: plac:acar, plac:piog, plac:sita, plac:vild, acar:SUal, metf:piog, metf:SUal, piog:rosi, rosi:SUal, plac:acar:metf. For this reason, the corresponding statistics are not shown.

Krahn * et al.*

Krahn * et al.* *BMC Medical Research Methodology* 2013 **13**:35 doi:10.1186/1471-2288-13-35