*2.3. Study Quality Assessment*

The risk of bias of included studies was assessed by one author (F.F.) using the QUADAS-2 method [15]. Briefly, for each study, an evaluation of the seven QUADAS-2 items was performed and each point was scored as having high, low or unclear risk of bias. High and unclear risk of bias were assigned 1 and 0.5 points, respectively; studies that totalled four or more points were excluded from the meta-analysis.
