3.3 Quality of studies
The risk of bias of included works has been assessed in eight categories
using the ACROBAT-NRSI tool recommended by the Cochrane group and an
over-all score was calculated indicating the quality of each analyzed
study (Table 4). Altogether, eleven studies with a moderate risk, and
two studies were categorized with a serious risk of bias. In particular,
3(23%) and 5 (38%) studies were rated with a high risk of bias in the
categories“ match with prognostic variables” and “Co-intervention
between groups”.