Risk of bias

We assessed the risk of bias in the studies included in the database by administering two scales: the Cochrane risk of bias tool, and the Jadad scale.

The Cochrane collaboration instrument ascertains the risk of bias based on description and suitability in seven domains: sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective outcome reporting and other sources of bias. Some domains are assessed at study-level (sequence generation, allocation concealment, selective outcome reporting and other sources of bias) and the remaining ones at outcome-level (blinding, incomplete outcome data). This tool involves assigning a judgement relating to the risk of bias for each entry in terms of ‘low’, ‘high’ or ‘unclear’ risk.

The Jadad scale assesses the reporting quality of randomized RCCT. It is based on the description of withdrawals and the description and appropriateness of randomization and double-blinding. Scores range from 0 to 5, and a score below 3 denotes poor study quality