Table 2 Instructions on downgrading for Risk of Bias

No

There are multiple studies of at least adequate quality, or there is one study of very good quality available

Serious

There are multiple studies of doubtful quality available, or there is only one study of adequate quality

Very serious

There are multiple studies of inadequate quality, or there is only one study of doubtful quality available

Extremely serious

There is only one study of inadequate quality available