Table 2.

Risk of bias assessment cluster RCTs Cluster RCTs.

	Selection bias: allocation concealment	Performance bias: blinding of participants and personnel	Detection bias: blinding of outcome assessment	Attrition bias: incomplete outcome data	Reporting bias: selective reporting
Zaman et al. (22)
Bassichetto and Réa (13)
Moore et al. (14)
Pelto et al. (19)
Santos et al. (15)
Penny et al. (23)

+ Indicates low risk of bias, − indicates high risk of bias, and ? indicate unclear risk of bias.