Table 2: Risk of bias of included RCTs*.

Study Random sequence generation Allocation concealment Patient blinding Assessor blinding Reporting drop-out or withdrawal† Intention-to-treat analysis† Selective outcome reporting Other potential bias Wang et al. 2010 [7] Low Low Low Low Low Low Low Low Hsiao et al. 2003 [8] Unclear Low Low Low Low High Low Unclear Özsoy and Ernst 1999 [9] Low Low Low Low Low High Low Low Liu et al. 2005 [10] Low Low Low Low Low High Low Low Bishop et al. 2007 [11] Low Low Low Low Low Low Low Low Tsao et al. 2005 [12] Low Low Low Low Low High Low Low Higgins et al. 2011 [24] Unclear Low Low Low Low Low Low Unclear Burack et al. 1996 [13] Low High High High Low Low Low Unclear Sangkitporn et al. 2005 [14] Low Low Low Low Low Low Low Low Shi and Peng 2003 [15] Low Low Low High Low Low Low Unclear Wang et al. 2006 [16] Low Low Low Low Low Low Low Low

Domains of quality assessment based on Cochrane tools for assessing risk of bias. Two domains referring to “incomplete outcome data” in the Cochrane tools for assessing risk of bias. Abbreviations: low: low risk of bias; high: high risk of bias; unclear: uncertain risk of bias.