Table 2.

Methodologic quality and risk of bias of the selected studies

Author (year)Random sequence generationAllocation concealmentBlinding of participants and personnelBlinding of outcome assessmentComplete outcome dataSelective reporting (ITT analysis)Other bias
Bower and colleagues (2014)+++++
Rogers and colleagues (2014)+++?++
Ergun and colleagues (2013)+??++?+
Guinan and colleagues (2013)+?+++
Karimi and colleagues (2013)+??+??
Thomas and colleagues (2013)+???++
Jones and colleagues (2012)+??++++
Nuri and colleagues (2012)+??++?+
Rogers and colleagues (2012)+??+++
Sprod and colleagues (2012)++++
Gomez and colleagues (2011)+++++
Irwin and colleagues (2009)+??++++
Ligibel and colleagues (2008, 2009)+??+++
Hutnick and colleagues (2005)+??++
Schmitz and colleagues (2005)+++++++
Fairey and colleagues (2003, 2005)+++++++
  • Abbreviations: +, low risk of bias; −, high risk of bias; ?, unclear risk of bias; ITT, intention-to-treat.