TABLE 2.

Assessment of Potential Bias^a

	Bias
Study	Selection	Performance	Detection	Attrition	Reporting	GRADE Quality
Logan26	High	High	Low	Unclear	High	Very low
Brose5	High	High	Low	Unclear	High	Very low
Straub37	Unclear	High	Low	Unclear	High	Very low
Litwhiler25	High	High	Low	Low	Unclear	Very low
DeRenne8	Unclear	High	Low	Low	Unclear	Low
DeRenne7	Unclear	High	Low	Low	Unclear	Low
Szymanski38	Unclear	High	Low	Unclear	High	Very low
Yang46	High	High	Low	Low	Unclear	Low
Morimoto30	Unclear	High	Low	Low	Unclear	Low
Reinold33	Unclear	Unclear	Low	Low	Low	High

^aEach study was assessed for potential bias according to the guidelines in the Cochrane manual.²¹ An evidence grade was assigned according to the GRADE Working Group guidelines.¹