Table II.

Assessment of the risk of bias among the eight randomized controlled trials.

First author, year	Random sequence generation (selection bias)	Allocation concealment (selection bias)	Blinding of participants and personnel (performance bias)	Blinding of outcome assessment (detection bias)	Incomplete outcome data (attrition bias)	Selective reporting (reporting bias)	Other sources of bias (other bias)	(Refs.)
Alper et al, 1986	Low risk	Unclear	Unclear	Low risk	High risk	Unclear	Unclear	(14)
de Boer et al, 1988	Unclear	Unclear	Unclear	Low risk	Low risk	Unclear	Low risk	(15)
Rasmussen et al, 1991	Unclear	Unclear	Unclear	Low risk	Unclear	Unclear	Unclear	(16)
Lindequist et al, 1994	Unclear	Unclear	Unclear	Low risk	Unclear	Unclear	Low risk	(17)
Spring et al, 2000	Low risk	Unclear	Unclear	Low risk	Low risk	Low risk	High risk	(18)
Steiner et al, 2003	Low risk	High risk	Unclear	Low risk	Low risk	Unclear	Low risk	(19)
Dreyer et al, 2017	Low risk	Low risk	Unclear	Low risk	Low risk	Low risk	Low risk	(21)
Zhang et al, 2022	Low risk	Unclear	Unclear	Low risk	Low risk	Unclear	Low risk	(23)