Table 2.

Internal validity of included studies

Study	Prospective design	Multicenter enrollment	Selection bias	Performance bias	Attrition bias	Detection bias	Multivariate adjustment for potential confounders
Schiess 2021 [102]	Yes	No	D	B	A	D	Probably adequate
Venkataramana 2012 [103]	Yes	No	D	B	C	A	Probably adequate
Boika 2020 [104]	Yes	No	D	B	A	D	Probably adequate
Storch 2012 [105]	No	Yes	D	D	C	D	Not reported
Brazzini 2010 [106]	No	No	D	B	A	C	Not reported
Madrazo 2019 [107]	Yes	No	D	B	A	D	Probably adequate
Lige 2016 [108]	Yes	No	D	B	A	D	Not reported
Sinelnyk 2015 [109]	Yes	No	D	B	A	D	Probably adequate
Yin 2012 [110]	Yes	No	D	B	A	A	Probably adequate
Gross 2011 [111]	Yes	Yes	A	A	A	A	Probably adequate
Stover 2005 [112]	Yes	No	D	B	A	D	Probably adequate

Risk of bias is expressed as A = low, B = moderate, C = high, or D = incomplete reporting