Table 4.

Overview of bias in selection of study population, data quality, and statistical analysis

Study	Year	Selection bias		Risk of donation	Information bias		Risk of donation	Confounding	Risk of donation
		Donors	Non-donors		Donors	Non-donors
Mjoen et al. [11]	2012	−	+	Underestimation	+	−	Overestimation	−	n/a
Mjoen et al. [8]	2014	+	+	Overestimation	+	+	Overestimation	+	Overestimation
Segev et al. [12]	2010	−	+	Unclear	+	+	Overestimation	−	n/a
Muzaale et al. [9]	2014	−	+	Overestimation	+	+	Overestimation	+	Overestimation
Garg et al. [13]	2012	−	+	Underestimation	+	−	Overestimation	−	n/a
Garg et al. [10]	2015	−	+	No effect	+	−	Overestimation	−	n/a

+ or – bias present/not present in study