Table 3.

Results of bias risk assessment

Study	Study population	Predictive variables	Outcomes	Analysis methods	Overall bias risk	Overall applicability
Ruan ZB et al. [13]	+	+	?	?	?	?
Budzianowski J et al. [14]	+	+	+	-	-	+
Zheng D et al. [15]	+	?	+	+	?	?
Zhao Z et al. [16]	?	+	+	-	-	?
Zhou XJ et al. [17]	?	+	+	?	+	?
Liu M et al. [18]	?	+	?	+	?	?
Dong Y et al. [19]	+	+	+	+	+	+
Jia S et al. [20]	?	+	+	-	-	?
Lee DI et al. [21]	?	+	+	?	?	?
Baalman SWE et al. [22]	+	+	+	+	+	+
Saglietto A et al. [23]	+	+	+	+	+	+
Sun S et al. [24]	?	+	+	?	?	?
Yang Z et al. [25]	?	+	?	?	?	?
Sheng J et al. [26]	?	+	?	-	-	?
Ma XX et al. [27]	?	+	?	?	?	?
Tang S et al. [28]	?	+	+	+	?	?
Ma Y et al. [29]	?	+	+	+	?	?

Notes: +: Low risk; -: High risk; ?: Unknown Risks.