Table 2.

Quality assessment of included studies based on the Quality In Prognosis Studies (QUIPS)

Study [Ref.]	Quality evaluation of prognosis study						Total scorea	Level of evidenceb
	Study participation	Study attrition	Prognostic factor measurement	Outcome measurement	Study confounding	Statistical analysis and reporting
Jia 2019 [44]	Yes	Partly	Yes	Yes	Partly	Yes	7	2b
Peng 2018 [18]	Yes	Partly	Yes	Yes	Partly	Yes	7	2b
Liu 2018 [45]	Yes	Partly	Partly	Yes	Partly	Yes	5	2b
Yang 2018 [46]	Yes	Partly	Yes	Yes	Partly	Yes	7	2b
Asukai 2017 [16]	Partly	Partly	Partly	Yes	Partly	Partly	6	2b
Zhou 2017 [47]	Yes	Partly	Yes	Partly	Partly	Partly	7	2b
Chen 2016 [11]	Yes	Partly	Yes	Partly	Partly	Partly	5	2b
Jiang 2016 [17]	Partly	Partly	Partly	Yes	Partly	Partly	5	2b
Yuan 2016 [14]	Yes	Partly	Yes	Yes	Partly	Yes	8	1b
He 2014 [15]	Yes	Yes	Yes	Yes	Partly	Yes	8	1b
Li 2014 [21]	Yes	Yes	Yes	Yes	Partly	Yes	7	2b
Wang 2012 [48]	Partly	Partly	Yes	Yes	Partly	Yes	6	2b
Hashimoto 2019 [49]	Yes	Yes	Yes	Yes	Partly	Yes	8	1b
Ulivi 2019 [50]	Partly	Partly	Yes	Yes	Partly	Yes	6	2b
Hu 2018 [51]	Yes	Yes	Yes	Partly	Partly	Partly	9	2b
Ecke 2017 [52]	Yes	Partly	Yes	Yes	Partly	Yes	7	2b
Li 2017 [22]	Yes	Partly	Yes	Yes	Partly	Yes	7	2b
Chang 2016 [23]	Yes	Yes	Yes	Partly	Partly	Partly	8	2b
Sheng 2015 [24]	Partly	Partly	Yes	Yes	Partly	Yes	7	2b
Kjersem 2014 [30]	Partly	Partly	Yes	Partly	Partly	Partly	6	2b
Wang 2014 [25]	Partly	Partly	Yes	Yes	Partly	Yes	7	2b
Colangelo 2013 [26]	Partly	Partly	Yes	Partly	Partly	Partly	5	2b
Zhao 2013 [31]	Partly	Partly	Yes	Yes	Partly	Yes	6	2b
Nakatani 2012 [53]	Partly	Partly	Partly	Yes	Partly	Yes	5	2b

^aQuality assessment of included studies based on the Newcastle–Ottawa Scale

^bThe levels of evidence were estimated for all included studies with the Oxford Centre for Evidence Based Medicine criteria