Table 3.

Assessment of risk of bias using the ‘Quality Assessment in Prognostic Studies’ (QUIPS) tool

Author	Study participation	Study attrition	Prognostic factor measurement	Outcome measurement	Study confounding	Statistical analysis and reporting	Overall
Courtney et al. 2018 [26]	Moderate	Low	Moderate	Low	High	Moderate	Moderate
Mancini et al. 2018 [27]	Low	Low	Low	Low	Moderate	Low	Low
Jambhekar et al. 2018 [28]	Low	Moderate	Moderate	Moderate	Moderate	Low	Moderate
Keith et al. 2018 [29]	Low	Moderate	Moderate	Moderate	Moderate	Low	Moderate
Hanvold et al. 2015 [30]	Low	Low	Low	Low	Moderate	Low	Low
Reid et al. 2018 [31]	Low	Low	Low	Low	Low	Low	Low
Velcu et al. 2005 [32]	Low	Low	Low	Low	Moderate	Low	Low
Diaz- Guerra et al. 2005 [33]	Moderate	Low	Moderate	Low	Moderate	Moderate	Moderate

Low low risk of bias, Moderate moderate risk of bias, High high risk of bias

Level of risk of bias was determined by judgment of the prompting items belonging to each assessed domain