Table 2. A tabulated summary of the Newcastle-Ottawa risk of bias tool.

Newcastle-Ottawa criteria (Yes, No, Uncertain)	Khoja et al. 2017 [17]	Mirhoseini et al. 2018 [18]	Krishnaswamy et al. 2019 [23]	Shamy et al. 2020 [32]	Kaminska et al. 2020 [25]	Fite et al. 2020 [33]
Representative of the exposed cohort	Uncertain	Uncertain	Uncertain	Uncertain	Uncertain	Uncertain
Selection of external control	Uncertain	Uncertain	Uncertain	Uncertain	Uncertain	Uncertain
Ascertainment of exposure	Yes	Yes	Yes	Yes	Yes	Yes
Outcome of interest not present at the start of the study	Yes	Yes	Yes	Yes	Yes	Yes
Comparability of main factor	Yes	Yes	Yes	Yes	Yes	Yes
Comparability of additional factor	Uncertain	Uncertain	Uncertain	Uncertain	Yes	Uncertain
Assessment of outcome	Yes	Yes	Yes	Yes	Yes	Yes
Sufficient follow-up time	Yes	Yes	Yes	Yes	Yes	Yes
Adequacy of follow-up	Yes	Yes	Yes	Yes	Yes	Yes
Our evaluation	6/9 (Medium quality)	6/9 (Medium quality)	6/9 (Medium quality)	6/9 (Medium quality)	7/9 (Medium quality)	6/9 (Medium quality)