Table 2.

Quality assessment of studies included through the Newcasttle-Ottawa scale (NOS).

Study	Representative sample	Size of the sample	Course of the information	Outcome not presented at the beginning of the study	Control of the confusion variable	Evaluation of the outcome	Period of monitoring	Total scale score Newcasttle Ottawa
Chen et al 2020	★		★	★	★	★		5/7
Grasselli et al 2020	★	★	★	★	★	★	★	7/7
Guan et al 2020	★		★	★	★	★		5/7
Wang et al 2020	★		★	★	★	★	★	6/7
	★		★	★	★	★	★	6/7
Zhao et al 2020	★		★	★	★	★		5/7
Zhou et al 2020	★		★	★	★	★	★	6/7