Table 3.

NOS score in a case-control study.

Study	Selection				Comparability	Exposure			Total quality score
	Adequacy of case definition	Representativeness of the cases	Selection of Controls	Definition of Controls	Comparability of cases and controls on the basis of the design or analysis	Ascertainment of exposure	Same method of ascertainment for cases and controls	Non- Response Rate
Chiokadze M et al. (21)	⋆	⋆	–	⋆	⋆	⋆	–	–	5
Barath SH et al. (2019) (17)	–	–	⋆	⋆	⋆	⋆	⋆	–	5

The stars are the symbols commonly used in the evaluation of NOS scale.