Table 2.

Assessment of the quality of the non-radomized controlled trial (RCT) studies using the Newcastle–Ottawa scale for case-control studies.

	Selection				Comparability	Exposure
Reference	CDA	RC	SC	DC	CCC	AE	SMA	NRR	Score
Kondo et al. [24]	☆			☆	☆☆	☆	☆		6
Fajkovic et al. [22]	☆	☆		☆	☆☆	☆	☆		7
Kobayashi et al. [25]	☆	☆		☆	☆☆	☆	☆		7
Chappidi et al. [10]	☆			☆	☆☆	☆	☆		6
Zareba et al. [26]	☆			☆	☆☆	☆	☆		6
Winer et al. [23]	☆			☆	☆☆	☆	☆		6

CDA: case definition adequate; RC: representativeness of the cases; SC: selection of controls; DC: definition of controls; CCC: comparability of cases and controls on the basis of the design or analysis; AE: ascertainment of exposure; SMA: same method of ascertainment for the cases and controls; NRR: non-response rate; A study can be awarded a maximum of one star (☆) for each numbered item within the selection and exposure categories. A maximum of two stars can be given for comparability.