Table 3.

Methodological quality of studies included in the final analysis, based on the Newcastle–Ottawa Scale for assessing the quality of case–control studies.

	Selection (score)				Comparability (score)	Exposure (score)
Study	Adequate definition of patient cases	Representativeness of patient cases	Selection of controls	Definition of controls	Control for important factor or additional factor	Ascertainment of exposure (blinding)	Same method of ascertainment for participants	Non-response rate∗	Total Score†
Hoffman[7]	1	1	0	1	1	0	1	1	6
Kontorovich[8]	1	1	0	1	1	0	1	1	6
Yang[9]	1	1	1	1	2	0	1	1	8
Zhang[10]	1	1	1	1	0	0	1	1	6
Zhang[11]	1	1	1	1	2	0	1	1	8
Catucci[12]	1	1	1	1	1	0	1	1	7
Ma[13]	1	1	0	1	1	0	1	1	6
Zhang[14]	1	1	0	1	2	0	1	1	7
Wang[15]	1	1	0	1	0	0	1	1	5
He[16]	1	1	1	1	1	0	1	1	7
Qi[17]	1	1	1	1	2	0	1	1	8
Zhang[18]	1	1	1	1	0	0	1	1	6
Morales[19]	1	1	1	1	2	0	1	1	8
Nguyen[20]	1	1	0	1	0	0	1	1	5
Shekari[21]	1	1	0	1	0	0	1	1	5
Mashayekhi[22]	1	1	0	1	2	0	1	1	7

^∗One point was awarded when there was no significant difference in the response rate between the two groups based on a chi-squared test (P > .05).

^†Total score was calculated by adding up the points awarded for each item.