Table 1

Quantitative studies. Quality assessed using the Standard Quality Assessment Criteria for Evaluating Primary Research Papers from a variety of fields

Authors	Question/objective sufficiently described?	Study design evident and appropriate?	Method of subject/comparison group selection or source of information/input variables described and appropriate?	Subject (and comparison group, if applicable) characteristics sufficiently described?	If interventional and random allocation was possible, was it described?	If interventional and blinding of investigators was possible, was it reported?	If interventional and blinding of subjects was possible, was it reported?	Outcome and (if applicable) exposure measure(s) well defined and robust to measurement/misclassification bias? Means of assessment reported?	Sample size appropriate?	Analytical methods described/justified and appropriate?	Some estimate of variance is reported for the main results?	Controlled for confounding?	Results reported in sufficient detail?	Conclusions supported by the results?	Summary score
An et al 21	2	2	2	1	N/A	N/A	N/A	2	2	1	1	2	2	2	0.86	Yes	2
Bükki et al 22	2	2	2	2	N/A	N/A	N/A	2	1	2	2	0	2	2	0.86	Partial	1
Davies et al 23	2	2	2	1	N/A	N/A	N/A	2	1	2	2	1	1	2	0.82	No	0
Engelberg et al 24	2	2	2	2	N/A	N/A	N/A	2	1	2	1	1	2	2	0.86	N/A
Gao et al 25	2	2	2	2	N/A	N/A	N/A	2	1	2	1	2	2	2	0.91
Hauke et al 26	2	2	2	2	N/A	N/A	N/A	2	1	1	0	1	2	2	0.77
Heyland et al 27	2	2	2	2	N/A	N/A	N/A	2	2	2	1	1	2	2	0.91
Heyland et al 28	2	2	2	1	N/A	N/A	N/A	2	1	2	2	0	2	0	0.73
Hwang et al 29	1	2	2	2	N/A	N/A	N/A	2	1	2	1	1	2	2	0.82
Kim et al 30	2	2	2	2	N/A	N/A	N/A	2	1	2	2	2	2	0	0.86
Ozdemir et al 31	2	2	2	2	N/A	N/A	N/A	2	1	2	1	2	2	2	0.91
Pruchno et al 32	2	2	1	2	N/A	N/A	N/A	2	1	1	2	2	2	2	0.86
Sharma et al 33	2	2	2	2	N/A	N/A	N/A	2	1	2	1	2	2	2	0.91
Shin et al 34	2	2	2	2	N/A	N/A	N/A	1	2	1	2	2	1	2	0.86
Stajduhar et al 35	2	2	2	2	N/A	N/A	N/A	1	1	2	0	2	2	2	0.82
Tang et al 36	2	2	2	2	N/A	N/A	N/A	2	2	1	2	2	2	2	0.95
Tobin et al 37	2	2	2	2	N/A	N/A	N/A	1	2	2	1	2	2	2	0.91
Wen et al 38	2	2	1	2	N/A	N/A	N/A	2	2	2	1	2	2	2	0.91
Yoo et al 39	2	2	2	2	N/A	N/A	N/A	1	1	1	2	2	2	2	0.86
Yun et al 40	1	2	1	2	N/A	N/A	N/A	2	2	2	2	2	2	2	0.91
Zhang et al 41	2	2	1	2	N/A	N/A	N/A	1	2	2	2	2	2	2	0.91

The summary score for each study is derived by calculating the total score of relevant items (ie, all items except those ‘not applicable’) and dividing it by the total possible score when excluding ‘not applicable’ items.
N/A, not applicable.