Study

Study Design

Selection

Comparability

Exposure

Quality Assessment

Zhang et al. [17]

Prospective controlled study

4

2

2

8

Wang et al. [18]

Prospective controlled study

4

2

2

8

Zhang et al. [16]

Prospective controlled study

3

2

2

7

Wang et al. [15]

Retrospective

study

3

2

2

6

Wang et al. [14]

Prospective controlled study

4

2

2

8