[24]

[6]

[25]

[26]

[29]

[27]

[5]

[28]

1

Selection Bias

1

1

3

2

1

1

3

2

2

Study Design

3

1

3

3

1

3

3

3

3

Control for Confounders

3

2

1

1

1

3

3

3

4

Blinding

3

1

3

2

1

3

3

3

5

Data Collection Methods

2

1

1

2

1

2

1

1

6

Withdrawals and Drop-Outs

2

1

3

1

1

2

2

1