Study ID

Randomisation

Alloc. Concealment

Subject Blinding

Observer Blinding

Assessor Blinding

Completeness of F‐up

Levin 1981

B

A

A

A

B

A

Yaqub 1992

B

A

A

A

B

B

Ziegler 1993

B

B

B

B

B

B

Duque 1994

A

A

A

A

D

A

Stracke 1996

B

B

A

A

B

B

Abbas 1997

B

A

A

A

B

A

Woelk 1998

B

B

A

A

B

A

Strokov 1999

B

B

A

B

B

A

WInkler 1999

C

C

D

D

D

B

Hu 2004

C

B

D

B

B

B

Kovrazhkina 2004

B

B

B

B

B

A

Li X 2005

B

B

D

B

B

A

Zhang 2005

B

B

A

B

B

A