Table 2 Quality assessment score of the included studies

A clearly stated aim

2

2

2

2

2

2

Inclusion of consecutive patients

2

2

2

1

1

1

Prospective data collection

0

0

1

0

2

2

End points appropriate to the aim of the study

2

0

2

2

2

2

Unbiased assessment of the study end point

0

0

0

0

0

0

A follow-up period appropriate to the aims of the study

2

2

2

2

2

2

Less than 5 % loss to follow-up

0

2

2

2

2

2

Prospective calculation of the sample size

0

0

0

0

0

0

An adequate control group

2

2

2

2

2

2

Contemporary groups

2

2

2

2

2

2

Baseline equivalence of groups

2

1

1

2

2

2

Adequate statistical analyses

2

0

2

2

2

2