Table 1 Quality assessment of included studies
Author | Year | Region | Study design | Downs and Black quality score | OCEBM levels of evidence | |||||
|---|---|---|---|---|---|---|---|---|---|---|
Reporting (11) | External validity (3) | Internal validity - bias (7) | Internal validity - confounding (6) | Power (5) | Total (32) | |||||
Yoon C.H. et al. | 2016 | Korea | RCT | 9 | 3 | 6 | 6 | 5 | 29 | Level 2 |
Gottenberg J.E. et al. | 2014 | France | RCT | 10 | 3 | 7 | 6 | 5 | 31 | Level 2 |
Fox R.I. et al. | 1996 | USA | Retrospective | 10 | 0 | 3 | 3 | 5 | 21 | Level 4 |
Kruize A.A. et al. | 1993 | Netherlands | Cross-over | 10 | 2 | 7 | 5 | 3 | 27 | Level 2 |