Table 4.
Summary of global ratings for study quality.
| Quality Rating | |||
|---|---|---|---|
| Quality Component | Strong (n) | Moderate (n) | Weak (n) |
| Selection bias | 2/13 | 4/13 | 7/13 |
| Study design | 0/13 | 0/13 | 13/13 |
| Confounders | 3/13 | 0/13 | 10/13 |
| Blinding | 0/13 | 2/13 | 11/13 |
| Data collection methods | 13/13 | 0/13 | 0/13 |
| Withdrawal and dropout | 5/13 | 1/13 | 7/13 |
| Global rating | 0/13 | 0/13 | 13/13 |
1: Strong; 2: Moderate; 3: Weak. Global weak quality: two or more weak component ratings; moderate quality: less than four strong and one weak component ratings, high quality: four strong and no weak component ratings.