Modified Downs and Black scale25
| Paper | Prospective (P) or retrospective (R) study | (1) Clear aim/hypothesis | (2) Outcome measures clearly described | (3) Patient characteristics clearly described | (5) Confounding variables described | (6) Main findings clearly described | (7) Measures of random variability provided | (10) Actual probability values reported | (11) Participants asked to participate representative of entire population | (12) Participants prepared to participate representative of entire population | (15) Blinding of outcome measurer | (16) Analysis completed was planned | (18) Appropriate statistics | (20) Valid and reliable outcome measures | (21) Appropriate case–control matching | (25) Adjustment made for confounding variables | Total |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cowan et al32 | R | 1 | 1 | 1 | 2 | 1 | 1 | 1 | U | U | 1 | 1 | 1 | 1 | 1 | 1 | 14 |
| Earl et al33 | R | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 1 | U | 0 | 1 | 1 | U | 1 | 1 | 12 |
| Boling et al34 | R | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 0 | U | 0 | 1 | 1 | U | 1 | 1 | 12 |
| Aminaka et al36 | R | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | U | 0 | 1 | 1 | U | 1 | 1 | 11 |
| Souza and Powers35 | R | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 0 | U | 0 | 1 | 1 | U | 1 | 1 | 11 |
| Willson et al31 | R | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | U | 0 | 1 | 1 | 1 | 1 | U | 11 |
| Nakagawa et al38 | R | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | U | 0 | 1 | 1 | U | 0 | 0 | 9 |
| Brindle et al39 | R | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | U | 0 | 1 | 1 | U | 0 | U | 8 |
| Ott et al40 | R | 1 | 1 | 0 | 1 | 0 | 1 | 1 | U | U | 0 | 0 | 1 | U | U | U | 6 |
| Saad et al37 | R | 1 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | U | 0 | 1 | 1 | U | 0 | 0 | 5 |
(For items 1–3, 6, 7, 10–12, 15, 16, 18, 20, 21 and 25)—0, no; 1, yes; U, unable to determine. (For item 5)—0, no: 1; partially: 2, yes.