Summary of modified QI checklist scores (n=22)
| Study | Reporting (x/11) | External validity (x/3) | Internal validity-bias (x/7) | Internal validity-confounding (x/6) | Power (x/1) | Total score (x/28) | Quality rating* |
| An et al 201529 | 10 | 0 | 4 | 2 | 0 | 16 | Fair |
| Buckeridge et al 201213 | 10 | 0 | 4 | 2 | 1 | 21 | Good |
| Fletcher et al 201538 | 9 | 1 | 4 | 2 | 0 | 16 | Fair |
| Gill et al 201237 | 10 | 2 | 4 | 3 | 0 | 19 | Good |
| Holt et al 200316 | 10 | 0 | 4 | 3 | 0 | 17 | Fair |
| Klein et al 199140 | 10 | 0 | 4 | 3 | 0 | 17 | Fair |
| MacManus et al 201328 | 10 | 0 | 4 | 2 | 0 | 16 | Fair |
| Martinez-valdes et al 201912 | 10 | 0 | 4 | 1 | 0 | 15 | Fair |
| McGregor et al 2002a35 | 9 | 0 | 4 | 2 | 1 | 16 | Fair |
| McGregor et al 2002b41 | 9 | 0 | 4 | 2 | 0 | 15 | Fair |
| McGregor et al 2004a42 | 9 | 0 | 4 | 2 | 0 | 15 | Fair |
| McGregor et al 2004b27 | 10 | 0 | 4 | 3 | 0 | 15 | Fair |
| McGregor et al 200526 | 9 | 1 | 4 | 3 | 0 | 17 | Fair |
| McGregor et al 200725 | 10 | 1 | 4 | 3 | 0 | 18 | Fair |
| Nowicky et al 200536 | 10 | 1 | 4 | 3 | 0 | 18 | Fair |
| Parkin et al 200114 | 11 | 0 | 4 | 2 | 0 | 17 | Fair |
| Pollock et al 200939 | 11 | 0 | 4 | 3 | 0 | 18 | Fair |
| Roy et al 199043 | 9 | 0 | 4 | 3 | 0 | 16 | Fair |
| Steer et al 200622 | 10 | 0 | 4 | 3 | 0 | 17 | Fair |
| Strahan et al 201121 | 10 | 0 | 4 | 1 | 0 | 15 | Fair |
| Wilson et al 201219 | 10 | 0 | 4 | 3 | 0 | 17 | Fair |
| Wilson et al 201315 | 10 | 1 | 4 | 2 | 0 | 17 | Fair |
*Quality rating of ‘excellent’ (24–28 points), ‘good’ (19–23 points), ‘fair’ (14–18 points) or ‘poor’ (<14 points).32