The methodological quality of case–control studies in accordance with the Newcastle-Ottawa Scale (NOS)
| Selection | Comparability | Exposure | Total score | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Study | Is the case definition adequate? | Representativeness of the cases | Selection of controls | Definition of controls | Comparability of cases and controls on the basis of the design or analysis | Ascertainment of exposure | Same method of ascertainment for cases and controls | Non-response rate | |
| Yuan35 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 5 |
| Muckadell32 | 0 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 6 |