Table 2: Newcastle-Ottawa quality assessment scale.

No Reference Case-cohort Representative Selection of Non-exposed Control Ascertainment of Exposure Outcome Negative at Start Comparability by Design Comparability by Analysis Outcome Assessment Duration of Follow-up Score
1 Dursun et al * * * * * * * * 8
2 Porwal et al ** * * * * * * * 9
3 Rahiminejad
et al
* * * * * * * * 8
4 Nair et al x * * * * * * * 7

*indicates that the feature is present; x, that the feature is absent. But for comparability by design this checklist awards maximum of two stars (**), one (*) or none if the feature is completely absent