Table 2.
Risk of bias in the retrospective study
| Study | Selection | Comparability | Outcome | Quality score | ||||
|---|---|---|---|---|---|---|---|---|
| Representative exposed group | Representative reference group | Assignment for exposed groupa | Comparable for 1, 2, 3, 4b | Comparable for 5, 6, 7, 8b | Assessment of outcome | Adequate follow-up | ||
| Naderi et al33 | Yes | Yes | Yes | 2, 4 | 6, 7 | Yes | Yes | ⋆⋆⋆⋆⋆⋆⋆ |
Notes: Comparability variables: 1=age; 2=gender; 3=FEV1 (%) of predicted; 4=corticosteroids inhalation medication; 5=body mass index; 6=smoking status; 7=any inhalation medication; 8=exacerbation previous year.
a
Details of criteria for adequate random assignment of patients to the exposed group were provided.
b
If all characteristics were comparable, two stars; if two or three characteristics were comparable, one star; otherwise, no star.