Table 2 Study quality
Case–control study | Selection | Comparability | Exposure | Total quality score | |||||
|---|---|---|---|---|---|---|---|---|---|
Adequate definition of cases | Representativeness of cases | Selection of controls | Definition of controls | Control for important factors or additional factors | Ascertainment of exposure (blinding) | Same method of ascertainment for subjects | Non-response rate | ||
Wu [14] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Backes [22] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 7 |
Ding [16] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Hao [17] | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 6 |
Court-Brown [21] | 0 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 5 |
Koski [18] | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 7 |
Al-Mudhaffar [19] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Folk [20] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Cohort study | Selection | Comparability | Outcome | Total quality score | |||||
Representativeness of the exposed cohort | Selection of the non-exposed cohort | Ascertainment of exposure | Demonstration that outcome of interest was not present at start of study | Control for important factors or additional factors | Assessment of outcome | Follow-up was long enough for outcomes to occur | Adequacy of follow up of cohorts | ||
Soni [15] | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 7 |
Assous [23] | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 7 |