Table 2.
Risk of bias and level of evidence of each included study.
| Study | Domains | Overall Appraisal | LOE | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |||
| Plaza-Ruiz et al. [3] | Y | Y | Y | Y | Y | Y | Y | Y | Include | 3 |
| Abbas et al. [7] | Y | Y | Y | Y | Y | Y | Y | Y | Include | 3 |
| Subhan et al. [4] | Y | Y | Y | Y | Y | N | Y | Y | Include | 3 |
| Zahra et al. [15] | Y | Y | Y | Y | Y | Y | Y | Y | Include | 3 |
| AlAssad et al. [8] | Y | Y | Y | Y | Y | Y | Y | Y | Include | 3 |
| Save et al. [16] | Y | Y | Y | Y | Y | Y | Y | Y | Include | 3 |
Y: Yes; U: Unclear; N: No; LOE: Level of evidence. Domain 1: Were the criteria for inclusion in the sample clearly defined? Domain 2: Were the study subjects and the setting described in detail? Domain 3: Was the exposure measured in a valid and reliable way? Domain 4: Were objective, standard criteria used for measurement of the condition? Domain 5: Were confounding factors identified? Domain 6: Were strategies to deal with confounding factors stated? Domain 7: Were the outcomes measured in a valid and reliable way? Domain 8: Was appropriate statistical analysis used?