Table 2.
Risk of bias assessment for observational studies (NOS adapted version).
| Study | Selection Bias | Performance Bias | Detection Bias | Information Bias | Total Score | |||
|---|---|---|---|---|---|---|---|---|
| A | B | C | D | E | F | G | ||
| Tada et al. [30] | 3 | 2 | 0 | 3 | 3 | 3 | 3 | 17 |
| Kadota et al. [31] | 3 | 1 | 1 | 3 | 3 | 2 | 3 | 16 |
| Kubota et al. [34] | 2 | 1 | 2 | 2 | 3 | 2 | 3 | 15 |
| Kubota et al. [36] | 2 | 1 | 2 | 2 | 3 | 2 | 3 | 15 |
| Bibbo et al. [37] | 1 | 2 | 0 | 0 | 3 | 1 | 2 | 9 |
Note: A = Is the source population appropriate and representative of the population of interest?; B = Is the sample size adequate, and is there sufficient power to detect a meaningful difference in the outcome of interest?; C = Did the study identify and adjust for any variables or confounders that may influence the outcome?; D = Did the study use appropriate statistical analysis methods relative to the outcome of interest?; E = Is there little missing data, and did the study handle it accordingly?; F = Is the methodology of the outcome measurement explicitly stated, and is it appropriate?; G = Is there an objective assessment of the outcome of interest?