Table 2.
Methodologic quality of included studies with the NOS.
| Study (authors-year) | Representativeness of the exposed cohort | Selection of the nonexposed cohort | Ascertainment of exposure | Demonstration that outcome of interest was not present at the start of the study | Comparability of cohorts on the basis of the design or analysis | Assessment of outcome | Was it followed up long enough for outcomes to occur? | Adequacy of follow-up of cohorts | Total score |
|---|---|---|---|---|---|---|---|---|---|
| Pretreatment | |||||||||
| Song BG (2018) | ★ | ★ | ★ | — | ★★ | ★ | ★ | ★ | 8 |
| Paik N (2018) | ★ | ★ | ★ | — | ★★ | ★ | ★ | ★ | 8 |
| Chang KC (2018) | ★ | ★ | ★ | — | ★★ | ★ | ★ | ★ | 8 |
| Kim JH (2018) | ★ | ★ | ★ | — | ★ | ★ | ★ | ★ | 7 |
| Nishikawa H (2017) | ★ | ★ | ★ | — | ★★ | ★ | ★ | ★ | 8 |
| Ji FP (2017) | ★ | ★ | ★ | — | — | ★ | ★ | ★ | 6 |
| Kim JH (2016) | ★ | ★ | ★ | — | — | ★ | ★ | ★ | 6 |
| Lee K (2016) | ★ | ★ | ★ | — | — | ★ | ★ | ★ | 6 |
| Wu CK (2016) | ★ | ★ | ★ | — | — | ★ | ★ | ★ | 6 |
| Ng KJ (2016) | ★ | ★ | ★ | — | ★ | ★ | ★ | ★ | 7 |
| Hann HW (2015) | ★ | ★ | ★ | — | ★★ | ★ | ★ | ★ | 8 |
| Posttreatment | |||||||||
| Ji FP (2017) | ★ | ★ | ★ | — | — | ★ | ★ | ★ | 6 |
| Wu CK (2016) | ★ | ★ | ★ | — | ★★ | ★ | ★ | ★ | 8 |
| Chen TM (non-SVR) (2016) | ★ | ★ | ★ | — | ★★ | ★ | ★ | ★ | 8 |
| Chen TM (SVR) (2016) | ★ | ★ | ★ | — | ★★ | ★ | ★ | ★ | 8 |
| Yu ML (2006) | ★ | ★ | ★ | — | ★★ | ★ | ★ | ★ | 8 |
A study can be awarded a maximum of two stars for comparability of cohorts on the basis of the design or analysis. A maximum of one star can be given for other seven items.