Table 3. Quality assessment of observational studies included in the meta-analysis using the New-Castle Ottawa scale.
| Author, year | Selection | Comparability | Outcome | Total score | |||||
| Representativeness of the exposed cohort | Selection of non-exposed cohort | Ascertainment of exposure | Demonstration that outcome was not present at the beginning | Comparability of groups | Assessment of outcome | Was follow up long enough for outcomes to occur? | Adequacy of follow up of cohorts | ||
| High-risk population | High-risk population | Surgery record on databases | Surgery record on databases | - | Blinded and independent | ≥6 months | ≥90% | ||
| Curro, 2012 [15] | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 7 |
| Llaguna, 2011 [14] | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 0 | 6 |
| Strzeczyk, 2002 [10] | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 7 |
| Argudo, 2018 [24] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
| Pereira, 2018 [25] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
| Blázquez-Hernando, 2016 [21] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
| Hoyuela, 2017 [22] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
| Rhemtulla, 2018 [6] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |