Table 4.
Assessment of bias risk using NOS scale for cohort study.
| References | 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 the study | Comparability of cohorts based on the design or analysis | Assessment of outcome | Was follow-up long enough for outcomes to occur | Adequacy of follow up of cohorts |
|---|---|---|---|---|---|---|---|---|
| Abji F, 2020 (70) | B* | A* | A* | A* | A* | B* | ||
| Abji F, 2020 (BMJ) (70) | B* | A* | A* | A* | B* | A* | A* | D |
| Chandran, 2013 (29) | B* | B* | A* | A* | A* | A* | ||
| Fuentelsaz-Romero, 2021 (76) | B* | A* | A* | A* | A* | A* | C | D |
| Inciarte-Mundo, 2018 (118) | B* | A* | B* | A* | B* | A* | A* | B* |
| Iwaszko, 2021 (41) | A* | A* | A* | A* | A* | A* | A* | A* |
| Wade, 2020 (40) | A* | A* | B* | A* | A* | B* | A* | D |
1) Representativeness of the exposed cohort A: truly representative of the average in the community*; B: somewhat representative of the average in the community*; C: selected group of users eg nurses, volunteers; D: no description of the derivation of the cohort.
2) Selection of the non-exposed cohort A: drawn from the same community as the exposed cohort* B: drawn from a different source; C: no description of the derivation of the non-exposed cohort.
3) Ascertainment of exposure A: secure record (eg surgical records)*; B: structured interview*; C: written self report; D: no description.
4) Demonstration that outcome of interest was not present at start of study A: yes* B: no.
5) Comparability of cohorts on the basis of the design or analysis A: study controls for … *; B: study controls for any additional factor*.
6) Assessment of outcome A: independent blind assessment*; B: record linkage*; C: self report; D: no description.
7) Was follow-up long enough for outcomes to occur A: yes (select an adequate follow up period for outcome of interest)*; B: no.
8) Adequacy of follow up of cohorts A: complete follow up - all subjects accounted for*; B: subjects lost to follow up unlikely to introduce bias*; C: follow up rate < ::% (select an adequate %) and no description of those lost; D: no statement.