Table 2 Quality assessment of eligible studies using the Newcastle-Ottawa quality assessment.

From: The prognostic significance of PD-L1 expression in patients with glioma: A meta-analysis

Lead author (y)

Selection†

Comparability‡

Outcome§

Total scores

Liu, Y. et al.9

3

1

2

6

Berghoff, A. S. et al.11

3

2

2

7

Nduom, E. K et al.10

3

2

2

7

Zeng, J. et al.12

3

2

3

8

  1. †Selection (0~4 points).
  2. (1) Representativeness of the exposed cohort (1 point, truly or somewhat representative of the average level in the community; 0 point, selected group of users or no description of the derivation of the cohort).
  3. (2) Selection of the non-exposed cohort (1 point, drawn from the same community as the exposed cohort; 0 point, drawn from a different source or no description of the derivation of the non-exposed cohort).
  4. (3) Ascertainment of exposure (1 point, secure record or structured interview; 0 point, written self-report or no description).
  5. (4) Demonstration that outcome of interest was not present at start of study (1 point, yes; 0 point, no).
  6. ‡Comparability (0~2 points) (2 points, study controls for the most important factor and any additional factor; 1 point, study controls for the most important factor or any additional factor; 0 point, study controls without the most important factor or any additional factor).
  7. §Outcome (0~3 points).
  8. (1) Assessment of outcome (1 point, independent blind assessment or record linkage; 0 point, self-report or no description).
  9. (2) Was follow-up long enough for outcomes to occur (1 point, yes; 0 point, no).
  10. (3) Adequacy of follow up of cohorts (1 point, complete follow up or subjects lost to follow up unlikely to introduce bias; 0 point, follow up rate <80% and no description of those lost, or no statement).
  11. The quality score was ranked as low (≤5points) or high (≥6 points).
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