2. Newcastle‐Ottawa quality assessment scale.

Scale

Cohort studies Note: A study can be awarded a maximum of 1 star for each numbered item within the Selection and Outcome categories. A maximum of 2 stars can be given for Comparability. A total of 9 stars can be awarded. Selection 1. Representativeness of the exposed cohort (1 star*) a) Truly representative of the exposed cohort b) Somewhat representative of the exposed cohort c) Selected group of users, e.g. nurses, volunteers d) No description of the derivation of the cohort 2. Selection of the non‐exposed cohort (1 star*) 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 (1 star*) a) Secure record b) Structured interview c) Written self‐report d) No description 4. Demonstration that outcome of interest was not present at start of study (1 star*) a) Yes b) No Comparability 1. Comparability of cohorts on the basis of the design or analysis (max 2 stars**) a) Study controls for age b) Study controls for time on chemotherapy Outcome (1 star*) 1. Assessment of outcome a) Independent blind assessment b) Record linkage c) Self‐report d) No description 2. Was follow‐up long enough for outcomes to occur? (1 star*) (1) Yes (2) No 3. Adequacy of follow‐up of cohorts (1 star*) a) Complete follow‐up ‐ all participants accounted for b) Participants lost to follow‐up unlikely to introduce bias ‐ small number lost > 80% follow‐up c) Follow‐up rate < 80% and no description of those lost d) No statement