Table 2. Newcastle-Ottawa quality assessment scale.

Selection
(1) Representativeness of the exposed cohort
(a) Truly representative of the average patients with colorectal cancers in the community*
(b) Somewhat representative of the average patients with colorectal cancers in the community*
(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
(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 (Proof of colorectal cancers and osteopontin measurement)
(a) Secure record (e.g., 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
Comparability
(1) Comparability of cohorts on the basis of the design or analysis
(a) Study controls for recurrence or metastasis*
(b) Study controls for any additional factor (Age, gender, grade, KPS score, etc.)*
Outcome
(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? (Death or recurrence)
(a) Yes (60 months)*
(b) No
(3) Adequacy of follow up of cohorts
(a) Complete follow up- all subjects accounted for*
(b) Subjects lost to follow up unlikely to introduce bias-small number lost- (25%) follow up, or description provided of those lost)*
(c) Follow up rate (<75%) and no description of those lost
(d) No statement

A maximum of one star (*)*: can be given for each numbereditem within the ‘Selection’ and ‘Outcome’ categories. While a maximum of twostars**: can be given for ‘Comparability’.