Korner 2007.

Study characteristics
Patient sampling	Country Norway Study design Prospective cohort with retrospective sampling Setting Hospital Dates of data collection 1996 ‐ 1999 Population (n) 314 Inclusion criteria Surgically treated for adenocarcinoma of the colon or rectum with curative intent, age < 75 yrs, national guidelines followed Exclusion criteria Not systematically followed up for 5 years or until recurrence, incomplete CEA dataset. Dukes D Participants included (n) 153
Patient characteristics and setting	Age range < 75 Smoking status N/R Site of primary tumour Colon 102, rectum 50 Stage of primary tumour Dukes A 31, B 79, C 42 Perioperative investigations done to ensure no residual disease N/R Chemotherapy/radiotherapy? No Recurrences (n) 37 Site of recurrences N/R
Index tests	CEA timing CEA 3, 6, 9, 12, 18, 24, 30, 36, 42, 48, 54, 60 months CEA technique Immunoassay kit from Abbot diagnostic IL, USA CEA threshold 4 µg/L Definition of positive 1 elevated value Which CEA value (s) used? At time of recurrence
Target condition and reference standard(s)	Follow‐up schedule CEA 3, 6, 9, 12, 18, 24, 30, 36, 42, 48, 54, 60 months. USS Liver & CXR 6, 12, 18, 24, 30, 36, 42, 48, 54, 60 months. Colonoscopy 12, 60 months. Reference standard Biopsy and/or imaging studies to confirm recurrence, or disease‐free interval of 60 months without proof of recurrence.
Flow and timing	Timing of CEA vs reference standard (days) not specified if different from protocol
Comparative
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
Did the study avoid inappropriate exclusions?	No
		High	Low
DOMAIN 2: Index Test All CEA thresholds
If a threshold was used, was it pre‐specified?	Yes
Is the same method and instrument used for all CEA measurements?	Yes
Is there an estimation of reproducibility of the method, for example the % coefficient of variation at specific concentrations?	No
Is there an indication of method accuracy, for example, is there evidence of participation in an external quality assessment and proficiency testing scheme?	No
		Low	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	No
		Low	Low
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?	No
Were all patients included in the analysis?	Yes
Was the index test repeated prior to the reference standard?	No
Was the the timing between index test(s) and reference standard ascertainable?	Yes
Did all patients receive a reference standard?	Yes
		Low