Engarås 2003.

Study characteristics
Patient sampling	Country Sweden Study design Prospective Setting Hospital Dates of data collection 1998 ‐ 1990 Population (n) 151 Inclusion criteria Surgery with curative intent with 5 years follow‐up Exclusion criteria N/R Participants Included (n) 132
Patient characteristics and setting	Age range 27 ‐ 75 Smoking status N/R Site of primary tumour Colorectal Stage of primary tumour Duke A 11, B 76, C 43,D 1, Undefined 1 Perioperative investigations done to ensure no residual disease Not specified Chemotherapy/radiotherapy? N/R Recurrences (n) 39 Site of recurrences N/R
Index tests	CEA timing Monthly during year 1 and then at 18 and 24 months CEA technique Delfia® test kits (Wallac Oy, Turku, Finland). The accuracy of the assays was assessed by analysis of 2 control samples in each assay and by measurement of the coefficient of variation by duplicate analyses of the samples CEA threshold 5.6 µg/L Definition of positive 1 elevated value Which CEA value (s) used? All
Target condition and reference standard(s)	Follow‐up schedule Monthly outpatient clinic visit during year 1, serum tests monthly during year 1, then 18 and 24 months. Clinical examinations at 1 year and 2 year with CXR, Sigmoidoscopy, BE, and CT Liver. Reference standard Radiologic and/or endoscopic investigations at surgery or post mortem
Flow and timing	Timing of CEA vs reference standard (days) as per follow‐up schedule
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?	Unclear
Did the study avoid inappropriate exclusions?	Unclear
		Unclear	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?	Yes
Is there an indication of method accuracy, for example, is there evidence of participation in an external quality assessment and proficiency testing scheme?	Yes
		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?	Yes
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?	No
Did all patients receive a reference standard?	Yes
		Low