McCall 1994.

Study characteristics
Patient sampling	Country Australia Study design Prospective RCT Setting Hospital Dates of data collection 1984 ‐ 1990 Population (n) 328 Inclusion criteria curative resection of colorectal cancers Exclusion criteria Patients with metastatic disease at presentation and those who for geographic or medical reasons were not able to be followed were excluded from the trial. Less than two years follow‐up completed (16 patients: 10 died of unrelated causes; 6 withdrew consent or were lost to follow‐up) and failure to obtain CEA levels (one patient). Participants Included (n) 311
Patient characteristics and setting	Age range N/R Smoking status N/R Site of primary tumour Colorectal Stage of primary tumour Dukes ABC Perioperative investigations done to ensure no residual disease N/R Chemotherapy/radiotherapy? N/R Recurrences (n) 98 Site of recurrences N/R
Index tests	CEA timing Patients entered into both arms of the study had serum CEA levels measured for 5 consecutive years: every 3 months for the first 2 years, then every 6 months for the next 3 years CEA technique Enzyme immunoassay method (Abbott Laboratories, North Chicago, IL) CEA threshold 5 µg/L Definition of positive 1 elevated value Which CEA value (s) used? All
Target condition and reference standard(s)	Follow‐up schedule Standard follow up: Clinical review plus CEA, Liver function, and fecal occult blood ‐ 3 monthly til 2 years, 6 monthly til 5 years. CXR, Liver CT, Colonoscopy at 0 and 5 years; Aggressive follow up: As for standard follow‐up plus CXR , Liver CT and Colonoscopy annually Reference standard Radiology, histology
Flow and timing	Timing of CEA vs reference standard (days) per 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?	Yes
		Low	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?	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