Tate 1982.

Study characteristics
Patient sampling	Country UK Study design Prospective study after some retrospective sampling Setting Hospital Dates of data collection 1973 ‐ 1978 Population (n) 520 Inclusion criteria curative resection Exclusion criteria Dukes D, no follow‐up information available, signs of malignancy on first postoperative examination, malignancy of other sites during follow‐up Participants Included (n) 468
Patient characteristics and setting	Age range N/R Smoking status N/R Site of primary tumour N/R Stage of primary tumour A 94, B 226, C 128, unknown 20 Perioperative investigations done to ensure no residual disease First postoperative exam Chemotherapy/radiotherapy? Not stated Recurrences (n) 108 Site of recurrences N/R
Index tests	CEA timing At each follow‐up visit CEA technique Assayed by a double‐antibody radioimmunoassay system CEA threshold 40 µg/L Definition of positive 1 elevated value Which CEA value (s) used? all
Target condition and reference standard(s)	Follow‐up schedule The follow‐up procedure for each patient complied with the normal clinical practice for the hospital concerned and, in addition, at each follow up examination a specimen of plasma was taken for CEA determination. At least 6mly. Reference standard Variable
Flow and timing	Timing of CEA vs reference standard (days) Very variable
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?	Unclear
Were the reference standard results interpreted without knowledge of the results of the index tests?	Yes
		Unclear	Unclear
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?	No
Did all patients receive a reference standard?	Unclear
		Unclear