Seregni 1992.

Study characteristics
Patient sampling	Country Italy Study design Retrospective Setting Hospital Dates of data collection 1975 ‐ 1990 Population (n) 431 Inclusion criteria Curative resection Exclusion criteria N/R Participants Included (n) 336
Patient characteristics and setting	Age range 21 ‐ 92 Smoking status N/R Site of primary tumour Colon 247, rectum 184 Stage of primary tumour Dukes A 40, B 186, C 107, D 72 Perioperative investigations done to ensure no residual disease N/R Chemotherapy/radiotherapy? N/R Recurrences (n) 136 Site of recurrences 50 local recurrences, 136 distant recurrences
Index tests	CEA timing N/R CEA technique N/R CEA threshold N/R Definition of positive Unclear Which CEA value (s) used? Unclear
Target condition and reference standard(s)	Reference standard N/R
Flow and timing	Timing of CEA vs reference standard (days) N/R
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?	No
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?	Unclear
Is the same method and instrument used for all CEA measurements?	Unclear
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
		Unclear	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?	Unclear
		Unclear	Unclear
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?	Unclear
Were all patients included in the analysis?	Yes
Was the index test repeated prior to the reference standard?	Unclear
Was the the timing between index test(s) and reference standard ascertainable?	Unclear
Did all patients receive a reference standard?	Unclear
		Unclear