Johnson 1985.

Study characteristics
Patient sampling	Country Norway Study design Propsective Setting Hosptial + primary care Dates of data collection N/R Population (n) 93 Inclusion criteria Radical treatment for colorectal cancer Exclusion criteria Palliative, new cancers, no CEA monitoring Participants included (n) 51
Patient characteristics and setting	Age range N/R Smoking status N/R Site of primary tumour Colon 49, rectal 44 Stage of primary tumour Dukes A 28, B 27, C 21, palliative 17 Perioperative investigations done to ensure no residual disease N/R Chemotherapy/radiotherapy? N/R Recurrences (n) 15 Site of recurrences N/R
Index tests	CEA timing Postoperatively, then at 3 ‐ 4‐monthly intervals CEA technique N/R CEA threshold 5 µg/L Definition of positive N/R Which CEA value (s) used? N/R More data available? N/R
Target condition and reference standard(s)	Follow‐up schedule Postoperatively, then at 3 ‐ 4 monthly intervals, rising CEA resulted in further investigation, general clinical investigations, angiography of the liver, resection. No fixed schedule
Flow and timing	Timing of CEA vs reference standard (days) CEA triggered investigation
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?	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?	No
		Unclear	Unclear
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?	No
Were all patients included in the analysis?	Unclear
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