Fezoulidis 1987.

Study characteristics
Patient sampling	Country Germany Study design Prospective Setting Hospital Dates of data collection 1984 ‐ 1986 Population (n) 48 Inclusion criteria radical surgery Exclusion criteria No exclusion criteria were defined; results from all 48 participants are included in the study Participants Included (n) 48
Patient characteristics and setting	Age range Study does not describe age bands; median age is 64 Smoking status N/R Site of primary tumour Rectum Stage of primary tumour Dukes A 9, Dukes B 16, Dukes C1 19, Dukes C2 4 Perioperative investigations done to ensure no residual disease N/R Chemotherapy/radiotherapy? N/R Recurrences (n) 5 Site of recurrences 5 local rectal recurrences
Index tests	CEA timing 6 weeks, (then 3‐monthly); main text of the study only mentions that CEA was measured postoperatively; ?Only once; it is not clear if there was a sequence of measurements. Table 4 looks more like a one‐off CEA technique Unknown CEA threshold 2.5 µg/L Definition of positive Unclear Which CEA value (s) used? Probably 4 ‐ 6 weeks postoperatively
Target condition and reference standard(s)	Follow‐up schedule 4 ‐ 6 weeks postoperatively, then 3‐monthly clinical examination, CT, and CEA Reference standard 4 patients underwent CT guided biopsy but at unknown stage
Flow and timing	Timing of CEA vs reference standard (days) Unclear
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?	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?	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?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
		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?	Yes
Did all patients receive a reference standard?	Yes
		Low