Miles 1995.

Study characteristics
Patient sampling	Country Scotland Study design Retrospective notes review Setting Hospital Dates of data collection 1988 ‐ 1992 Population (n) 265 Inclusion criteria Patients who underwent a resection, with curative intent. Exclusion criteria Patients were excluded where, on inspection of the patients' notes, it was found that primary surgery was palliative, follow‐up was incomplete or there were fewer than 1 preoperative and 2 postoperative carcinoembryonic antigen level estimations Participants included (n) 125
Patient characteristics and setting	Age range 69 (41 ‐ 90) Smoking status Unknown Site of primary tumour Colorectal Stage of primary tumour Dukes A 10, B 27, C 38, D 22, unknown 27 Perioperative investigations done to ensure no residual disease N/R Chemotherapy/radiotherapy? No Recurrences (n) 53 Site of recurrences N/R
Index tests	CEA timing Not clear CEA technique Using international standard International Reference Preparation 73/601, National Institute for Biological Standards and Control CEA threshold 10 µg/L Definition of positive 1 elevated value Which CEA value (s) used? All
Target condition and reference standard(s)	Follow‐up schedule History is recorded and clinical examination (including rectal examination and rigid sigmoidoscopy), faecal occult blood test and estimation of carcinoembryonic antigen level are undertaken Reference standard The presence of recurrent disease is confirmed by clinical examination, colonoscopy, biopsy, chest radiography, ultrasonography, computerized axial tomography scanning and laparotomy.
Flow and timing	Timing of CEA vs reference standard (days) per protocol, CEA triggers reference standard.
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?	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?	Yes
		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?	Unclear
		Low	Low
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?	No
		High