title: Performance of the colorectal cancer screening marker Sept9 is influenced by age, diabetes and arthritis: a nested case-control study.
abstract: BACKGROUND
  Annually, colorectal cancer (CRC) is diagnosed in >1.4 million subjects worldwide and incidence is increasing. Much effort has therefore been focused on screening, which has proven to reduce cancer-related mortality. The Sept9 DNA-methylation assay is among the most well studied blood-based screening markers. However, earlier reported performances may be misleading: the Sept9 test was recently examined in two screening based cohorts and yielded performances lower than expected. We hypothesize that comorbidities and/or demographic characteristics affect the results of the Sept9 test.
  
  
  METHODS
  Using a retrospective nested case-control study design, we studied plasma from 150 cancer and 150 controls selected from a well-characterized cohort of 4698 subjects referred for diagnostic colonoscopy due to CRC-related symptoms. The cases and controls were matched on age and gender, and moreover cases were stratified on tumor-site and tumor-stage. The selected cohort included a wide range of comorbidities. Plasma Sept9 levels were assessed using a commercially available PCR based assay (Epi-proColon).
  
  
  RESULTS
  Clinical sensitivity for CRC stages I-IV was 37 %, 91 %, 77 %, and 89 %, and the overall sensitivity 73 % (95 % CI, 64-80 %) and specificity 82 % (95 % CI, 75-88 %), respectively. Age >65 was associated with both increased false positive and false negative results (p < 0.05). Arthritis was associated with a higher false negative rate (p = 0.005) whereas Arteriosclerosis was associated with a higher false positive rate (p = 0.007). Diabetes was associated with Sept9 positivity with an OR of 5.2 (95 % CI 1.4-19.1). When the performance of Sept9 was adjusted for these parameters in a final multivariate regression model, the OR for a positive Sept9 test to be associated with CRC increased from 8.25 (95 % CI 4.83-14.09) to 29.46 (95 % CI 12.58-69.02).
  
  
  CONCLUSIONS
  The results indicate that the performance of the Sept9 assay is negatively affected by several factors commonly associated with CRC screening populations: early-stage disease, age > 65 years, diabetes, arthritis, and arteriosclerosis. This should be taken into account if the Sept9 assay is used as a single marker for CRC screening, but may also have a wider impact, as it is likely that such factors may affect other blood based DNA markers as well.
authors.affiliation: Department of Molecular Medicine, MOMA, Aarhus University Hospital, Skejby, DK-8200, Aarhus N, Denmark. mwo@clin.au.dk.
authors.forename: Mai-Britt W
authors.initials: MB
authors.lastname: Ørntoft
authors.affiliation: Department of Surgical Gastroenterology 360, Hvidovre Hospital, University of Copenhagen, DK-2650, Hvidovre, Denmark. h.j.nielsen360@gmail.com.
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Nielsen
authors.affiliation: Department of Molecular Medicine, MOMA, Aarhus University Hospital, Skejby, DK-8200, Aarhus N, Denmark. tfo@clin.au.dk.
authors.forename: Torben F
authors.initials: TF
authors.lastname: Ørntoft
authors.affiliation: Department of Molecular Medicine, MOMA, Aarhus University Hospital, Skejby, DK-8200, Aarhus N, Denmark. cla@clin.au.dk.
authors.forename: Claus L
authors.initials: CL
authors.lastname: Andersen
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001168:Arthritis; D014408:Biomarkers, Tumor; D016022:Case-Control Studies; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics*; D015897:Comorbidity; D003920:Diabetes Mellitus; D055088:Early Detection of Cancer / Q000379:methods / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D015203:Reproducibility of Results; D012307:Risk Factors; D058112:Septins / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; C474315:SEPTIN9 protein, human; D058112:Septins