title: Diagnostic interval and mortality in colorectal cancer: U-shaped association demonstrated for three different datasets.
abstract: OBJECTIVE
  To test the theory of a U-shaped association between time from the first presentation of symptoms in primary care to the diagnosis (the diagnostic interval) and mortality after diagnosis of colorectal cancer (CRC).
  
  
  METHODS
  Three population-based studies in Denmark and the United Kingdom using data from general practitioner's questionnaires, interviewer-administered patient questionnaires, and primary care records, respectively.
  
  
  RESULTS
  Despite variations in the potential selection and information bias when using different methods of identifying the date of first presentation, the association between the length of the diagnostic interval and 5-year mortality rate after the diagnosis of CRC was the same for all three types of data: displaying a U-shaped association with decreasing and subsequently increasing mortality with longer diagnostic intervals.
  
  
  CONCLUSIONS
  Unknown confounding and in particular confounding by indication is likely to explain the counterintuitive findings of higher mortality among patients with very short diagnostic intervals, but cannot explain the increasing mortality with longer diagnostic intervals. The results support the theory that longer diagnostic intervals cause higher mortality in patients with CRC.
authors.affiliation: The Research Unit for General Practice, The Research Centre for Cancer Diagnosis in Primary Care, Aarhus University, DK-8000 Aarhus, Denmark. mlt@alm.au.dk
authors.forename: Marie Louise
authors.initials: ML
authors.lastname: Tørring
authors.forename: Morten
authors.initials: M
authors.lastname: Frydenberg
authors.forename: William
authors.initials: W
authors.lastname: Hamilton
authors.forename: Rikke P
authors.initials: RP
authors.lastname: Hansen
authors.forename: Marianne D
authors.initials: MD
authors.lastname: Lautrup
authors.forename: Peter
authors.initials: P
authors.lastname: Vedsted
mesh_terms: D000328:Adult; D000368:Aged; D015982:Bias; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000401:mortality*; D057210:Delayed Diagnosis; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011320:Primary Health Care; D011787:Quality of Health Care; D012107:Research Design; D011795:Surveys and Questionnaires; D015996:Survival Rate; D013997:Time Factors; D006113:United Kingdom / Q000453:epidemiology