title: Experience with a two-tier reflex gFOBT/FIT strategy in a national bowel screening programme.
abstract: OBJECTIVE
  To evaluate a two-tier reflex guaiac-based faecal occult blood test (gFOBT)/faecal immunochemical test (FIT) algorithm in screening for colorectal cancer.
  
  
  METHODS
  Fourth screening round in NHS Tayside (Scotland).
  
  
  METHODS
  gFOBT were sent to 50-74-year-olds. Participants with five or six windows positive were offered colonoscopy. Participants with one to four windows positive were sent a FIT and, if positive, were offered colonoscopy. Participants providing an untestable gFOBT were sent a FIT and, if positive, were offered colonoscopy. Outcomes following positive results, cancer stages and key performance indicators were assessed.
  
  
  RESULTS
  Of 131,885 invited, 73,315 (55.6%) responded. There were 66,957 (91.3%) negative, 241 (0.3%) strong positive, 5230 (7.1%) weak positive and 887 (1.2%) untestable results. The 241 participants who had five or six windows positive had more cancers than those positive by other routes: only 3 of the 30 cancers (9.7%) were Dukes' A. Among the 983 positive results from the weak positive gFOBT then positive FIT route, there were fewer cancers and more normal colonoscopies, but more adenomas than in the group with a strong positive gFOBT. In those with an untestable gFOBT, 77 had a positive FIT result, with fewer true and more false positive results than in the other groups. Fewer males had cancer and stages were earlier than in females, but more had adenoma. The detection rate for cancer was 0.18% and the PPV for cancer and all adenomas was 41.3%.
  
  
  CONCLUSIONS
  The algorithm and FIT following a weak positive gFOBT have advantages. FIT following an untestable gFOBT warrants review.
authors.affiliation: Centre for Research into Cancer Prevention & Screening, University of Dundee Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland. callum.fraser@nhs.net
authors.forename: Callum G
authors.initials: CG
authors.lastname: Fraser
authors.forename: Jayne
authors.initials: J
authors.lastname: Digby
authors.forename: Paula J
authors.initials: PJ
authors.lastname: McDonald
authors.forename: Judith A
authors.initials: JA
authors.lastname: Strachan
authors.forename: Francis A
authors.initials: FA
authors.lastname: Carey
authors.forename: Robert J C
authors.initials: RJ
authors.lastname: Steele
mesh_terms: D000236:Adenoma / Q000175:diagnosis* / Q000453:epidemiology; D000368:Aged; D003113:Colonoscopy / Q000379:methods / Q000706:statistics & numerical data; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology; D055088:Early Detection of Cancer / Q000379:methods; D005243:Feces / Q000737:chemistry; D005260:Female; D006138:Guaiac; D006801:Humans; D007120:Immunochemistry / Q000379:methods*; D008297:Male; D008403:Mass Screening / Q000379:methods* / Q000706:statistics & numerical data; D008875:Middle Aged; D009780:Occult Blood; D012018:Reflex / Q000502:physiology; D012189:Retrospective Studies; D012606:Scotland / Q000453:epidemiology; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D006138:Guaiac