title: The yield of a second screening flexible sigmoidoscopy in average-risk persons after one negative examination.
abstract: OBJECTIVE
  The American Cancer Society recommends that asymptomatic persons aged > or = 50 years undergo sigmoidoscopy every 3-5 years. However, the yield of a second examination 3 years later in persons who are initially negative is unknown. The aim of this study was to determine the yield of a second flexible sigmoidoscopy in average-risk persons aged > or = 50 years after an initial negative examination.
  
  
  METHODS
  Two hundred fifty-nine asymptomatic, average-risk persons who had undergone a negative screening flexible sigmoidoscopy examination at age > or = 50 years underwent a second examination at least 2 years later (mean, 3.4 years).
  
  
  RESULTS
  The second examination found adenomas in 15 (6%) screenees, but no cancers or large (> 1 cm) or severely dysplastic adenomas were detected. Persons aged > or = 60 years at the time of the second examination were more likely (10%) to have adenomas than those < 60 years (3%) (odds ratio, 3.76; 95% confidence interval, 1.17-12.2), but no advanced lesions were found in persons aged > or = 60 years.
  
  
  CONCLUSIONS
  These data suggest that the American Cancer Society should consider changing its recommendation for screening flexible sigmoidoscopy in asymptomatic, average-risk persons to 5-year intervals after a negative examination.
authors.affiliation: Department of Medicine, Indiana University School of Medicine, Indianapolis.
authors.forename: D K
authors.initials: DK
authors.lastname: Rex
authors.forename: G A
authors.initials: GA
authors.lastname: Lehman
authors.forename: T M
authors.initials: TM
authors.lastname: Ulbright
authors.forename: J J
authors.initials: JJ
authors.lastname: Smith
authors.forename: R H
authors.initials: RH
authors.lastname: Hawes
mesh_terms: D000236:Adenoma / Q000453:epidemiology*; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D012812:Sigmoidoscopy; D013997:Time Factors