title: Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
abstract: OBJECTIVE
  One objective of colonoscopy is to identify and remove polyps-this process requires attention to detail and prolonged concentration. Providers are predisposed to cognitive errors because the procedure is often performed repetitively throughout the day. We measured the adjusted relationship between colonoscopy start time and polyp yield.
  
  
  METHODS
  We performed a prospective study of 477 patients that received screening, surveillance, or diagnostic colonoscopies at a Veteran's Administration (VA) teaching hospital. The primary outcome measure was polyp yield. We collected data on colonoscopy start times, which were analyzed both as a dichotomous time period ("early-morning case" vs "later case") and as a continuous variable (start time). We identified significant risk factors using univariate analysis and performed Poisson multivariable regression to measure the independent effect of colonoscopy start time on polyp yield. We evaluated evidence of decreasing polyp yield as the day progressed throughout pre-specified time intervals.
  
  
  RESULTS
  In univariate analysis, early-morning cases yielded 27% more polyps per patient than later cases (95% confidence interval, 11%-45%; P < .001). The total numbers of, hyperplastic and adenomatous polyps found decreased hour-by-hour as the day progressed. Multivariable analysis demonstrated that early-morning cases yielded 20% more polyps per patient than later cases (95% confidence interval, 5%-38%; P = .007).
  
  
  CONCLUSIONS
  At a VA medical center, more polyps were detected in patients that received colonoscopies early in the morning compared with later in the day. Moreover, adenoma detection reduced as the day progressed. Providers might be most adept at detecting polyps at the beginning of the day; further validation in other practice settings is required.
authors.affiliation: Division of Digestive Diseases, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Chan
authors.forename: Hartley
authors.initials: H
authors.lastname: Cohen
authors.forename: Brennan M R
authors.initials: BM
authors.lastname: Spiegel
mesh_terms: D000236:Adenoma / Q000175:diagnosis*; D000368:Aged; D003110:Colonic Neoplasms / Q000175:diagnosis*; D003113:Colonoscopy; D003951:Diagnostic Errors / Q000706:statistics & numerical data*; D005260:Female; D006302:Health Services Research; D006784:Hospitals, Teaching; D006787:Hospitals, Veterans; D006801:Humans; D008297:Male; D008875:Middle Aged; D011127:Polyps / Q000175:diagnosis*; D011446:Prospective Studies; D013997:Time Factors