Time of day variation in polyp detection rate for colonoscopies performed on a 3-hour shift schedule

  • Gregory W. Munson
    Current affiliations: Department of Gastroenterology, Mayo Clinic (G.W.M., D.L.F.), Rochester, Minnesota, USA; Department of Gastroenterology and Hepatology, Beaumont Hospital (G.C.H.), Dublin, Ireland
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  • Gavin C. Harewood
    Current affiliations: Department of Gastroenterology, Mayo Clinic (G.W.M., D.L.F.), Rochester, Minnesota, USA; Department of Gastroenterology and Hepatology, Beaumont Hospital (G.C.H.), Dublin, Ireland
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  • Dawn L. Francis
    Reprint requests: Dawn L. Francis, MD, MHS, Mayo Clinic, Division of Gastroenterology, 200 First Street SW, Rochester, MN 55905
    Current affiliations: Department of Gastroenterology, Mayo Clinic (G.W.M., D.L.F.), Rochester, Minnesota, USA; Department of Gastroenterology and Hepatology, Beaumont Hospital (G.C.H.), Dublin, Ireland
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Published:October 08, 2010DOI:


      Recent research suggests that the colonoscopy polyp detection rate (PDR) varies by time of day, possibly because of endoscopist fatigue. Mayo Clinic Rochester (MCR) schedules colonoscopies on 3-hour shifts, which should minimize fatigue.


      To examine PDR variation with the MCR shift schedule.


      Retrospective cohort.


      Outpatient tertiary-care center.


      This study involved completed outpatient colonoscopies in 2008. Procedures were excluded for lack of withdrawal time stamps, indications other than average-risk screening, inadequate bowel preparation, fellow participation, or performance by endoscopists with a low number of endoscopies performed.



      Main Outcome Measurements

      PDR (colonoscopies with ≥1 polyp divided by total number of colonoscopies) by shift of day.


      We analyzed 3846 colonoscopies. PDR varied significantly by shift (P = .008) on univariate analysis; results for shifts 1 and 3 were similar (39.0% vs 38.7%, respectively) whereas shift 2 had the highest PDR (44.7%). Mean withdrawal times were stable (P = .92). PDR also varied significantly (P < .0001) by month of year on univariate analysis. On multivariate analysis, patient age (P < .0001), patient gender (P < .0001), endoscopist mean withdrawal time (P < .0001), month of year (P = .0002), endoscopist experience (P = .04), and shift of day (P = .048) significantly predicted PDR.


      Retrospective study.


      MCR's 3-hour shift schedule does not show a decrease in PDR as the day progresses, as seen in other recent studies. Intervention trials at other institutions could determine whether alterations in shift length lead to PDR improvements.


      ADR (adenoma detection rate), MCR (Mayo Clinic Rochester), MERGE (Mayo Electronic Record for Gastrointestinal Endoscopy), PDR (polyp detection rate), WT (withdrawal time)
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