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Does time of day affect polyp detection rates from colonoscopy?

  • Brennan M.R. Spiegel
    Affiliations
    Veterans Affairs Greater Los Angeles Healthcare System, David Geffen School of Medicine, University of California Los Angeles, CURE Digestive Diseases Research Center, University of California Los Angeles/Veterans Affairs Center for Outcomes Research and Education, Los Angeles, California, USA
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      Abbreviations:

      PDR (polyp detection rate), VA (Veterans Affairs)
      Although there are several approaches to colorectal cancer screening, colonoscopy is the only test that allows identification and removal of polyps from the entire colon.
      • Winawer S.
      • Fletcher R.
      • Rex D.
      • et al.
      Colorectal cancer screening and surveillance: clinical guidelines and rationale: update based on new evidence.
      Colonoscopic polypectomy is associated with a reduction in colorectal cancer versus no polypectomy.
      • Winawer S.J.
      • Zauber A.G.
      • Ho M.N.
      • et al.
      National Polyp Study Workgroup
      Prevention of colorectal cancer by colonoscopic polypectomy.
      • Muller A.D.
      • Sonnenberg A.
      Protection by endoscopy against death from colorectal cancer: a case-control study among veterans.
      • Selby J.V.
      • Friedman G.D.
      • Quesenberry Jr, C.P.
      • et al.
      A case-control study of screening sigmoidoscopy and mortality from colorectal cancer.
      • Citarda F.
      • Tomaselli G.
      • Capocaccia R.
      • et al.
      Efficacy in standard clinical practice of colonoscopic polypectomy in reducing colorectal cancer incidence.
      Yet colonoscopy is an imperfect test. Adenoma detection rates depend on examiner experience and skill, including the ability to reliably intubate the cecum, the willingness to slow withdrawal time as needed to carefully examine the mucosa, and the capacity to consistently identify often subtle polyposis.
      • Barclay R.L.
      • Vicari J.J.
      • Doughty A.S.
      • et al.
      Colonoscopic withdrawal times and adenoma detection during screening colonoscopy.
      • Rex D.K.
      • Bond J.H.
      • Winawer S.
      • et al.
      Quality in the technical performance of colonoscopy and the continuous quality improvement process for colonoscopy: recommendations of the U.S. Multi-Society Task Force on Colorectal Cancer.
      Successful colonoscopy also requires that patients effectively evacuate their bowels through the proper use of purgatives and adherence to strict dietary restrictions.
      • Harewood G.C.
      • Sharma V.K.
      • de Garmo P.
      Impact of colonoscopy preparation quality on detection of suspected colonic neoplasia.
      • Froehlich F.
      • Wietlisbach V.
      • Gonvers J.J.
      • et al.
      Impact of colonic cleansing on quality and diagnostic yield of colonoscopy: the European Panel of Appropriateness of Gastrointestinal Endoscopy European multicenter study.
      Additional factors include patient body mass index, adequacy of sedation, and patient history of abdominal surgery, among other variables.
      • Rex D.K.
      • Bond J.H.
      • Winawer S.
      • et al.
      Quality in the technical performance of colonoscopy and the continuous quality improvement process for colonoscopy: recommendations of the U.S. Multi-Society Task Force on Colorectal Cancer.
      • Harris J.K.
      • Froehlich F.
      • Wietlisbach V.
      • et al.
      Factors associated with the technical performance of colonoscopy: an EPAGE study.
      In short, the success of colonoscopy depends on a wide range of patient, provider, and procedural characteristics.
      The effectiveness of colonoscopy for detecting polyps may also depend, in part, on when the procedure is performed. Our group recently found that polyp yield from colonoscopy decreased hour-by-hour throughout endoscopic work shifts in a university-based Veterans Affairs (VA) medical center.
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      Patients undergoing early morning procedures had more overall polyps and histologically confirmed adenomas than later cases; this effect persisted after we controlled for bowel preparation quality, withdrawal time, cecal intubation, indication, endoscopist, and patient characteristics.
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      Moreover, the effect was not just a morning versus afternoon phenomenon—it occurred throughout the day and persisted within continuous work shifts restricted to morning hours alone.
      There has been a growing body of other studies regarding adenoma detection rates and time of day. For example, Sanaka et al
      • Sanaka M.R.
      • Deepinder F.
      • Thota P.N.
      • et al.
      Adenomas are detected more often in morning than in afternoon colonoscopy.
      detected a negative relationship between time of day and adenoma yield after adjusting for bowel preparation quality in a non-VA university-based center. A third study, also from a non-VA center, found the same relationship and specifically revealed that a later position in the endoscopic work queue strongly predicted lower polyp detection within a shift
      • Lee A.G.N.
      • Iskander J.M.
      • Borg B.B.
      • et al.
      Queue position in the day's endoscopic schedule impacts effectiveness of colonoscopy.
      ; that is, as more cases accrued during a continuous shift, endoscopists became less likely to find adenomas in the next colonoscopy performed.
      The within- versus between-shift distinction is important, because analyses limited to within a shift may yield results different from those of analyses that compare outcomes between shifts. For example, it is entirely possible that the polyp detection rate (PDR) might fall during a shift, as demonstrated by the Chan et al
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      and Lee et al
      • Lee A.G.N.
      • Iskander J.M.
      • Borg B.B.
      • et al.
      Queue position in the day's endoscopic schedule impacts effectiveness of colonoscopy.
      studies, and that simultaneously there may be no differences in PDRs between shifts—these are not mutually exclusive findings. If we compare adenoma detection rates by using the morning versus afternoon dichotomy, then we might not expect any differences after controlling for variations in preparation quality, especially if a new group of endoscopists takes over during the afternoon shift. The “fatigue clock” would reset when a new group arrives or after a break, so merely comparing adenoma yield in morning versus afternoon shifts might not be expected to detect differences. In contrast, a more useful study would be to evaluate PDRs within a single shift by continuous time intervals, not between shifts, because only the former can tap into the fatigue issue that may be driving this phenomenon.
      There are other data as well to suggest a relationship between time of day and polyp yield. A fourth study, conducted in a community-based nonteaching facility, found a statistically significant 34% higher odds of detecting a polyp in the morning versus the afternoon (despite its title “Rates of polyp and adenoma detection during screening colonoscopy are not significantly affected by time of day”).
      • Balz J.L.V.
      • Patrie J.T.
      • Crowe S.E.
      Rates of polyp and adenoma detection during screening colonoscopy are not significantly affected by time of day.
      However, when the study focused only on adenomas, there was a nonsignificant 17% increase in the odds of adenoma detection, although the study did not report hour-by-hour trends within shifts (in contrast to between shifts separated by a work break).
      In short, based on multiple studies, it remains possible that some providers are more adept at detecting polyps earlier in a work shift, at least in academic teaching facilities. This last point is also important—the phenomenon may be especially prevalent in teaching units. Further research should provide within-shift data in nonteaching facilities as well and should measure these data by using the same analytic techniques used by Lee et al
      • Lee A.G.N.
      • Iskander J.M.
      • Borg B.B.
      • et al.
      Queue position in the day's endoscopic schedule impacts effectiveness of colonoscopy.
      to measure position in the work queue as a predictor of polyp yield.
      It is possible that the decreased polyp yield over time results from cognitive or perceptual errors from exposure to a prolonged and repetitive activity.
      Committee on Quality of Health Care in America, Institute of Medicine
      Although earlier studies did not measure provider fatigue during the colonoscopies, we previously attempted to examine other potential explanations that might undermine the relationship. For example, it is possible that providers might speed up as the day progresses. However, we found no difference in withdrawal time as the day progressed.
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      Similarly, the results might arise from differences in patient-level characteristics and risk factors. However, we found no differences over time periods for patient age, personal or family history of colorectal cancer, body mass index, or history of abdominal surgery.
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      It might also be possible that some endoscopists are more skilled than others and that skilled endoscopists are more likely to perform procedures earlier in the day. However, we found no systematic differences in the distribution of endoscopists as the day progressed.
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      Although higher cecal intubation rates and better preparation quality were evident in the morning hours, this disparity only partly explained the overall results. Indeed, the relationship between time of day and colonoscopy yield persisted despite adjusting for these imbalances; this suggests, but does not prove, that distraction, fatigue, or perceptual errors might be at play. This also has been hypothesized in a study from Ireland evaluating the effect of procedure chronology on quality benchmarks in patients undergoing colonoscopy.
      • Harewood G.C.
      • Chrysostomou K.
      • Himy N.
      • et al.
      Impact of operator fatigue on endoscopy performance: implications for procedure scheduling.
      Those authors concluded that cecal intubation rates declined with successive procedures, and they attributed this finding to operator fatigue.
      • Harewood G.C.
      • Chrysostomou K.
      • Himy N.
      • et al.
      Impact of operator fatigue on endoscopy performance: implications for procedure scheduling.
      So there are now data from teaching,
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      • Sanaka M.R.
      • Deepinder F.
      • Thota P.N.
      • et al.
      Adenomas are detected more often in morning than in afternoon colonoscopy.
      nonteaching,
      • Balz J.L.V.
      • Patrie J.T.
      • Crowe S.E.
      Rates of polyp and adenoma detection during screening colonoscopy are not significantly affected by time of day.
      VA,
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      non-VA,
      • Sanaka M.R.
      • Deepinder F.
      • Thota P.N.
      • et al.
      Adenomas are detected more often in morning than in afternoon colonoscopy.
      • Lee A.G.N.
      • Iskander J.M.
      • Borg B.B.
      • et al.
      Queue position in the day's endoscopic schedule impacts effectiveness of colonoscopy.
      • Balz J.L.V.
      • Patrie J.T.
      • Crowe S.E.
      Rates of polyp and adenoma detection during screening colonoscopy are not significantly affected by time of day.
      • Harewood G.C.
      • Chrysostomou K.
      • Himy N.
      • et al.
      Impact of operator fatigue on endoscopy performance: implications for procedure scheduling.
      U.S.,
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      • Sanaka M.R.
      • Deepinder F.
      • Thota P.N.
      • et al.
      Adenomas are detected more often in morning than in afternoon colonoscopy.
      • Lee A.G.N.
      • Iskander J.M.
      • Borg B.B.
      • et al.
      Queue position in the day's endoscopic schedule impacts effectiveness of colonoscopy.
      • Balz J.L.V.
      • Patrie J.T.
      • Crowe S.E.
      Rates of polyp and adenoma detection during screening colonoscopy are not significantly affected by time of day.
      and European
      • Harewood G.C.
      • Chrysostomou K.
      • Himy N.
      • et al.
      Impact of operator fatigue on endoscopy performance: implications for procedure scheduling.
      centers that at least raise time of day as a possible factor affecting colonoscopy outcomes.
      Fatigue is well known to affect outcomes in other fields marked by repetitive activities. In trucking, for example, drivers are more likely to cross yellow lines the longer they drive.
      • Philip P.
      • Taillard J.
      • Moore N.
      • et al.
      The effects of coffee and napping on nighttime highway driving: a randomized trial.
      In the airline industry, cockpit and air traffic control errors accrue during the end of work shift—a fact addressed by the Federal Aviation Administration through extensive work-shift regulations.
      Federal Aviation Administration
      A review of issues concerning duty period limitations, flight time limitations, and rest requirements.
      In anesthesia and surgery, operating room complications tend to increase as work shifts progress.
      • Howard S.K.
      • Rosekind M.R.
      • Katz J.D.
      • et al.
      Fatigue in anesthesia: implications and strategies for patient and provider safety.
      • Taffinder N.J.
      • McManus I.C.
      • Gul Y.
      • et al.
      Effect of sleep deprivation on surgeons' dexterity on laparoscopy simulator.
      • Eastridge B.J.
      • Hamilton E.C.
      • O'Keefe G.E.
      • et al.
      Effect of sleep deprivation on the performance of simulated laparoscopic surgical skill.
      And it is well documented that house officers make more errors the longer they are in the hospital
      • Gaba D.M.
      • Howard S.K.
      Patient safety: fatigue among clinicians and the safety of patients.
      —a possible explanation for the colonoscopy results that seem to be emerging from teaching facilities, in particular. But given the prolonged, oftentimes repetitious, and sometimes distractible nature of outpatient colonoscopy, it is possible that cognitive errors happen in the endoscopy suite just as they occur in other prolonged and repetitious activities. As endoscopists, perhaps we should at least consider the possibility, even if we otherwise feel self-assured that it “doesn't happen with me.”
      If this effect is real, then we should determine how it can be reversed, at least in settings where it is occurring. One solution might be to set a cap on the duration of endoscopic work shifts; this is practiced in the Rochester Mayo Clinic, where each day is divided into 3 shifts of 3 hours each. In this issue of Gastrointestinal Endoscopy, Munson et al
      • Munson G.W.
      • Harewood G.C.
      • Francis D.L.
      Time of day variation in polyp detection rate for colonoscopies performed on a 3-hour shift schedule.
      present new data regarding time of day variations in polyp detection for colonoscopies performed within the Mayo Clinic scheduling system. The authors measured differences in polyp (not adenoma) detection by using very short 3-hour-capped work shifts: 7:30 to 10:30 am; 10:30 am to 1:30 pm; and 1:30 to 4:30 pm. The authors hypothesized that short work shifts might reduce fatigue and stabilize the relationship between time of day and polyp yield.
      In a large series of 3864 colonoscopies, Munson et al found differences in polyp detection rates among shifts throughout the day (P = .008 for difference in PDR). Specifically, the first and last shifts were similar (39% vs 38.7% PDR, respectively), whereas the midday shift yielded a higher PDR (44.7%). Interestingly, the authors also found PDR variations over longer time periods: The polyp yield of colonoscopy varied by month, not just among work shifts. The highest PDR was observed in January (46.4%), and the lowest was seen in August (31.7%).
      Although the primary analyses focused on comparing mean PDR among shifts, the authors also report data within shifts. Although there was no hour-by-hour difference observed in shifts 1 and 2, the authors did find hourly differences during the last shift of the day. Whereas polyps were found in 45% of patients who underwent colonoscopy at the beginning of the third shift, this dropped to 34% by the end of the shift (P = .03). Because fatigue is probably worse during the end of the day, these results are consistent with the hypothesis that fatigue might play a role in reduced polyp yield as a work shift progresses. Although the authors conclude that their study “runs counter” to the findings in the Chan et al
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      and Lee et al
      • Lee A.G.N.
      • Iskander J.M.
      • Borg B.B.
      • et al.
      Queue position in the day's endoscopic schedule impacts effectiveness of colonoscopy.
      studies, all 3 studies document decreased polyp yield within a continuous work shift (again, as opposed to measuring between shifts). Although Munson et al did not see this phenomenon in their first and second shifts, which is indeed contrary to the study by Chan et al, they did observe the phenomenon in precisely the shift that seems most eligible for fatigue to creep in—the last shift of the day. And even when they looked among multiple shifts, the authors did find variations as the day progresses, with shift 2 yielding more polyps than shifts 1 and 3. Coupled with data that the month also seems to affect PDR, one could conclude that the Mayo Clinic data strongly support and do not refute the hypothesis that timing matters.
      The authors ultimately concluded that shorter endoscopy shifts might be the way to go—a reasonable conclusion partly supported by these data. However, there is no internal control population here, so it is hard to say. And the study excludes cases with fellows, poor preparation quality, and incomplete examination. Finally, the authors do not report data on adenoma detection—just overall polyp detection. Nonetheless, the study provides some important information about outcomes with a shorter than usual work shift and adds data to the conversation regarding the influence of timing on polyp yield.
      So where does this leave us? First, even if time of day affects polyp (or adenoma) detection rates, the effect is likely to be very small. For example, we found that early morning cases had 0.19 more overall polyps per patient and 0.17 more adenomatous polyps per patient than cases performed later.
      • Chan M.Y.
      • Cohen H.
      • Spiegel B.M.
      Fewer polyps detected by colonoscopy as the day progresses at a Veteran's Administration teaching hospital.
      Because no more than 1 in 20 adenomatous polyps (5%) are thought to progress to colon cancer,
      • Winawer S.
      • Fletcher R.
      • Rex D.
      • et al.
      Colorectal cancer screening and surveillance: clinical guidelines and rationale: update based on new evidence.
      our data indicate that later cases might increase cancer risk by at most 0.9% versus an early morning case (0.05 × 0.17). And because most patients return for surveillance colonoscopies within 3 to 5 years, the attributable risk of late cases is certain to be even smaller. The quality of the operator's technique far outweighs any small risk that time of day might confer. Patients should, first and foremost, seek out good endoscopists and rest assured that time of day is of modest importance.
      But insofar as polyp detection and removal is the mechanism by which colonoscopy reduces cancer risk, these cumulative data introduce the hypothesis that timing might affect cancer outcomes, given enough time and cases. The current study by Munson et al
      • Munson G.W.
      • Harewood G.C.
      • Francis D.L.
      Time of day variation in polyp detection rate for colonoscopies performed on a 3-hour shift schedule.
      is not inconsistent with this possibility, and it provides one solution to help combat the possible effect of fatigue—namely, to set caps on endoscopic work shifts. Even for practices that opt to maintain their traditional half or full-day shifts, endoscopists should still stop and think—“could this be happening with me?” It may not be. In fact, you might get better as the day goes on. But merely having the self-awareness to pose the question may be enough to redouble your efforts the next time you're running late, struggling with a large polyp in the cecum, and finally looking up to find 2 more screening colonoscopies waiting for you at the end of a long and wearisome day. As the Institute of Medicine proclaimed a decade ago, “To err is human.”
      Committee on Quality of Health Care in America, Institute of Medicine
      And endoscopists are human.

      Disclosure

      The author disclosed no financial relationships relevant to this publication.

      Disclaimer

      The opinions and assertions contained herein are the sole views of the author and are not to be construed as official or as reflecting the views of the Department of Veterans Affairs.

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