Assessment of the multiple components of the variability in the adenoma detection rate in sigmoidoscopy screening, and lessons for training[*]

Background and study aims: The determinants of the observed variability of adenoma detection rate (ADR) in endoscopy screening have not yet been fully explained.

Patients and methods: Between November 1999 and November 2006 13 764 people (7094 men, 6670 women; age range 55 – 64) underwent screening flexible sigmoidoscopy at five hospital endoscopy units in Turin. To study the determinants of the ADR for distal adenomas, accounting for patient, examiner, and hospital characteristics, we applied a multivariate multilevel regression model.

Results: Average ADRs for all adenomas and for advanced adenomas (size ≥ 10 mm, villous component > 20 %, high grade dysplasia) were 13.5 % (range 5.2 % – 25.0 %) and 6.4 % (3.1 % – 10.7 %) for men, and 8.0 % (2.5 % – 14.0 %) and 3.7 % (0.2 % – 7.4 %) for women. In multivariate analysis, increased ADR of advanced adenomas was associated with male gender (odds ratio [OR] 1.78, 95 %CI 1.49 – 2.11), self-report of one first-degree relative with colorectal cancer (CRC) (1.44, 1.11 – 1.86), or of recent-onset rectal bleeding (1.73, 1.24 – 2.40). Adjusting for these variables, a significantly lower ADR was found for endoscopists with either a lower rate of incomplete sigmoidoscopy (< 9 %; OR 0.59, 95 %CI 0.41 – 0.87) or a higher rate (> 12 %; 0.64, 0.45 – 0.91), or with low activity volume (< 85 sigmoidoscopies/year; 0.66, 0.50 – 0.86). Residual variability explained by the endoscopy center effect was about 1 % and statistically significant.

Conclusions: Endoscopist performance in flexible sigmoidoscopy CRC screening is highly variable. Low volume of screening activity independently predicts lower ADR, suggesting that operators devoting more time to screening sigmoidoscopy may perform better. Variability among pathologists in adenoma classification might explain part of the residual variability across endoscopy units.

1 A preliminary version of this study was presented at DDW 2008, San Diego.

References

• 1 US Preventive Service Task Force . Screening for colorectal cancer: US Preventive Service Task Force Recommendation Statement.  Ann Intern Med. 2008;  149 627-637
• 2 Zorzi M, Fedato C, Naldoni C, Sassatelli R. et al . Screening for colorectal cancer in Italy: 2007 survey.  Epidemiol Prev.. 2009;  33 Suppl 2 57-74
• 3 Hoff G, Grotmol T, Skovlund E. et al . Risk of colorectal cancer seven years after flexible sigmoidoscopy screening: randomised controlled trial.  BMJ. 2009;  338 b1846
• 4 Hol L, van Leerdam M E, van Ballegooijen M. et al . Screening for colorectal cancer: randomised trial comparing guaiac-based and immunochemical faecal occult blood testing and flexible sigmoidoscopy.  Gut. 2010;  59 62-68
• 5 Viiala C H, Olynyk J K. Outcomes after 10 years of a community-based flexible sigmoidoscopy screening program for colorectal carcinoma.  Med J Aust. 2007;  187 274-277
• 6 Rex D K, Cutler C S, Lemmel G T. et al . Colonoscopic miss rates of adenomas determined by back-to-back colonoscopies.  Gastroenterology. 1997;  112 24-28
• 7 Levin T R, Farraye F A, Schoen R E. et al . Quality in the technical performance of screening flexible sigmoidoscopy: recommendations of an international multisociety task group.  Gut. 2005;  54 807-813
• 8 Schoenfield P, Lipscomb S, Crook J. et al . Accuracy of polyp detection by gastroenterologists and nurse endoscopists during flexible sigmoidoscopy: a randomized trial.  Gastroenterology. 1999;  117 312-318
• 9 Bretthauer M, Skovlund E, Grotmol T. et al . Inter-endoscopist variation in polyp and neoplasia pick-up rates in flexible sigmoidoscopy screening for colorectal cancer.  Scand J Gastroenterol. 2003;  38 1268-1274
• 10 Atkin W, Rogers P, Cardwell C. et al . Wide variation in adenoma detection rates at screening flexible sigmoidoscopy.  Gastroenterology. 2004;  126 1247-1256
• 11 Pinsky P F, Schoen R E, Weissfeld J L. et al . Variability in flexible sigmoidoscopy performance among examiners in a screening trial.  Gastroenterology. 2005;  3 792-797
• 12 Rex D K. Colonoscopic withdrawal technique is associated with adenoma miss rate.  Gastrointest Endosc. 2000;  51 33-36
• 13 Barclay R L, Vicari J J, Doughty A S. et al . Colonoscopic withdrawal times and adenoma detection during screening colonoscopy.  N Engl J Med. 2006;  355 2533-2541
• 14 Segnan N, Senore C, Andreoni B. et al . Randomized trial of different screening strategies for colorectal cancer: patient response and detection rates.  J Natl Cancer Inst. 2005;  97 347-357
• 15 Segnan N, Senore C, Andreoni B. et al . Comparing attendance and detection rate of colonoscopy with sigmoidoscopy and FIT for colorectal cancer screening.  Gastroenterology. 2007;  132 2304-2312
• 16 Jass J R, Sobin L H. Histological typing of intestinal tumors. 2nd edn. New York; Springer 1989
• 17 Carey R G. Improving healthcare with control charts: Basic and advanced SPC methods and case studies. Milwaukee; Quality Press 2003
• 18 Goldstein H. Multilevel statistical models. 3rd edn. New York; Oxford University Press 2003
• 19 StataCorp LP .Stata Statistical Software: release SE 9.2. Stata Corporation, College Station. Texas; 2007
• 20 Goldstein H, Spiegelhalter D J. League tables and their limitations: statistical issues in comparisons of institutional performance.  J R Stat Soc. 1996;  Series A, 159 385-443
• 21 Goldstein H, Thomas S. Using examination results as indicators of school and college performance.  J R Stat Soc. 1996;  Series A, 159 149-163
• 22 Winawer S J, Zauber A G, Gerdes H. et al . Risk of colorectal cancer in the families of patients with adenomatous polyps. National Polyp Study Workgroup.  N Engl J Med. 1996;  334 82-87
• 23 Ferraris R, Senore C, Fracchia M. et al . Predictive value of rectal bleeding for distal colonic neoplastic lesions in a screened population.  Eur J Cancer. 2004;  40 245-52
• 24 Thomas-Gibson S, Rogers P, Cooper S. et al . Judgement of the quality of bowel preparation at screening flexible sigmoidoscopy is associated with variability in adenoma detection rate.  Endoscopy. 2006;  38 456-460
• 25 Simmons D T, Harewood G C, Baron T H. et al . Impact of endoscopist withdrawal speed on polyp yield: implications for optimal colonoscopy withdrawal time.  Aliment Pharmacol Ther. 2006;  24 965-971
• 26 Woolfson I K, Eckholdt G J, Wetzel R. et al . Usefulness of performing colonoscopy one year after endoscopic polypectomy.  Dis Colon Rectum. 1990;  33 389-393
• 27 Sanaka M R, Deepinder F, Thota P N. et al . Adenomas are detected more often in morning than in afternoon colonoscopy.  Am J Gastroenterol. 2009;  104 1659-1664
• 28 Yoon H, Martin A, Benamouzig R. et al . Inter-observer agreement on histological diagnosis of colorectal polyps: the APACC study.  Gastroenterol Clin Biol. 2002;  26 220-224
• 29 Costantini M, Sciallero S, Giannini A. et al . Interobserver agreement in the histologic diagnosis of colorectal polyps. The experience of the multicenter adenoma colorectal study (SMAC).  J Clin Epidemiol. 2003;  56 209-214
• 30 Atkin W S, Morson B C, Cuzick J. Long-term risk of colorectal cancer after excision of rectosigmoid adenomas.  N Engl J Med. 1992;  326 658-662
• 31 Imperiale T F, Wagner D R/ADR, Lin C Y. et al . Risk of advanced proximal neoplasms in asymptomatic adults according to the distal colorectal findings.  N Engl J Med. 2000;  343 169-174

1 A preliminary version of this study was presented at DDW 2008, San Diego.