title: Narrow band imaging optical diagnosis of small colorectal polyps in routine clinical practice: the Detect Inspect Characterise Resect and Discard 2 (DISCARD 2) study.
abstract: Accurate optical characterisation and removal of small adenomas (<10 mm) at colonoscopy would allow hyperplastic polyps to be left in situ and surveillance intervals to be determined without the need for histopathology. Although accurate in specialist practice the performance of narrow band imaging (NBI), colonoscopy in routine clinical practice is poorly understood.
  
  
  
  NBI-assisted optical diagnosis was compared with reference standard histopathological findings in a prospective, blinded study, which recruited adults undergoing routine colonoscopy in six general hospitals in the UK. Participating colonoscopists (N=28) were trained using the NBI International Colorectal Endoscopic (NICE) classification (relating to colour, vessel structure and surface pattern). By comparing the optical and histological findings in patients with only small polyps, test sensitivity was determined at the patient level using two thresholds: presence of adenoma and need for surveillance. Accuracy of identifying adenomatous polyps <10 mm was compared at the polyp level using hierarchical models, allowing determinants of accuracy to be explored.
  
  
  
  Of 1688 patients recruited, 722 (42.8%) had polyps <10 mm with 567 (78.5%) having only polyps <10 mm. Test sensitivity (presence of adenoma, N=499 patients) by NBI optical diagnosis was 83.4% (95% CI 79.6% to 86.9%), significantly less than the 95% sensitivity (p<0.001) this study was powered to detect. Test sensitivity (need for surveillance) was 73.0% (95% CI 66.5% to 79.9%). Analysed at the polyp level, test sensitivity (presence of adenoma, N=1620 polyps) was 76.1% (95% CI 72.8% to 79.1%). In fully adjusted analyses, test sensitivity was 99.4% (95% CI 98.2% to 99.8%) if two or more NICE adenoma characteristics were identified. Neither colonoscopist expertise, confidence in diagnosis nor use of high definition colonoscopy independently improved test accuracy.
  
  
  
  This large multicentre study demonstrates that NBI optical diagnosis cannot currently be recommended for application in routine clinical practice. Further work is required to evaluate whether variation in test accuracy is related to polyp characteristics or colonoscopist training.
  
  
  
  The study was registered with clinicaltrials.gov (NCT01603927).
authors.affiliation: Department of Gastroenterology, South Tyneside NHS Foundation Trust, South Shields, UK.|School of Medicine, Pharmacy and Health, Durham University, Durham, UK.|Northern Region Endoscopy Group, UK.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Rees
authors.affiliation: Department of Gastroenterology, South Tyneside NHS Foundation Trust, South Shields, UK.|Northern Region Endoscopy Group, UK.
authors.forename: Praveen T
authors.initials: PT
authors.lastname: Rajasekhar
authors.affiliation: St Mark's Hospital and Academic Institute, London North West Healthcare NHS Trust, Imperial College London, London, UK.
authors.forename: Ana
authors.initials: A
authors.lastname: Wilson
authors.affiliation: Durham Clinical Trials Unit, School of Medicine Pharmacy & Health, Durham University, Stockton-on-Tees, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Close
authors.affiliation: School of Medicine, Pharmacy and Health, Durham University, Durham, UK.|Northern Region Endoscopy Group, UK.|Department of Gastroenterology, North Tees & Hartlepool NHS Foundation Trust, Stockton-on-Tees, UK.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Rutter
authors.affiliation: St Mark's Hospital and Academic Institute, London North West Healthcare NHS Trust, Imperial College London, London, UK.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Saunders
authors.affiliation: Translational Gastroenterology Unit, John Radcliffe Hospital, University of Oxford, Oxford, UK.
authors.forename: James E
authors.initials: JE
authors.lastname: East
authors.affiliation: Durham Clinical Trials Unit, School of Medicine Pharmacy & Health, Durham University, Stockton-on-Tees, UK.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Maier
authors.affiliation: St Mark's Hospital and Academic Institute, London North West Healthcare NHS Trust, Imperial College London, London, UK.
authors.forename: Morgan
authors.initials: M
authors.lastname: Moorghen
authors.affiliation: Durham Clinical Trials Unit, School of Medicine Pharmacy & Health, Durham University, Stockton-on-Tees, UK.
authors.forename: Usman
authors.initials: U
authors.lastname: Muhammad
authors.affiliation: Durham Clinical Trials Unit, School of Medicine Pharmacy & Health, Durham University, Stockton-on-Tees, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Hancock
authors.affiliation: Department of Gastroenterology, Northumbria Healthcare NHS Foundation Trust, Newcastle upon Tyne, UK.
authors.forename: Anthoor
authors.initials: A
authors.lastname: Jayaprakash
authors.affiliation: Department of Gastroenterology, North Cumbria University Hospitals NHS Trust, Carlisle, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: MacDonald
authors.affiliation: Department of Gastroenterology, South Tees Hospitals NHS Foundation Trust, Middlesborough, UK.
authors.forename: Arvind
authors.initials: A
authors.lastname: Ramadas
authors.affiliation: Department of Gastroenterology, County Durham & Darlington NHS Foundation Trust, Darlington, UK.
authors.forename: Anjan
authors.initials: A
authors.lastname: Dhar
authors.affiliation: Warwick Medical School, University of Warwick, Coventry, UK.
authors.forename: James M
authors.initials: JM
authors.lastname: Mason
mesh_terms: D000236:Adenoma / Q000000981:diagnostic imaging* / Q000473:pathology; D000368:Aged; D002983:Clinical Competence; D003111:Colonic Polyps / Q000000981:diagnostic imaging* / Q000473:pathology; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D062048:Narrow Band Imaging; D015588:Observer Variation; D011159:Population Surveillance; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors
keywords: COLONIC NEOPLASMS; COLONOSCOPY; COLORECTAL ADENOMAS; ENDOSCOPY