Article Text

Download PDFPDF

Original article
Narrow band imaging optical diagnosis of small colorectal polyps in routine clinical practice: the Detect Inspect Characterise Resect and Discard 2 (DISCARD 2) study
  1. Colin J Rees1,2,3,
  2. Praveen T Rajasekhar1,3,
  3. Ana Wilson4,
  4. Helen Close5,
  5. Matthew D Rutter2,3,6,
  6. Brian P Saunders4,
  7. James E East7,
  8. Rebecca Maier5,
  9. Morgan Moorghen4,
  10. Usman Muhammad5,
  11. Helen Hancock5,
  12. Anthoor Jayaprakash8,
  13. Chris MacDonald9,
  14. Arvind Ramadas10,
  15. Anjan Dhar11,
  16. James M Mason12
    1. 1Department of Gastroenterology, South Tyneside NHS Foundation Trust, South Shields, UK
    2. 2School of Medicine, Pharmacy and Health, Durham University, Durham, UK
    3. 3Northern Region Endoscopy Group, UK
    4. 4St Mark's Hospital and Academic Institute, London North West Healthcare NHS Trust, Imperial College London, London, UK
    5. 5Durham Clinical Trials Unit, School of Medicine Pharmacy & Health, Durham University, Stockton-on-Tees, UK
    6. 6Department of Gastroenterology, North Tees & Hartlepool NHS Foundation Trust, Stockton-on-Tees, UK
    7. 7Translational Gastroenterology Unit, John Radcliffe Hospital, University of Oxford, Oxford, UK
    8. 8Department of Gastroenterology, Northumbria Healthcare NHS Foundation Trust, Newcastle upon Tyne, UK
    9. 9Department of Gastroenterology, North Cumbria University Hospitals NHS Trust, Carlisle, UK
    10. 10Department of Gastroenterology, South Tees Hospitals NHS Foundation Trust, Middlesborough, UK
    11. 11Department of Gastroenterology, County Durham & Darlington NHS Foundation Trust, Darlington, UK
    12. 12Warwick Medical School, University of Warwick, Coventry, UK
    1. Correspondence to Professor Colin J Rees, Department of Gastroenterology, South Tyneside District Hospital, South Shields NE34 0PL, UK; Colin.Rees{at}


    Background 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.

    Methods 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.

    Findings 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.

    Interpretation 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.

    Trial registration number The study was registered with (NCT01603927).


    This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:

    View Full Text

    Statistics from

    Request Permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.