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Paris classification of colonic polyps using CT colonography: prospective cohort study of interobserver variation

  • Gastrointestinal
  • Published:
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Abstract

Background

The Paris classification categorises colorectal polyp morphology. Interobserver agreement for Paris classification has been assessed at optical colonoscopy (OC) but not CT colonography (CTC). We aimed to determine the following: (1) interobserver agreement for the Paris classification using CTC between radiologists; (2) if radiologist experience influenced classification, gross polyp morphology, or polyp size; and (3) the extent to which radiologist classifications agreed with (a) colonoscopy and (b) a combined reference standard.

Methods

Following ethical approval for this non-randomised prospective cohort study, seven radiologists from three hospitals classified 52 colonic polyps using the Paris system. We calculated interobserver agreement using Fleiss kappa and mean pairwise agreement (MPA). Absolute agreement was calculated between radiologists; between CTC and OC; and between CTC and a combined reference standard using all available imaging, colonoscopic, and histopathological data.

Results

Overall interobserver agreement between the seven readers was fair (Fleiss kappa 0.33; 95% CI 0.30–0.37; MPA 49.7%). Readers with < 1500 CTC experience had higher interobserver agreement (0.42 (95% CI 0.35–0.48) vs. 0.33 (95% CI 0.25–0.42)) and MPA (69.2% vs 50.6%) than readers with ≥ 1500 experience. There was substantial overall agreement for flat vs protuberant polyps (0.62 (95% CI 0.56–0.68)) with a MPA of 87.9%. Agreement between CTC and OC classifications was only 44%, and CTC agreement with the combined reference standard was 56%.

Conclusion

Radiologist agreement when using the Paris classification at CT colonography is low, and radiologist classification agrees poorly with colonoscopy. Using the full Paris classification in routine CTC reporting is of questionable value.

Clinical relevance statement

Interobserver agreement for radiologists using the Paris classification to categorise colorectal polyp morphology is only fair; routine use of the full Paris classification at CT colonography is questionable.

Key Points

• Overall interobserver agreement for the Paris classification at CT colonography (CTC) was only fair, and lower than for colonoscopy.

• Agreement was higher for radiologists with < 1500 CTC experience and for larger polyps. There was substantial agreement when classifying polyps as protuberant vs flat.

• Agreement between CTC and colonoscopic polyp classification was low (44%).

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Abbreviations

CI:

Confidence interval

CRC:

Colorectal cancer

CTC:

CT colonography

MPA:

Mean pairwise agreement

PACS:

Picture archiving and communication system

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Funding

This study has received funding from the British Society of Gastrointestinal and Abdominal Radiology (BSGAR) via its Education Bursary scheme.

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Authors and Affiliations

  1. Nottingham University Hospitals NHS Trust, Nottingham, UK

    Anmol Gangi-Burton

  2. University College London Hospitals NHS Foundation Trust, London, UK

    Andrew A. Plumb & Anisha Patel

  3. Addenbrooke’s Hospital, Cambridge, UK

    Katja N. De Paepe, Edmund M. Godfrey & Samir Khwaja

  4. Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA

    Katja N. De Paepe

  5. Centre for Medical Imaging, University College London, London, UK

    Steve Halligan & Stuart Taylor

  6. Queen Alexandra Hospital, Portsmouth, UK

    Antony Higginson

Authors
  1. Anmol Gangi-Burton
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  2. Andrew A. Plumb
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  3. Katja N. De Paepe
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  4. Edmund M. Godfrey
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  5. Steve Halligan
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  7. Samir Khwaja
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  8. Anisha Patel
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  9. Stuart Taylor
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Corresponding author

Correspondence to Andrew A. Plumb.

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Guarantor

The scientific guarantor of this publication is Dr Andrew Plumb.

Conflict of interest

Andrew Plumb is a member of the European Radiology Editorial Board. They have not taken part in the review or selection process of this article.

The other authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.

Statistics and biometry

One of the authors has significant statistical expertise (Andrew Plumb).

Informed consent

Written informed consent was waived by the Institutional Review Board.

Ethical approval

Institutional Review Board approval was obtained.

Study subjects or cohorts overlap

Some study subjects or cohorts have been previously reported in:

Obaro AE, Plumb AA, Halligan S et al (2022) Colorectal cancer: performance and evaluation for CT colonography screening- a multicenter cluster-randomized controlled trial. Radiology 303(2):361–370.

Methodology

• prospective

• observational

• multicentre study

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Gangi-Burton, A., Plumb, A.A., De Paepe, K.N. et al. Paris classification of colonic polyps using CT colonography: prospective cohort study of interobserver variation. Eur Radiol (2024). https://doi.org/10.1007/s00330-024-10631-9

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  • DOI: https://doi.org/10.1007/s00330-024-10631-9

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