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. 2016 Jun;65(6):963-70.
doi: 10.1136/gutjnl-2014-308411. Epub 2015 Mar 9.

Development and validation of the WASP classification system for optical diagnosis of adenomas, hyperplastic polyps and sessile serrated adenomas/polyps

Joep E G IJspeert  1 , Barbara A J Bastiaansen  1 , Monique E van Leerdam  2 , Gerrit A Meijer  3 , Susanne van Eeden  4 , Silvia Sanduleanu  5 , Erik J Schoon  6 , Tanya M Bisseling  7 , Manon Cw Spaander  8 , Niels van Lelyveld  9 , Marloes Bargeman  10 , Junfeng Wang  11 , Evelien Dekker  1 ; Dutch Workgroup serrAted polypS & Polyposis (WASP)
Collaborators, Affiliations

Development and validation of the WASP classification system for optical diagnosis of adenomas, hyperplastic polyps and sessile serrated adenomas/polyps

Joep E G IJspeert et al. Gut. 2016 Jun.

Abstract

Objective: Accurate endoscopic differentiation would enable to resect and discard small and diminutive colonic lesions, thereby increasing cost-efficiency. Current classification systems based on narrow band imaging (NBI), however, do not include neoplastic sessile serrated adenomas/polyps (SSA/Ps). We aimed to develop and validate a new classification system for endoscopic differentiation of adenomas, hyperplastic polyps and SSA/Ps <10 mm.

Design: We developed the Workgroup serrAted polypS and Polyposis (WASP) classification, combining the NBI International Colorectal Endoscopic classification and criteria for differentiation of SSA/Ps in a stepwise approach. Ten consultant gastroenterologists predicted polyp histology, including levels of confidence, based on the endoscopic aspect of 45 polyps, before and after participation in training in the WASP classification. After 6 months, the same endoscopists predicted polyp histology of a new set of 50 polyps, with a ratio of lesions comparable to daily practice.

Results: The accuracy of optical diagnosis was 0.63 (95% CI 0.54 to 0.71) at baseline, which improved to 0.79 (95% CI 0.72 to 0.86, p<0.001) after training. For polyps diagnosed with high confidence the accuracy was 0.73 (95% CI 0.64 to 0.82), which improved to 0.87 (95% CI 0.80 to 0.95, p<0.01). The accuracy of optical diagnosis after 6 months was 0.76 (95% CI 0.72 to 0.80), increasing to 0.84 (95% CI 0.81 to 0.88) considering high confidence diagnosis. The combined negative predictive value with high confidence of diminutive neoplastic lesions (adenomas and SSA/Ps together) was 0.91 (95% CI 0.83 to 0.96).

Conclusions: We developed and validated the first integrative classification method for endoscopic differentiation of small and diminutive adenomas, hyperplastic polyps and SSA/Ps. In a still image evaluation setting, introduction of the WASP classification significantly improved the accuracy of optical diagnosis overall as well as SSA/P in particular, which proved to be sustainable after 6 months.

Keywords: CANCER PREVENTION; COLONIC POLYPS; COLONOSCOPY; COLORECTAL CANCER; COLORECTAL NEOPLASM.

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