Post written by Marietta Iacucci, MD, PhD, from the NIHR Biomedical Research Centre, Institution of  Translational  Medicine, University of Birmingham, United Kingdom.

Endoscopic scoring of mucosal inflammation and healing is widely used in clinical trials and increasingly in clinical practice. The current endoscopic scores are not precise in assessing minimal inflammatory changes or complete mucosal healing (MH). In most clinical trials, mucosal healing is defined with a Mayo endoscopic score of 0 or 1,  which does not reflect the endoscopic findings of remission in ulcerative colitis (UC) with the current standard of endoscopic resolution. Despite the fact that a Mayo endoscopic score of 1 is considered endoscopic mucosal healing, it is associated with an increased risk of flare up in patients with UC. Both Mayo endoscopic scores 0 and 1 are associated with histologic abnormalities shown by us previously.

An international group of experts aimed to develop a new electronic virtual chromoendoscopy (EVC) score that was more comprehensive in including details of subtle vascular and mucosal changes reflecting chronic and acute inflammation in UC patients using high-definition equipment with EVC. We wanted to better define the characteristics of endoscopic MH in UC patients, PICaSSO (Paddington International virtual ChromoendoScopy ScOre), by determining the intraobserver and interobserver agreement among international experts to assess the correlation with standard endoscopic UC scores and the correlation to several histologic scores.

We have introduced for the first time an integrated EVC score for mucosal and vascular patterns to better assess and grade inflammation and MH in UC. However, the experienced raters performed better in assessing mucosal pattern compared with the vascular pattern. This might be explained by the fact that the detailed electronic vascular endoscopic score is a newly developing concept even for experienced observers. The classical description of loss of vascular pattern in UC, no longer seen by high-definition endoscopy, has been revised by incorporating the fine distortions in vascular pattern seen with EVC. The intra- and inter-observer variability of mucosal, vascular, and overall PICaSSO scores between the raters were very good. The overall PICaSSO score was good in correlating with the current endoscopic and histological scores in use. This score can now be used to study the effect of treatments and clinical outcomes in prospective studies.

Figure 4. Accuracy of the PICaSSO to assess mucosal healing and inflammation in ulcerative colitis. RHI, Robarts Histological Index; ECAP, extent, chronicity, activity, plus.

A limitation to this original study is that all participants were dedicated endoscopy experts; however, we have further showed that the PICaSSO achieves good inter-rater reliability post-training, across all levels of endoscopy experience with performance accuracy that is sustainable over time. PICaSSO provides the most accurate discrimination between quiescent and mild histological disease activity, compared to the Mayo score and UCEIS. We are conducting a real-life, multi-center study which will address further outcome data associated with endoscopic findings of the Picasso score and the reproducibility on multiple endoscopic platforms.

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