Evaluating the Optimum Number of Biopsies to Assess Histological Inflammation in Ulcerative Colitis

A Retrospective Cohort Study

Robert Battat; Niels Vande Casteele; Rish K. Pai; Zhongya Wang; Guangyong Zou; John W. D. McDonald; Marjolijn Duijvestein; Jenny Jeyarajah; Claire E. Parker; Tanja Van Viegen; Sigrid A. Nelson; Brigid S. Boland; Siddharth Singh; Parambir S. Dulai; Mark A. Valasek; Brian G. Feagan; Vipul Jairath; William J. Sandborn


Aliment Pharmacol Ther. 2020;52(10):1574-1582. 

In This Article

Abstract and Introduction


Background: The optimal ulcerative colitis biopsy protocol is unclear.

Aim: To evaluate the number of biopsies required to accurately assess microscopic disease activity in ulcerative colitis

Methods: Biopsies from patients with ≥4 rectosigmoid samples, and clinical and endoscopic data, were retrospectively obtained from a prospective biobank. Histology and endoscopic videos were read blindly. A 4-biopsy Robarts Histopathology Index (RHI) reference score, consisting of the worst item-level ratings from four biopsies, was compared to 1-, 2- and 3-biopsy estimates. Agreement was determined using bivariate errors-in-variable regression analysis (acceptance interval: ±8.25). Endoscopic activity and disease location subgroup analyses were also performed.

Results: Forty-six patients had ≥4 rectosigmoid biopsies available (N = 287). The 2-biopsy (tolerance interval: −7.66, 4.79) and 3-biopsy (tolerance interval: −4.86, 3.46) RHI scores demonstrated acceptable agreement with 4-biopsy scores. One-biopsy scores demonstrated unacceptable agreement (tolerance interval: −13.99, 7.78). Mean RHI scores using the 2-, 3- and 4-biopsy approaches were similar (6.1 ± 9.6 P = 0.36; 6.8 ± 10.5, P = 0.7; 7.5 ± 11.2), whereas the 1-biopsy estimate was lower (4.4 ± 8.1, P = 0.06). Histological remission rates were identical for the 2-, 3- and 4-biopsy methods (65.2%, P = 1.0). Subgroup analysis demonstrated that three biopsies were required in patients with endoscopically active disease. Sampling additional colonic locations yielded lower histological remission rates compared to rectosigmoid sampling alone (33.3% vs 61.9%, P = 0.1).

Conclusions: A minimum of two — conservatively, three — biopsies are required to reliably assess disease activity in a single colonic segment using the RHI. Further studies are needed of endoscopically active patients and sampling locations. These results have implications for biopsy strategies in clinical trials and practice.


Ulcerative colitis is a chronic inflammatory disease of the colon characterised by rectal bleeding, diarrhoea and abdominal cramps.[1] Approximately 25% of patients develop severe disease that requires hospitalisation, and nearly 30% undergo colectomy.[2] Additionally, longstanding ulcerative colitis is associated with an increased risk of colorectal cancer.[3]

Although normalisation of clinical symptoms is the historical treatment target for patient management, observational data indicate that assessment of more objective measures of inflammation, such as endoscopic or histological remission, may result in better long-term outcomes.[4–6] In support of this concept, studies have shown that patients who achieve a Mayo Clinic Endoscopic Subscore of 0 or 1 have reduced corticosteroid use and lower rates of hospitalisation and surgery than those with persistent endoscopic inflammation.[7] However, up to one-third of patients who achieve both clinical and endoscopic remission have residual colonic histological activity, which is associated with higher rates of clinical relapse, corticosteroid requirements, colectomy and dysplasia, compared to those in histological remission.[8–12]

These findings have invigorated interest in histology as both an outcome measure in clinical trials and a therapeutic goal in clinical practice. The currently recruiting VERDICT trial aims to evaluate the optimum treatment target (ie clinical symptoms, endoscopic activity, histological activity or biomarkers) in ulcerative colitis (NCT04259138). Other studies have focused on assessing the operating properties of histological indices.[13–15] The Geboes score (GS), an empirically derived seven-item categorical index, has been historically used to classify microscopic disease severity in ulcerative colitis clinical trials; however, it was not specifically designed to measure post-treatment changes.[15,16] Consequently, novel histological indices, including the Robarts Histopathology Index[13] (RHI) and Nancy Histological Index,[15] have been developed and validated to identify therapeutic effects in clinical trials. The RHI is calculated by summing a number of weighted items from the GS to yield a score that ranges from 0 (no disease) to 33 (severe disease).[13,17] The Nancy Histological Index is a 5-point categorical grading system which ranges from Grade 0 (no histologically significant disease) to Grade 4 (severely actively disease).[15,18] The Nancy Histological Index is easily scored, and best suited for use in clinical practice. Conversely, the RHI can be employed as a continuous outcome measure which makes it an efficient tool for detecting treatment differences in small sample sizes.

While histology is routinely assessed in contemporary ulcerative colitis trials, uniform biopsy procurement protocols are lacking. Although the most widely accepted sampling convention in clinical trials is to obtain two biopsies from the most severely affected area of the rectosigmoid colon (typically 15–25 cm from the anal verge), this convention is not based on scientific evidence and the optimum number of biopsies needed to accurately estimate histological disease activity is unknown. Furthermore, it is unclear whether histological activity in the rectosigmoid colon reliably reflects histological disease activity in the right colon among patients with extensive colitis.

Given the increased importance of histological assessment in drug development and its potential value in clinical practice, development of a standardised sampling procedure is a critical research priority. The primary aim of this study was to determine the minimum number of biopsies required to adequately assess histological disease activity in ulcerative colitis patients with varying degrees of endoscopic disease severity. We also sought to determine whether histological activity in the rectosigmoid colon is reflective of that in colonic segments proximal to the splenic flexure in a subgroup of patients with extensive disease. Finally, the construct validity of histological scores from the rectosigmoid colon was also evaluated.