Irritable bowel syndrome clinical trials: getting the IBS Severity Scoring System responder rate right

Henning Sommermeyer; Krzysztof Chmielowiec; Paulina Wojtyła-Buciora; Malgorzata Bernatek; Pawel Olszewski; Zygmunt Kopczynski; Jacek Piatek

doi:10.5114/pg.2025.156735

eISSN: 1897-4317
ISSN: 1895-5770

Gastroenterology Review/Przegląd Gastroenterologiczny

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abstract:

Original paper

Irritable bowel syndrome clinical trials: getting the IBS Severity Scoring System responder rate right

Henning Sommermeyer

¹

,

Krzysztof Chmielowiec

²

,

Paulina Wojtyła-Buciora

¹

,

Malgorzata Bernatek

¹

,

Pawel Olszewski

¹

,

Zygmunt Kopczynski

¹

,

Jacek Piatek

¹

Department of Medicine and Health Sciences, Calisia University, Kalisz, Poland
Department of Hygiene and Epidemiology, Collegium Medicum, University of Zielona Góra, Poland

Gastroenterology Review

DOI: https://doi.org/10.5114/pg.2025.156735

Online publish date: 2025/12/07

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Introduction
The Irritable Bowel Syndrome Severity Scoring System (IBS-SSS) is frequently used to characterize treatment effects in IBS patients. Calculation of a responder rate using IBS-SSS data commonly uses a cut-off value of –50 points.

Aim
To analyze data from a recently published IBS trial to evaluate whether this cut-off value is appropriate or needs to be revised.

Material and methods
Data from 201 patients were used to establish a receiver operating characteristic (ROC) curve for IBS-SSS change data using IBS-Adequate Relief scale data as a binary classifier. The area under the curve (AUC) and its 95% CI for the ROC were determined. Curves plotting accuracy rates and Youden’s J index values against changes on the IBS-SSS used as cut-off values were employed to determine an optimal cut-off value

Results
The AUC of the ROC curve was 0.9738 (95% CI from 0.9565 to 0.9912). The curve of accuracy rates had two maxima (–122 and –133 points), while that of the Youden’s J index values had only one maximum at –122 points, considered to be the optimal cut-off value.

Conclusions
The frequently used –50 points cut-off value might not be optimal for determining clinically meaningful responder rates from IBS-SSS measurements. At least for the IBS-SSS data analyzed in the present study, a change of –122 points appears to be more appropriate. Interpretation of IBS-SSS responder rates from past or future clinical trials should carefully check for the cut-off values applied for their calculation.

keywords:

Irritable bowel syndrome clinical trials: getting the IBS Severity Scoring System responder rate right

Henning Sommermeyer 1 , Krzysztof Chmielowiec 2 , Paulina Wojtyła-Buciora 1 , Malgorzata Bernatek 1 , Pawel Olszewski 1 , Zygmunt Kopczynski 1 , Jacek Piatek 1

irritable bowel syndrome, IBS Adequate Relief scale, IBS Severity Scoring System, receiver operating characteristics, ViIBS trial

Henning Sommermeyer

¹

,

Krzysztof Chmielowiec

²

,

Paulina Wojtyła-Buciora

¹

,

Malgorzata Bernatek

¹

,

Pawel Olszewski

¹

,

Zygmunt Kopczynski

¹

,

Jacek Piatek

¹