Characterization of the Alternating Bowel Habit Subtype in Patients With Irritable Bowel Syndrome

Kirsten Tillisch, M.D.; Jennifer S. Labus, Ph.D.; Bruce D. Naliboff, Ph.D.; Roger Bolus, Ph.D.; Michael Shetzline, M.D.; Emeran A. Mayer, M.D.; Lin Chang, M.D.


Am J Gastroenterol. 2005;100(4):896-904. 

In This Article

Abstract and Introduction

Background: Due to a wide range of symptom patterns, patients with irritable bowel syndrome (IBS) are often subgrouped by bowel habit. However, the IBS subgroup with alternating bowel habits (IBS-A) has been poorly characterized.
Objectives: (i) To determine a set of bowel habit symptom criteria, which most specifically identifies IBS patients with an alternating bowel habit, (ii) to describe IBS-A bowel symptom patterns, and (iii) to compare clinical characteristics among IBS-A, constipation-predominant (IBS-C), and diarrhea-predominant IBS (IBS-D).
Methods: One thousand one hundred and two Rome I positive IBS patients were analyzed. Three sets of potential criteria for IBS-A were developed and compared by multirater Kappa test. Gastrointestinal, psychological, extraintestinal symptoms, and health-related quality of life were compared in IBS-A, IBS-C, and IBS-D using χ2 test and analysis of variance (ANOVA).
Results: Stool consistency was determined to be the most specific criteria for alternating bowel habits. IBS-A patients reported rapid fluctuations in bowel habits with short symptom flares and remissions. There was a greater prevalence of psychological and extraintestinal symptoms in the IBS-A subgroup compared to IBS-C and IBS-D. No differences were seen between bowel habit subtypes in health-related quality of life.
Conclusions: IBS-A patients have rapidly fluctuating symptoms and increased psychological comorbidity, which should be taken into account for clinical practice and clinical trials.

Irritable bowel syndrome (IBS) is a chronic, functional disorder of the gastrointestinal (GI) tract affecting 9.4-21.8% of the U.S. population.[1] Affected individuals have chronic or recurrent abdominal pain or discomfort associated with an altered pattern of defecation. Patterns of disturbed defecation may range from diarrhea to constipation to an alternation between the two. Patients are often subclassified by their predominant bowel habit, that is, diarrhea-predominant (IBS-D), constipation-predominant (IBS-C), or alternating diarrhea and constipation (IBS-A). While it is believed that patients with IBS share underlying pathophysiologic features regardless of bowel habit, several differences in perception, autonomic function, and symptom characteristics between IBS-D and IBS-C patients have been described.[2,3,4,5] Studies have typically focused on the IBS-D and IBS-C subgroups, most likely due to the fact that their symptoms are easier to differentiate than those of IBS-A. IBS patients with an alternating bowel habit pattern present a unique clinical challenge and many of the IBS medications being studied affect either diarrhea or constipation thus may not be appropriate for IBS-A patients.[6,7]

The most recent symptom-based diagnostic criteria for IBS (Rome II) have recommended the use of specific GI symptoms to classify patients into those with IBS-D and IBS-C.[8] However, these suggested subgrouping criteria were determined by expert opinion, and were not evidence-based. No criteria were suggested for the IBS-A subgroup, and the determination of clinical symptoms on which to base this classification has been challenging. Despite this relative lack of attention, the IBS-A subgroup appears to make up between 19% and 63% of IBS patients.[9,10,11]

Traditional management of IBS patients has routinely included the use of fiber supplementation and laxatives to treat symptoms of constipation and antidiarrheal agents to treat symptoms of diarrhea. This approach may be useful in IBS-A patients with sustained periods of diarrhea or constipation but may exacerbate symptoms in those with rapidly alternating bowel habits. The temporal pattern of bowel habit alternation in this subgroup has not previously been established. Newer therapies used for the management of IBS symptoms, such as tegaserod for IBS-C[7] and alosetron for IBS-D,[6] are targeted at specific bowel habit patterns and the efficacy of these pharmacologic agents in IBS-A patients has not been well studied. For the purposes of clinical research studies and patient management it is important to find a simple method to identify patients who have alternating bowel habits as their predominant pattern.

A variety of criteria have been used to describe the IBS-A subgroup.[9,10,12,13,14,15] However, the rationale for the criteria in each study is often not stated. Various permutations of the Rome II criteria are the most common method used to define the IBS-A subgroup ( e.g., those not fitting either the definitions of IBS-C or IBS-D), though the criteria were not designed for this purpose. The aims of this study are: (i) to determine a set of bowel habit symptom criteria, which is most specific for IBS patients with alternating bowel habits; (ii) to examine clinical characteristics of the IBS-A subgroup, including symptom severity, fluctuations of alternating bowel habits, duration of symptom exacerbations, and remissions, psychological symptoms, extraintestinal symptoms, and health-related quality of life (HRQoL); and (iii) to compare the IBS-A subgroup to the IBS-C and IBS-D subgroups.


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