Gastroenterology

Gastroenterology

Volume 128, Issue 3, March 2005, Pages 580-589
Gastroenterology

Clinical-alimentary tract
A prospective assessment of bowel habit in irritable bowel syndrome in women: Defining an alternator

https://doi.org/10.1053/j.gastro.2004.12.006Get rights and content

Background & Aims: Irritable bowel syndrome (IBS) is subtyped as IBS with diarrhea (IBS-D) or IBS with constipation (IBS-C) based on Rome II guidelines. The remaining group is considered as having mixed IBS (IBS-M). There is no standard definition of an alternator (IBS-A), in which bowel habit changes over time. Our aim was to use Rome II criteria to prospectively assess change in bowel habit for more than 1 year to understand IBS-A. Methods: Female patients (n = 317) with IBS entering a National Institutes of Health treatment trial were studied at baseline with questionnaires and 2-week daily diary cards of pain and stool frequency and consistency. Studies were repeated at the end of treatment (3 months) and at four 3-month intervals for one more year. Algorithms to classify subjects into IBS-D, IBS-C, and IBS-M groups used diary card information and modified Rome II definitions. Changes in bowel habit at 3-month intervals were then assessed using these surrogate diary card measures. Results: At baseline, 36% had IBS-D, 31% IBS-M, and 34% IBS-C. Except for stool frequency, there were no differences between groups. While the proportion of subjects in each subgroup remained the same over the year, most individuals (more than 75%) changed to either of the other 2 subtypes at least once. IBS-M was the least stable (50% changed out by 12 weeks). Patients were more likely to transition between IBS-M and IBS-C than between IBS-D and IBS-M. Notably, only 29% switched between the IBS-D and IBS-C subtypes over the year. Conclusions: While the proportion of subjects in each of the IBS subtypes stays the same, individuals commonly transition between subtypes, particularly between IBS-M and IBS-C. We recommend that IBS-A be defined as at least one change between IBS-D and IBS-C by Rome II criteria over a 1-year period.

Section snippets

Study population and protocol

Between 1996 and 2001, female patients between the ages of 18 and 70 years with a functional bowel disorder were enrolled at the University of North Carolina and the University of Toronto to participate in a treatment trial. 4 Before randomization and at the end of the 3-month treatment period either with desipramine or pill placebo or with cognitive-behavioral treatment or education, patients filled out 2 weeks of daily diary cards and then underwent clinical and physiologic assessments. After

Study population

At baseline, there were 317 women with IBS. These patients were subcategorized as having IBS-D (35.6%), IBS-M (neither IBS-D nor IBS-C; 30.6%), or IBS-C (33.8%) using Rome II definitions. The mean age was 38.6 years, 84.9% were white, the mean education level was 14.9 years, and 49.2% were married. There were no demographic differences between subtypes of IBS, except that women with IBS-M were about 2 years younger than women with IBS-D or IBS-C (P = .04).

Baseline comparisons of clinical variables

Table 1 compares the 3 IBS subtypes at

Discussion

IBS is defined as abdominal pain or discomfort associated with altered bowel habit (ie, diarrhea, constipation, or both). 1, 2, 3 In recent years, IBS has been subcategorized into either IBS-D or IBS-C using definitions from the Rome II criteria. 2, 3 The remaining group with Rome II IBS (ie, non–IBS-D, non–IBS-C) is best considered as IBS-M, because this is a heterogeneous group consisting of individuals having symptoms of diarrhea and constipation but not meeting Rome II criteria for either

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    These classifications, however, are subject to recall bias and reflect symptoms over a relatively fixed historical period, and switching from one IBS subtype to another over time has been widely reported.19 In a prospective assessment of abnormal bowel habits of women with IBS, Drossman and colleagues20 found that more than 75% moved to 1 of the other subtypes at least once over a 1-year period. Further complicating the extrapolation of the Rome criteria to routine primary care and GI clinical practice is the fact that IBS exists on a continuum with other disorders of gut-brain interaction, such as chronic idiopathic constipation, functional diarrhea, and functional bloating.21

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Supported by National Institutes of Health grant RO1DK49334 and Novartis Pharmaceuticals.

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