A prospective assessment of bowel habit in irritable bowel syndrome in women: defining an alternator.
OBJECTIVE
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.
Drossman
Douglas A
DA
UNC Center for Functional GI and Motility Disorders, University of North Carolina at Chapel Hill, Room 1110 Burnett-Womack CB#7080, Chapel Hill, North Carolina 27599-7080, USA.
Morris
Carolyn B
CB
Hu
Yuming
Y
Toner
Brenda B
BB
Diamant
Nicholas
N
Leserman
Jane
J
Shetzline
Michael
M
Dalton
Christine
C
Bangdiwala
Shrikant I
SI
D000328:Adult; D000368:Aged; D003248:Constipation / Q000209:etiology; D003672:Defecation; D003967:Diarrhea / Q000209:etiology; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000145:classification* / Q000150:complications / Q000503:physiopathology*; D008499:Medical Records; D008875:Middle Aged; D010146:Pain / Q000503:physiopathology; D011446:Prospective Studies; D013997:Time Factors