Inclusion and exclusion criteria of importance in irritable bowel syndrome trials

New clinical method for distinguishing D-IBS from other gastrointestinal conditions causing diarrhea: the LA/IBS diagnostic strategy

Modern methods of diagnosing diarrhea-predominant irritable bowel syndrome (D-IBS) require a "diagnosis of exclusion" approach. In this study we aim to test the diagnostic ability of using the fluctuation of frequency and consistency of bowel patterns in IBS to discriminate it from other causes of diarrhea. Eligible subjects were asked to complete a questionnaire on the changes in form and frequency of bowel habits by time. The primary endpoint was to evaluate the diagnostic effectiveness of having irregularly irregular bowel function and form as more characteristic of IBS versus non-IBS causes. Patients were prospectively recruited from a tertiary care GI clinic. Subjects had to have diarrhea as their primary complaint. In the case of IBS, D-IBS subjects were recruited. Subjects with celiac disease, Crohn's and ulcerative colitis were recruited for comparison and were categorically called "non-IBS." Non-IBS subjects could not have a recent history of blood in stool or a history of bowel surgery, fistulae or narcotic use. Sixty-two IBS and 37 non-IBS subjects were recruited. Among the 62 IBS subjects, 49 (79%) stated that their bowel habits varied in form and frequency on a daily basis compared to 35% in non-IBS subjects (OR = 8.9, CI = 3.5-22.5, P < 0.00001). When subjects were compared by the number of different stool forms they had witnessed in the prior week, IBS subjects noted 3.58 +/- 0.19 types and non-IBS reported 2.35 +/- 0.16 (P < 0.00001). Using > or = 3 stool forms per week as a method of discriminating IBS from non-IBS, 50 out of 62 subjects with IBS (81%) reported this greater number of forms compared to 15 out of 37 (41%) non-IBS subjects (sensitivity = 0.81; specificity = 0.60). The use of this simple tool that identifies an irregularly irregular bowel form and function is successful in separating D-IBS from non-IBS subjects.

Extra-intestinal manifestations associated with irritable bowel syndrome: a twin study

BACKGROUND

Little is known about the role of genetic and environmental factors in irritable bowel syndrome. Various extra-intestinal manifestations are more prevalent in cases than in controls. Genetic effects may be important in the liability to develop functional bowel disorders.

AIMS

To evaluate the associations of irritable bowel syndrome with several disorders co-morbid with the condition, using both a case-control design and a co-twin control design.

METHODS

A sample of 850 Swedish twin pairs, aged 18-85 years, was contacted for a telephone interview. Through a diagnostic algorithm, 72 unrelated cases of irritable bowel syndrome and 216 age- and gender-matched controls were identified. Fifty-eight twin pairs discordant for irritable bowel syndrome were evaluated in co-twin analyses.

RESULTS

Renal problems (odds ratio (OR)=3.3; confidence interval (CI), 1.3-8.2), obesity (OR=2.6; CI, 1.0-6.4), underweight in the past (OR=2.4; CI, 1.1-6.4), gluten intolerance (OR=9.0; CI, 1.4-60.1), rheumatoid arthritis (OR=3.2; CI, 1.1-9.4) and poor self-rated health (OR=1.8; CI, 1.0-3.2) were significantly associated with irritable bowel syndrome. In the co-twin analyses, the only factors maintaining significance were renal and recurrent urinary tract problems.

CONCLUSIONS

The association between irritable bowel syndrome and renal and urinary tract problems does not reflect a genetic or familial mediation. Eating disorders in childhood represent a familial-environmental influence on irritable bowel syndrome, whereas the association with rheumatoid arthritis and perhaps gluten intolerance probably reflects genetic mediation.