Measuring symptoms in the irritable bowel syndrome: development of a framework for clinical trials.

BACKGROUND: There is uncertainty about how to measure patient-reported outcomes (PROs) in IBS. The Food and Drug Administration (FDA) emphasizes that PROs must be couched in a conceptual framework, yet existing IBS PROs were not based on such a framework. AIM: To perform qualitative analyses to inform a new conceptual framework for IBS symptoms.
METHODS: Following FDA guidance, we searched the literature for extant IBS questionnaires. We then performed interviews in IBS patients to learn about the illness experience in their own words. We cultivated vocabulary to inform a conceptual framework depicted with domains, sub-domains, and item categories, per FDA guidance.
RESULTS: We identified 13 questionnaires with items encompassing 18 symptoms. We recruited 123 IBS patients for cognitive interviews. Major themes included: pain and discomfort are different - asking about discomfort is nonspecific and should be avoided in future PROs; bowel urgency is multifaceted - PROs should measure bowel immediacy, controllability, and predictability; and PROs should divide bloating into how it feels vs. how it looks. Symptom experience may be determined by 35-item categories within five domains: (i) pain; (ii) gas/bloat; (iii) diarrhoea; (iv) constipation; and (v) extraintestinal symptoms.
CONCLUSIONS: We applied FDA guidance to develop a framework that can serve as the foundation for developing a PRO for IBS clinical trials.