Responsiveness to Change and Minimally Important Differences of the Patient-Reported Outcomes Measurement Information System Gastrointestinal Symptoms Scales.

BACKGROUND: The NIH-sponsored Patient-Reported Outcomes Measurement Information System (PROMIS) Gastrointestinal (GI) Symptoms scales were developed to assess patients' GI symptoms in clinical settings. AIMS: To assess responsiveness to change and provide minimally important difference (MID) estimates for the PROMIS GI Symptoms scales. METHODS: A sample of 256 GI outpatients self-administered the eight PROMIS GI Symptoms scales (gastroesophageal reflux, disrupted swallowing, diarrhea, bowel incontinence/soilage, nausea and vomiting, constipation, belly pain, and gas/bloating/flatulence) at two visits. Patient self-reported and physician-reported assessments of the subjects' overall GI condition were employed as change anchors. In addition, we prospectively assessed change at both visits using a GI-symptom anchor, the Gastrointestinal Symptom Rating Scale (GSRS). Responsiveness to change was assessed using F-statistics. The minimally changed group was those somewhat better or somewhat worse on the retrospective anchors and changing by one category on the modified GSRS (e.g., from slight to mild discomfort to moderate to moderately severe discomfort). RESULTS: Responsiveness to change was statistically significant for 6 of 8 PROMIS scales using the self-report GI anchor, 3 of 8 scales using the physician-reported anchor, and 5 of 5 scales using the corresponding GSRS scales as anchors. The MID estimates for scales for improvement and worsening were about 0.5-0.6 SD using the GSRS anchor and generally larger in magnitude than the change for the "about the same" group. CONCLUSIONS: The responsiveness and MID estimates provided here for the PROMIS GI Symptoms scales can aid in scale score interpretation in clinical trials and observational studies.

Development of the NIH Patient-Reported Outcomes Measurement Information System (PROMIS) gastrointestinal symptom scales.

OBJECTIVES: The National Institutes of Health (NIH) Patient-Reported Outcomes Measurement Information System (PROMIS(®)) is a standardized set of patient-reported outcomes (PROs) that cover physical, mental, and social health. The aim of this study was to develop the NIH PROMIS gastrointestinal (GI) symptom measures. METHODS: We first conducted a systematic literature review to develop a broad conceptual model of GI symptoms. We complemented the review with 12 focus groups including 102 GI patients. We developed PROMIS items based on the literature and input from the focus groups followed by cognitive debriefing in 28 patients. We administered the items to diverse GI patients (irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), systemic sclerosis (SSc), and other common GI disorders) and a census-based US general population (GP) control sample. We created scales based on confirmatory factor analyses and item response theory modeling, and evaluated the scales for reliability and validity. RESULTS: A total of 102 items were developed and administered to 865 patients with GI conditions and 1,177 GP participants. Factor analyses provided support for eight scales: gastroesophageal reflux (13 items), disrupted swallowing (7 items), diarrhea (5 items), bowel incontinence/soilage (4 items), nausea and vomiting (4 items), constipation (9 items), belly pain (6 items), and gas/bloat/flatulence (12 items). The scales correlated significantly with both generic and disease-targeted legacy instruments, and demonstrate evidence of reliability. CONCLUSIONS: Using the NIH PROMIS framework, we developed eight GI symptom scales that can now be used for clinical care and research across the full range of GI disorders.