Development and psychometric evaluation of the Diabetic Gastroparesis Symptom Severity Diary
Received 15 August 2018
Accepted for publication 12 December 2018
Published 22 February 2019 Volume 2019:12 Pages 93—103
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 3
Editor who approved publication: Dr Anastasios Koulaouzidis
Sheri Fehnel,1 Fred T Fiedorek,2 Lauren Nelson,1 Dana DiBenedetti,1 Sharon Spence,2 Robyn T Carson3
1Patient-Centered Outcomes Assessment, RTI Health Solutions, Research Triangle Park, NC, USA; 2Motus Therapeutics, Inc., Boston, MA, USA; 3Patient-Centered Outcomes Research, Global Evidence and Value Development, Allergan plc, Madison, NJ, USA
Background: Diabetic gastroparesis (DG) is defined as delayed gastric emptying with associated gastrointestinal symptoms, without mechanical obstruction. Patient-reported symptoms are critical for diagnosis and evaluation of treatment benefit in DG. The Diabetic Gastroparesis Symptom Severity Diary (DGSSD), a new patient-reported outcome measure, was developed for use in clinical trials to support product approval and labeling claims for DG treatments.
Materials and methods: Initial DGSSD development was based on a review of the existing instruments and qualitative research (focus groups and cognitive debriefing interviews) in 41 patients with DG. Psychometric evaluations (individual items and composite scores) were conducted using data from Phase IIa and IIb relamorelin clinical trials.
Results: Qualitative research in patients with DG resulted in a six-item DGSSD, included in the Phase IIa trial, addressing symptom severity for nausea, vomiting, abdominal pain, early satiety, and bloating, as well as vomiting frequency. An item addressing severity of postprandial fullness (PPF) was subsequently added based on regulatory advice and included in the Phase IIb trial. Measurement properties were generally strong for weekly averages of daily item and composite scores. Item-level intraclass correlation coefficients ranged from 0.79 to 0.97 and correlations with other measures matched hypothesized patterns; the discriminating ability and responsiveness of the DGSSD were also supported. Multiple methods supported the computation of a composite score based on items addressing nausea, abdominal pain, bloating, and PPF severity.
Conclusion: Qualitative and quantitative evidence support use of the DGSSD as a reliable and valid measure from which to derive endpoints to evaluate treatment benefit in future DG interventional trials.
Keywords: diabetes, relamorelin, patient-reported outcome, instrument
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