COMPARISON OF DAILY VS WEEKLY ADMINISTRATION FORMATS OF THE GLYCOGEN STORAGE DISEASE FUNCTIONAL ASSESSMENT DIARY (GSD FAD)
Author(s)
Adrian Jewett, MA1, Brandon Foster, PhD1, Deepali Mitragotri, PhD2, Jessica Butler, BA2, Shayna Egan, MPH2, Ashley Willis, BA1, Diane M. Turner-Bowker, PhD2;
1Lumanity, Boston, MA, USA, 2Ultragenyx Pharmaceutical Inc., Novato, CA, USA
1Lumanity, Boston, MA, USA, 2Ultragenyx Pharmaceutical Inc., Novato, CA, USA
OBJECTIVES: The GSD FAD is a 31-item, disease-specific patient-reported outcome (PRO) that measures the signs/symptoms and impacts associated with Glycogen Storage Disease Type Ia (GSDIa). It was developed as a daily eDiary in the DTX401-CL301 Phase 3, randomized, double-blind, placebo-controlled study investigating the efficacy and safety of DTX401 in individuals ≥8 years living with GSDIa (NCT05139316). This analysis compared score equivalency between two administration formats of the GSD FAD: (1) a daily version that instructs subjects to report signs/symptoms and impacts “today”, with scores calculated as daily total scores, averaged over a 7-day period; and (2) a less burdensome once-weekly version that instructs subjects to report signs/symptoms and impacts experienced over the past 7 days, with scores calculated as total scores.
METHODS: Psychometric analyses were performed using WK48 and WK96 data from the Intent-to-Treat population, defined as all randomized subjects who received investigational DTX401 or Placebo. All analyses were conducted using R version 4.4.0 or higher.
RESULTS: Descriptive summaries of the scores at WK48 and WK96 showed slight differences, but overall, results were comparable between the two formats. The scores also exhibited acceptable internal consistency reliability (α ≥ 0.70) with similar estimates across formats. Most scores demonstrated acceptable intra-rater reliability (ICC[C,1] ≥ 0.70) across formats, though a few fell below the threshold. However, the sample size for these analyses was limited, and estimates just under the performance threshold would likely result in higher estimates in a larger sample. All scores showed adequate convergent validity (rs ≥ 0.30) with moderate to very strong correlations, indicating that corresponding scores from each form measure concepts similarly.
CONCLUSIONS: Results suggest that Daily and Weekly formats can be considered alternate forms and provide initial evidence to support the use of the Weekly GSD FAD version in research settings where the administration of a daily eDiary is not feasible.
METHODS: Psychometric analyses were performed using WK48 and WK96 data from the Intent-to-Treat population, defined as all randomized subjects who received investigational DTX401 or Placebo. All analyses were conducted using R version 4.4.0 or higher.
RESULTS: Descriptive summaries of the scores at WK48 and WK96 showed slight differences, but overall, results were comparable between the two formats. The scores also exhibited acceptable internal consistency reliability (α ≥ 0.70) with similar estimates across formats. Most scores demonstrated acceptable intra-rater reliability (ICC[C,1] ≥ 0.70) across formats, though a few fell below the threshold. However, the sample size for these analyses was limited, and estimates just under the performance threshold would likely result in higher estimates in a larger sample. All scores showed adequate convergent validity (rs ≥ 0.30) with moderate to very strong correlations, indicating that corresponding scores from each form measure concepts similarly.
CONCLUSIONS: Results suggest that Daily and Weekly formats can be considered alternate forms and provide initial evidence to support the use of the Weekly GSD FAD version in research settings where the administration of a daily eDiary is not feasible.
Conference/Value in Health Info
2026-05, ISPOR 2026, Philadelphia, PA, USA
Value in Health, Volume 29, Issue S6
Code
MSR224
Topic
Methodological & Statistical Research
Topic Subcategory
PRO & Related Methods
Disease
SDC: Diabetes/Endocrine/Metabolic Disorders (including obesity), SDC: Rare & Orphan Diseases