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Published on: July 31, 2016
Caregiver Meaningful Score Differences and Meaningful Score Regions for the Observer-Reported Communication Ability
Abigail Rader1, Li Lin1, Anjali Sadhwani2
1Center for Health Measurement, Department of Population Health Sciences, Duke University School of Medicine, Durham, NC, USA.
Objectives:
This study presents a novel method for estimating meaningful score differences (MSDs) and meaningful score regions (MSRs) for the Observer-Reported Communication Ability (ORCA) Measure for individuals with Angelman syndrome (AS).
Methods:
The AS Natural History Study collected longitudinal data on an individual's communication abilities on the ORCA Measure, Vineland Adaptive Behavior Scales-3, and the Bayley Scales of Infant and Toddler Development-4. In a separate Delphi-based study, caregivers provided MSDs and MSRs for the Vineland-3 and Bayley-4 scores. Leveraging the strong correlations between ORCA and these measures, mixed models with random intercepts were used to estimate ORCA MSDs and MSRs based on the previously derived Vineland-3/Bayley-4 MSDs and MSRs.
Results:
The ORCA Measure was completed by 192 caregivers, with 113 also completing the Bayley-4 and 159 completing the Vineland-3. ORCA T-score MSRs for low, intermediate, and high communication ability were estimated for expressive, receptive, and pragmatic communication domains using the Vineland-3 and Bayley-4 previously derived MSDs and MSRs. ORCA MSDs varied depending on the MSR and ranged from 0.38-4.55 (based on Vineland-3) and 1.79-4.62 (based on Bayley-4).
Conclusions:
We present a novel anchor-based methodological approach for deriving MSD and MSR thresholds for clinical outcome assessments. Although these MSD and MSR estimates for the ORCA measure are preliminary, our methods offer a strategy for establishing meaningful change thresholds in rare disease populations in which traditional longitudinal methods may be challenging to implement.
