Investigating food-related behaviors in Smith-Magenis syndrome: tailoring a questionnaire for a rare disease

Abstract Purpose Accurate measurement is essential for tracking changes in clinical outcomes. Individuals with Smith-Magenis syndrome (SMS) exhibit challenging and unique food-related behaviors. We sought to determine the best tool to capture their unique food-related behaviors. Methods We conducted focus groups with caregivers of individuals with SMS to evaluate two commonly used questionnaires for food-related behaviors– the Food Related Problems Questionnaire (FRPQ) and the Hyperphagia Questionnaire for Clinical Trials (HQ-CT). Based on caregiver input and clinical expertise, we adapted these existing measures into a new tool: the SMS-FRPQ. We then validated this instrument for internal consistency and concurrent validity using online responses from 125 caregivers. Results Caregivers (n = 24) indicated neither the FRPQ or HQ-CT fully captured their child’s food-related behaviors; however, the newly developed SMS-FRPQ was deemed comprehensive by a new group of caregivers (n = 19). The SMS-FRPQ demonstrated strong internal consistency, with a Cronbach’s alpha of α = 0.87 [0.84–0.90]. Factor analysis indicated a three-factor model was a good fit (comparative fit index (CFI) = 0.9, Tucker-Lewis index (TLI) = 0.88). The three factors each showed good internal consistency: Desire for Food, α = 0.80 [0.74–0.85]; Takes Food, α = 0.87 [0.83–0.90]; Satiety Impairment, α = 0.83 [0.77–0.87]. The SMS-FRPQ showed higher internal reliability than the FRPQ. Concurrent validity was supported through alignment with similar items from the HQ-CT or Behavioral Problems Inventory (BPI-01). Conclusions The SMS-FRPQ has 14 items across 3 different factors and 5 additional clinically relevant items. This validated tool may be useful for tracking food-related behavior outcomes in clinical trials for this high-risk population.