Content validity of the Familial Chylomicronemia Syndrome Symptoms and Impacts Scale (FCS-SIS) for severe hypertriglyceridemia (sHTG)

Objective: Severe hypertriglyceridemia (sHTG) and familial chylomicronemia syndrome (FCS) are metabolic conditions associated with an increased risk of adverse health outcomes. The FCS Symptoms and Impacts Scale (FCS-SIS) was developed to assess the symptoms and impacts of FCS. This study assessed the content validity of the 4 FCS-SIS symptom items in adults with sHTG. Methods: Two iterative rounds of qualitative interviews were conducted with adults (aged ≥ 18 years) who had clinician-confirmed sHTG (triglycerides ≥ 500 mg/dL) and recently experienced ≥ 2 symptoms of sHTG. Participants described their initial experiences and symptoms of sHTG during concept elicitation. Cognitive debriefing of the 4 FCS-SIS symptom items assessed relevance, interpretability, answerability, and meaningful change. Results: Among 20 participants, the most frequently reported, most bothersome, and most important-to-treat sHTG symptoms were difficulty thinking (n = 20), physical fatigue (n = 20), diarrhea (n = 19), and abdominal pain (n = 18), which the 4 FCS-SIS symptom items assess. Participants reported these items to be easy to understand (n = 20) and, for most items, reported that a 1- to 2-point improvement would be meaningful. Conclusion: FCS-SIS symptom items are content-valid items for the assessment of sHTG symptoms in adults with sHTG.