Hawe E, Stull DE, McBride D, Balp M. Estimating utility data for patient symptom severity in chronic spontaneous urticaria. Poster presented at the 17th Annual European Congress of the International Society for Pharmacoeconomics and Outcomes Research; November 2014. Amsterdam, the Netherlands.

OBJECTIVES: To obtain utility estimates suitable for use in economic models for chronic spontaneous (idiopathic) urticaria (CSU).

METHODS: Patient-level data from three randomised clinical trials: ASTERIA I, ASTERIA II, and GLACIAL were analysed. Health states were derived from Urticaria Activity Score (UAS7), a patient-completed diary of signs and symptoms which calculates an average daily score over 7 days. Higher score means more severe symptoms. UAS7 scores for the health states were: Urticaria-free: 0; Well-controlled urticaria: 1-6; Mild urticaria: 7-15; Moderate urticaria: 16-27; Severe urticaria: 28-42. Mean EQ-5D utilities were calculated for each health state. Individual trial analyses showed inconsistent utilities across the UAS7 health states due to small subsample sizes. A mixed model was used to predict EQ-5D according to UAS7 health states in a pooled dataset containing all treatment arms and time-points from the three trials. The predictor variable was UAS7 health state and the dependent variable was EQ-5D utility. Fixed/random effects for trial and patient were included and the following covariates: UAS7 health state at baseline (Moderate or Severe), presence of angioedema at baseline and during follow-up, duration of CSU, number of previous CSU medications, and gender of the patient. A parsimonious model was selected using the approach of backwards elimination; UAS7 health state was forced into the model. The validity of pooling trials was considered through visual comparisons and interaction terms.

RESULTS: There was a consistent improvement in EQ-5D utilities as severity of urticaria improved. Mean utilities at Week 12 ranged from 0.712 in patients with severe urticaria to 0.897 in patients who were urticaria-free. Sensitivity analysis confirmed the robustness of results.

CONCLUSIONS: The results suggest that EQ-5D utility score increased with decreasing severity of urticaria. EQ-5D utility scores allow the comparison of HRQoL across diseases by calculating QALYs in economic models.

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