Disease-targeted versus generic measurement of health-related quality of life in epilepsy

Purpose: To assess (1) whether the generic Short Form (SF)-36, an integrated component of the epilepsy-targeted Quality of Life in Epilepsy Inventory-89 (QOLIE-89), is able to detect differences in the health-related quality of life (HRQOL) between young adults with epilepsy and healthy sibling controls and (2) whether the generic components are as sensitive to within-disease symptom severity as the epilepsy-targeted components of the QOLIE-89 in young adults with epilepsy. Methods: A cohort of young adults with epilepsy (N = 108, age 21.6 years SD = 3.8), followed since diagnosis in a prospective community-based study of childhood-onset epilepsy, completed the QOLIE-89, an epilepsy-targeted HRQOL instrument that includes within it a generic core measure (SF-36). Sibling controls (N = 82, age = 20.7 years, SD = 2.1) completed the generic core, SF-36. Results: Age- and gender-adjusted QOLIE-89 epilepsy-targeted and cognitive-distress composite scores and the overall score were strongly associated with seizure-free duration: seizure-free ≥5 years (higher HRQOL), n = 57; seizure-free 1–5 years, n = 22; or seizure-free <1 year, n = 29 (lower HRQOL) (p < 0.001). However, on QOLIE-89 physical health and mental health composite scores, there were no differences across these seizure-free duration groups. For cases compared with sibling controls, there were no differences on SF-36 physical and mental health composite scores or the global composite score, using either classical test or item-response theory scoring procedures. Conclusions: While the epilepsy-targeted components of the QOLIE-89 are sensitive to seizure-related factors in young adults with epilepsy, the SF-36 generic core measures are not, thereby limiting HRQOL comparisons between young adults with epilepsy and sibling controls.