Psychometric Properties of the German Translation of the QOLIE-31

Abstract

The purpose of this work was to assess the psychometric properties of the German Translation of the Quality of Life in Epilepsy Inventory, QOLIE-31. Internal consistency, construct and criterion validity, and responsiveness were tested in 509 patients with epilepsy who were administered the questionnaires at application or at admittance to the epilepsy center Bethel. Construct validity was tested in patients with different seizure frequencies and different degrees of tolerability of antiepileptic drug (AED) therapy (adverse effects). The scales Epilepsy-Related Fears und Restrictions in Daily Life due to Epilepsy were used as criterion measures. Test-retest reliability (long-term stability) and responsiveness of the questionnaire were analyzed in subgroups of patients who responded to the questionnaires a second time (n = 256). Cronbach's alpha of the QOLIE-31 was 0.94 and varied between 0.76 and 0.90 for the seven subscales. The correlations of the QOLIE with Epilepsy-Related Fears and Restrictions in Daily Life revealed high correlations between Epilepsy-Related Fears and the QOLIE subscale Seizure Worry (r = 0.81, P < 0.01) and the total score (r = 0.62, P < 0.01) and between Restrictions in Daily Life and the QOLIE subscale Social Functioning (r = 0.71) and the total score (r = 0.70, P < 0.01). Seizure frequency had a significant effect especially on the QOLIE subscales Social Functioning, Seizure Worry, and Overall QOL, whereas tolerability of AED therapy affected especially the subscales Medication Effects, Overall QOL, and Energy-Fatigue. The test-retest reliability (intraclass correlation coefficient) was 0.79 for the overall score and varied between 0.59 and 0.78 for the seven subscales. The German Translation of QOLIE-31 is a reliable and valid questionnaire with which to assess QOL in patients with epilepsy and is conceptually similar to the English version. It is a sensitive questionnaire with respect to seizure frequency and tolerability of antiepileptic drug treatment.