Psychometric evaluation of the Serbian version of the Quality of Life in Epilepsy Inventory-31 (QOLIE-31)

Abstract Purpose To evaluate the psychometric properties of the Serbian-language version of the Quality of Life in Epilepsy Inventory-31 (QOLIE-31). Methods After undergoing a translation and cultural adaptation of its items in order to create a Serbian-language version of QOLIE-31, we assessed its psychometric properties—reliability, construct validity and criterion validity. The sample consisted of 203 adults with epilepsy. Reliability was tested both by assessing the internal consistency and by the test–retest method. Construct validity was assessed by factor analysis, multitrait-scaling analysis and method of known-groups validation. This was achieved by assessing the relationship between scales and external measures (socio-demographic characteristics, seizure severity and etiology of epilepsy). Criterion validity was assessed by correlation analysis between QOLIE-31 and Short form 36 health survey (SF-36) and Neurotoxicity scale-II. Results The domains showed high internal consistency (Cronbach's α 0.94). Test–retest reliability for Overall test score was 0.83 (Pearson's coefficient) indicating temporal stability. Seizure severity and etiology of epilepsy significantly influenced all QOLIE-31 domains except the Medication effect domain, with lowest scores in high seizure severity and symptomatic etiology groups. Employment status significantly influenced Overall quality of life, Emotional well-being, Social function and Overall score. Educational level was related to the Emotional well-being domain, with highest scores for students. The QOLIE-31 was highly positively correlated with SF-36 (rho=0.898) and strongly negatively correlated with Neurotoxicity scale-II (rho=−0.783). Conclusion Serbian adaptation of the QOLIE-31 questionnaire is reliable and valid for assessing the quality of life in patients with epilepsy.