Validation of the Bulgarian version of the quality of life in epilepsy inventory (QOLIE-89).

Introduction: The quality of life in epilepsy inventory (QOLIE-89) is the most comprehensive and widely used instrument for assessment of the quality of life of patients with epilepsy.

Aim: To prove that the Bulgarian version of QOLIE-89 shows good reliability and validity.

Patients And Methods: The study included 35 patients with refractory epilepsy: 20 women (57.14%) and 15 men (42.86%) at the mean age of 43.11 +/- 2.38 years and mean duration of epilepsy 22.46 +/- 2.05 years. All respondents completed QOLIE-89 twice at an interval of one to three weeks; they also completed QOLIE-31 once.

Results: Cronbach's alpha was between 0.90 and 0.92 for all subscales, the mean assessment score was 0.91. These results, the high Spearman-Brown coefficient (0.90) and the low mean inter-item correlation (0.33) suggest that the Bulgarian version of QOLIE-98 shows excellent internal consistency and high reliability. This is supported by the high coefficient of correlation (0.83-0.98) between the subscales scores and the overall assessment of the quality of life in the two completions of the questionnaire. The questionnaire proved to be valid based on the strong correlation we found between the overall assessment score (0.91) of QOLIE-31 and QOLIE-89 and the subscales of seizure worry, overall quality of life, energy/fatigue and overall scores--all in the range of 0.95-1.00. The correlations of coefficients for the other subscales were between 0.69-0.86.

Conclusions: The psychometric properties of the Bulgarian version of QOLIE-98 are good; they are similar to those of the original American version and the validated Norwegian and Chinese versions. It shows high reliability and validity and can be used to assess the quality of life of elderly people with epilepsy.