The subjective handicap of epilepsy. A new approach to measuring treatment outcome.

It is now widely acknowledged that the impact of epilepsy on the individual extends beyond the occurrence of seizures, and that there is a need for outcome measures sensitive to these consequences. Until now these instruments have largely been developed within a 'quality of life' framework. The technical and conceptual difficulties that arise with measuring quality of life have led us to develop a more focused measurement model, the 'Subjective Handicap of Epilepsy' (SHE) scale, based on the World Health Organization's concept of handicap. The scale contains 32 items in six subscales: 'Work and activities' (eight items), 'Social and personal' (four items), 'Self-perception' (five items), 'Physical' (four items), 'Life-satisfaction' (four items) and a 'Change' scale (seven items); and it takes on average < 10 min to complete. The scale's test-retest reliability was found to be satisfactory (intra-class correlation coefficient was 0.8-0.9 in 110 subjects). The test-retest interval (24 h to 8 weeks) had no influence on the reliability. The reliability was also not affected by minor recent fluctuations in seizure frequency. The internal consistency of the scales was 0.8-0.9 (Cronbach's alpha). The construct validity of the scale was examined in a sample of 287 clinic attendees at a university neurology clinic in the UK. The scales were highly sensitive to the handicapping effects of increasing seizure frequency, employment status, the impact of epilepsy on career choice and the subject's own opinion as to the major determinant of their quality of life. The scales were also sensitive, retrospectively, to the benefits of successful epilepsy surgery in a cohort of 105 patients. Scales focusing specifically on handicap were more sensitive to group differences in seizure frequency in the clinic population, and to outcome after epilepsy surgery, than the 'Life-satisfaction' scale and the Epilepsy Surgery Inventory 55 (ESI-55) scales. This supports the contention that measuring 'subjective handicap' may be a more sensitive, and more useful, approach to assessing the impact of interventions on the long-term consequences of epilepsy than current methods.