ADVANCES IN METHODS FOR ASSESSING THE IMPACT OF EPILEPSY AND ANTIEPILEPTIC DRUG-THERAPY ON PATIENTS HEALTH-RELATED QUALITY-OF-LIFE

We studied 31 previously validated and newly developed generic and epi lepsy-specific scales to evaluate their usefulness for assessing the i mpact of epilepsy and anti-epileptic drug (AED) therapy on health-rela ted quality of life (HRQOL). Included were the MOS SF-36 Health Survey , additional measures of mental health, cognition, epilepsy-specific p erception of control, behavioural problems, distress, worries and expe riences, the Liverpool Epilepsy Impact and Seizure Severity scales, an d a patient-completed symptom checklist. Questionnaires were completed twice by 136 patients on AED therapy in a multicentre study in the UK . Validity was assessed in relation to disease severity, defined as ti me since last seizure, and to patient-reported symptoms. Statistical a nalyses to estimate the contribution of HRQOL information of each scal e relative to that of others were conducted. The 171-item questionnair e could be completed by out-patients with epilepsy with good data qual ity. With few exceptions, generic and epilepsy-specific measures satis fied psychometric tests of hypothesized item groupings and scale score reliability (internal consistency and test-retest reliability) and di fferentiated well between groups of patients differing in time since l ast seizure and in symptom impact, regardless of time since last seizu re. However, scales differed widely in their validity in discriminatin g between groups of patients known to differ clinically. The SF-36 Rol e Physical scale best discriminated among groups differing in disease severity. The epilepsy-specific Mastery, Impact, Experience, Worry, Di stress, and Agitation scales were among the 10 best measures in discri minating among groups differing in disease severity. Generic measures, especially measures of social and role functioning and mental health, were best at differentiating groups of patients differing in symptom impact. Recommendations are offered for concepts and specific scales m ost likely to be useful in future studies of the HRQOL burden of epile psy and the HRQOL benefits of AED therapy.