Changes in quality of life after epilepsy surgery: the role of reprioritization response shift

Objectives: Health-related quality of life (HRQOL) is an important indicator of well-being in patients with epilepsy. When assessing changes in HRQOL over time, some of the changes observed may be due to the patients' change in the internal standards, value, or meaning that they attribute to the HRQOL domain being measured, rather than actual change, a phenomenon known as response shift. Response shifts are increasingly recognized as an important explanation for the seemingly paradoxical or counterintuitive HRQOL results often observed in chronic conditions. We investigated the presence of changing values (reprioritization response shift) in data from a surgical randomized controlled trial of patients with temporal lobe epilepsy (TLE).

Methods: Eighty patients with TLE, who were randomized to surgical and medical treatment, provided data on the epilepsy-specific 31-item Quality of life in Epilepsy (QOLIE-31) questionnaire at baseline and 1 year after randomization. Reprioritization response shift among the seven QOLIE-31 domains was assessed using changes in the relative importance weights derived from logistic regression and discriminant analysis.

Results: The relative importance analysis showed a statistically significant increase over time in the importance of social function, but a significant decrease in the relative importance of seizure worry. There were no significant changes in the relative importance of the remaining five domains in distinguishing between surgical and medical group over time.

Significance: Patients that receive surgical treatment are more likely to experience a decrease in the valuation of seizure worry and an increase in the value of social function as compared to patients who are medically treated. Changes in expectation about seizure freedom and social function may confound the assessment of longitudinal change on these outcomes, and highlight the importance of assessing response shift and the limitations of assessing HRQOL at a single point in time or without a control group. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.