Accuracy of an online tool to assess appropriateness for an epilepsy surgery evaluation-A population-based Swedish study

Objective: The Canadian Appropriateness of Epilepsy Surgery (CASES) tool was developed to help physicians identify patients who should be referred for an epilepsy surgery evaluation. The aim of this study was to determine the accuracy of this tool using a population-based cohort registry (the Swedish National Epilepsy Surgery Register) of patients who underwent epilepsy surgery between 1990 and 2012. Methods: Overall, 1044 patients met eligibility criteria for the study and were deemed to be surgical candidates by epilepsy experts. Demographic and epilepsy related characteristics were examined and summarized using descriptive statistics. A CASES appropriateness score was calculated for each of these patients. Chi squared analyses or fisher's exact tests were used to determine if there were any relationships between demographic and epilepsy related characteristics not captured in the tool and appropriateness scores. Results: The mean appropriateness score was 8.6 and 985 (Sensitivity: 94.35%; 95% CI, 92.77%-95.60%) patients were appropriate, 46 (4.41%; 95% CI, 3.31%-5.84%) were uncertain, and 13 (1.25%; 95% CI, 0.72%-2.13%) were inappropriate for an epilepsy surgery evaluation. The mean necessity score, which was only calculated for the 985 appropriate patients, was 8.7. All 13 inappropriate patients had tried less than two antiepileptic drugs (AEDs). In addition, age at onset of epilepsy and age at epilepsy surgery were both significantly associated with appropriateness score. Conclusions: These results demonstrate that the CASES tool is highly sensitive as it designated 94.3% of epilepsy surgery patients as appropriate for an epilepsy surgery evaluation. All of those classified as inappropriate were not drug resistant, as they had not yet tried two AEDs.