181 PREDICTION OF SEIZURE RECURRENCE AFTER A FEBRILE SEIZURE

Abstract

Of all children with febrile seizures (FS) 15 to 80% are reported to have recurrent FS. Children at increased risk of frequent recurrences might be candidates for some form of prophylactic treatment. Accurate assessment of the individual child's recurrence risk is therefore essential. To determine the risk of subsequent seizures after a 1st, 2nd or 3rd episode of FS we used the findings of our large collaborative cohort study (J Pediatr 1994, April issue). Data on 2496 children with a total number of 3459 episodes at risk for a subsequent FS until the age of 5 years were examined. The overall recurrence rate after a 1st, a 2nd or 3rd FS was 32%, 47% and 49% respectively. A child's attained age was the most important determinant of seizure recurrence. Other significant factors were a first degree family history of febrile or unprovoked seizures and a temperature < 40.0°C at the first FS; the number and recency of previous experienced FS provided additional information. These risk factors were examined multivariate and combined into a prognostic index for each single child. Estimated recurrence risk and observed number of recurrences were compared in various risk strata, the predictive validity of the model was assessed using the individual data on 347 children from a recently published follow up study (N Engl J Med 1992:327:1122-7). For a child with a first FS recurrence at 18 months and no risk factors, the estimated probability of further seizures up to the age of 5 years is 47%, if a second recurrence occurs at 30 months, this risk becomes 26%. Patients allocated by the prognostic index into the highest of five risk groups had an observed recurrence risk of 89% at 5 years, with a predicted value of 85%. Corresponding results for low risk were 9% observed) and 7% (predicted), for medium risk 31% and 31%, respectively. We conclude that this prognostic index identifies children at high and low risk for requent recurrences and can be a useful tool for clinical practice.