Seizures associated with fever: clinical data as predictors for normal biochemical blood levels

Abstract

We developed a predictive model to assess the probability of normal biochemical blood test results in children presenting with a seizure associated with fever. The models were based on various combinations of patient characteristics of the history and physical examination of 203 children. The characteristics included gender, age in years, previous history of febrile seizures, family history of febrile seizures, fever previous to the seizure, vomiting and diarrhoea previous to the seizure. Further, clinical characteristics of the seizure were considered: focal seizure signs, multiple seizure, seizure duration and rectal temperature at seizure. The outcome was defined as normal test results of serum levels of sodium (n=115, 68%), calcium (n=149, 89%) and glucose (n = 173, 100%), according to the hospital reference values. The prevalence of abnormal test results was rather low and the abnormalities were outside the morbidity range. We used logistic regression to relate the outcome to the several clinical characteristics. The discriminative ability of the models was 0.63 (area under the receiver operating characteristic curve of the model predicting normal sodium), 0.66 (normal calcium) and 0.66 (both normal). The score chart we constructed is an additional tool to a carefully performed patient history and physical examination and it may help to decide if a biochemical test is indicated for the individual patient.

Conclusion In children with seizures associated with fever, abnormal biochemical blood test results are rare and outside the morbidity range. The biochemical tests are generally not required. In children with a low probability of a normal result as calculated by the score chart, the test may be indicated.