Utility of laboratory testing for infants with seizures

Objectives: Study objectives were to 1) determine the frequency with which laboratory studies are obtained, 2) determine the proportion of results tha t are clinically significantly abnormal, and 3) define the clinical charact eristics of those with abnormal results, among infants with nonfebrile seiz ures (NFSz). Methods: A retrospective consecutive cohort study of infants less than or e qual to 12 months old presenting to the ED of a tertiary care, children's h ospital following a seizure. A 2-year review was performed. Serum chemistry results were classified as "normal," "outside of the normal range," or "cl inically significantly abnormal." Results: Sixty-seven of 134 (50%) with a NFSz were tested compared to 19/80 (24%) with a febrile seizure (FSz, P < 0.001). Nine (5 with hyponatremia a nd 4 with hypocalcemia) of the 67 (13%) tested NFSz infants had a clinicall y significant abnormality, as did 9 of 21 (43%) NFSz infants who seized in the ED compared to 0/46 (0%),Without ED seizure activity (P < 0.0001). Hypo thermia (T < 36.5 degrees C) and age less than I month were common characte ristics of infants with clinically significant abnormalities. Conclusions: This is one of the only studies to have assessed the utility o f laboratory testing for infants with seizures. Abnormal serum chemistries accounted for a greater proportion of seizures among this cohort compared t o that reported previously for older children. Laboratory testing is recomm ended for NFSz infants who 1) are actively seizing in the ED, 2) have a tem perature below 36.5 degrees C, or 3) are less than 1 month of age.