Utility of laboratory testing for infants with seizures

Study objectives were to 1) determine the frequency with which laboratory studies are obtained, 2) determine the proportion of results that are clinically significantly abnormal, and 3) define the clinical characteristics of those with abnormal results, among infants with nonfebrile seizures (NFSz).

A retrospective consecutive cohort study of infants < or = 12 months old presenting to the ED of a tertiary care, children's hospital following a seizure. A 2-year review was performed. Serum chemistry results were classified as "normal," "outside of the normal range," or "clinically significantly abnormal."

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 and 4 with hypocalcemia) of the 67 (13%) tested NFSz infants had a clinically 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). Hypothermia (T < 36.5 degrees C) and age less than 1 month were common characteristics of infants with clinically significant abnormalities.

This is one of the only studies to have assessed the utility of laboratory testing for infants with seizures. Abnormal serum chemistries accounted for a greater proportion of seizures among this cohort compared to that reported previously for older children. Laboratory testing is recommended for NFSz infants who 1) are actively seizing in the ED, 2) have a temperature below 36.5 degrees C, or 3) are less than 1 month of age.