Utility of laboratory studies in the emergency department patient with a new-onset seizure

Extensive laboratory testing is often performed in the emergency department evaluation of the new-onset seizure patient. To determine the utility of such testing, a prospective study of patients with a new-onset seizure presenting to the ED of an inner-city, university-affiliated teaching hospital was done. One hundred thirty-six patients were entered into the study between October 1984 and January 1988. All patients had uniform data collection performed. Pertinent historical information and physical examination findings were recorded on a standardized form before laboratory abnormality was a sole or contributory cause of the seizure disorder. These included four patients with hypoglycemia, four with hyperglycemia, two with hypocalcemia, and one with hypomagnesemia. Only two cases (hypoglycemia) were not suspected on the basis of findings on the history or physical examination. In ED patients, the incidence of a new-onset seizure due to a correctable metabolic disturbance is low. We conclude that, with the exception of the serum glucose, the extensive ED laboratory workup often done for the evaluation of a new-onset seizure is unnecessary. Further test ordering should be directed by the medical history and physical examination.