An anion gap above 10, measured in the first 2 hours after a seizure, may help clinicians in the emergency department distinguish between psychogenic nonepileptic seizures (PNES) and generalized convulsive epileptic seizures (ES), according to an analysis of more than 1300 patients at a tertiary care center. Details of the analysis include the following:
- Investigators looked at anion gap, bicarbonate, and Denver Seizure Scores and found 27 patients with PNES and 27 with ES, using clinical signs and symptoms in conjunction with EEGs.
- Multivariate logistic regression helped detect a link between an anion gap above 10 and seizure type but also found that sensitivity and negative predictive value dropped off dramatically when samples were drawn more than 2 hours after the event.
- Anion gap values above 10 yielded a sensitivity of 81.8% and specificity of 100% when measured within 2 hours of the seizure.
Li Y, Matzka L, Maranda L, Weber D. Anion gap can differentiate between psychogenic and epileptic seizures in the emergency setting. Epilepsia. 2017;58(9):e132-e135.