Differentiation between psychogenic nonepileptic seizures (PNES) and generalized convulsive epileptic seizures (ES) is important for appropriate triaging in the emergency department (ED). This can be difficult in the ED, as the event is often not witnessed by a medical professional. In the current study, we investigated whether anion gap (AG), bicarbonate, and the Denver Seizure Score (DSS) could differentiate between PNES and ES. Of a total of 1,354 subjects reviewed from a tertiary care medical center, 27 PNES and 27 ES patients were identified based on clinical description and subsequent electroencephalogram. Multivariate logistic regression analysis and receiver operating characteristic curves were used to determine whether there was an association between seizure type and AG, bicarbonate, or DSS (24-bicarbonate + 2 × [AG-12]) when samples were drawn within 24 h of the concerning event. The result showed that sensitivity and negative predictive value dropped markedly for all measures if samples were drawn >2 h after the event; the sensitivity was similar for AG and DSS and higher than for bicarbonate. We propose that AG > 10 (sensitivity of 81.8%, specificity of 100%) in the first 2 h after the event could be used as a potential tool in the ED to help differentiate between PNES and ES.
Summary
Epileptic seizures (ES) and psychogenic nonepileptic seizures (PNES) can be difficult to differentiate from each other in the emergency department (ED) setting. We have previously shown that the anion gap (AG) can help differentiate between ES and PNES in the ED. In this study, we explored whether additionally considering leukocytosis can help better differentiate between ES and PNES. We screened a total of 1354 subjects seen in the ED of a tertiary care medical center; 27 PNES and 27 ES patients were identified based on clinical description and subsequent electroencephalography (EEG). Multivariable logistic regression analysis was used to model the association between ES, leukocytosis, and AG. Our results indicated that within 9 hours after the index event, serum AG (adjusted odds ratio [aOR] 2.07) and white blood cell (WBC) count (aOR 1.61) were both independently associated with ES. We derived an equation to help differentiate between ES and PNES: 1.5*AG+WBC. A score >24.8 indicated a >90% likelihood of ES. A score <15.5 indicated a <10% likelihood of ES (ie, the alternate diagnosis of PNES should be considered). This study for the first time provides evidence to help differentiate PNES and ES utilizing acidosis and leukocytosis.
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