Aim: The differentiation between epileptic and non-epileptic episodes can be challenging. Our aim was to compare lactate, anion gap (AG), bicarbonate and the Denver Seizure Score (DSS) as point-of-care test (POCT) markers for episodes of transient alterations of consciousness.
Methods: The blood serum parameters were drawn at arrival in the emergency department (ED) within 2 h of the episode. After calculating AG and DSS values, the four parameters were compared retrospectively between patients with generalized tonic-clonic seizures (GTCS) (n = 165) and patients with other disorders of consciousness [syncopes (n = 43), and psychogenic non-epileptic seizures (n = 15)]. Additionally, we compared all values among men and women.
Results: In GTCS patients, all four parameters differed significantly compared to non-epileptic episode patients (p < 0.001). Serum lactate showed significant additional benefit over the remaining values, with an AUC of 0.947 (95% CI 0.92-0.975) and a high sensitivity and specificity for an optimal cut-off value of 2.45 mmol/l. For DSS, the AUC was 0.857 (95% CI 0.808-0.906; cut-off: 0.35), and for AG 0.836 (95% CI 0.783-0.889; cut-off: 12.45 mmol/l). In the case of serum bicarbonate, the AUC was 0.831 (95% CI 0.775-0.886; cut-off: 22.75 mmol/l). In the sex-dependent comparison, the results were similar. Men showed more significant differences in the compared values than women.
Conclusions: Serum lactate is best suited as POCT marker in the differential diagnosis of epileptic and non-epileptic episodes and is superior to AG, DSS and bicarbonate. The differences among sexes may pose a challenge in their implementation and interpretation.
Keywords: Anion gap; Bicarbonate; Denver seizure score; Diagnostic marker; Lactate; Seizure.