Lactate as a diagnostic marker in transient loss of consciousness

Purpose: The diagnostic classification of disorders of consciousness is often challenging, particularly the distinction between epileptic and non-epileptic seizures. The aim of the study was to examine serum lactate as a diagnostic marker of transient loss of consciousness. Method: Serum lactate levels in blood samples drawn within 2 h of the event were compared retrospectively between patients with generalized tonic-clonic seizures (n = 195) and patients with other seizures (syncopes [n = 52], psychogenic non-epileptic seizures [n = 17], and complex focal seizures [n = 37]), respectively. Results: Serum lactate in patients with generalized tonic-clonic seizures was significantly (p < 0.001, Mann-Whitney-U test) increased in comparison to other forms of seizure incidences. The area under the ROC-curve was 0.94 (95% CI 0.91-0.96). For a cut-off concentration of 2.45 mmol/l, the sensitivity was 0.88 and the specificity 0.87. Conclusions: Serum lactate levels in the acute diagnosis were an excellent biomarker for the discrimination of generalized seizures from psychogenic non-epileptic and syncopal events, corroborating its importance for the standard work-up of acute disturbances of consciousness. (C) 2016 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.