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 2h 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 2.45mmol/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.