Laboratory diagnostics in transient loss of consciousness. Serum lactate compared to serum creatine kinase as diagnostic indicator for generalized tonic-clonic seizures

Laboratory parameters can help in the differential diagnostics of acute episodes of transient loss of consciousness. Especially serum lactate and serum creatine kinase (CK) levels may provide valuable hints to distinguish generalized tonic-clonic seizures (GTCS) from syncope. Serum lactate levels at admission and CK levels 10-48 h after the episodes that led to admission were compared between patients with GTCS (n = 30) and those with syncope (n = 15). In addition, sensitivity and specificity of lactate and CK as diagnostic markers for syncope and GTCS were determined. The serum lactate and serum CK levels were significantly increased in patients with GTCS as compared to syncope patients (serum lactate: p < 0.001; CK: p < 0.005). The area under the curve (AUC) for serum lactate as an indicator for GTCS was 0.94 (95% confidence interval [CI] 0.88-1.0). For CK the receiver operating characteristics (ROC) analysis produced an AUC of only 0.77 (95% CI: 0.63-0.9). The determination of the lactate value as point-of-care diagnostics appears to be highly relevant in the rapid clarification of unclear episodes with transient loss of consciousness. The CK level at follow-up is also suitable for distinguishing GTCS from syncope but is inferior to the serum lactate value.