The role of postictal laboratory blood analyses in the diagnosis and prognosis of seizures.

BACKGROUND: Epileptic seizures (ES) lead to alterations in the blood laboratory values and reflect changes in different organ systems. Here, we review the diagnostic and prognostic value of various blood laboratory values within the context of epilepsy.

METHODS: Narrative review and literature search on PubMed using the term, "seizure" and various laboratory values.

RESULTS: Laboratory markers can help clinicians determine whether an unwitnessed event was more likely to be epileptic or non-epileptic. Prolactin testing helps differentiate ES from psychogenic non-epileptic seizures (PNES) in adults and adolescents, and is associated with high specificity and moderate sensitivity. Elevations in the creatine kinase (CK) levels are common after generalized tonic-clonic seizures (GTCS) and display high specificity and moderate sensitivity. Metabolic markers such as ammonia and lactate may have diagnostic potential for postictal blood tests. Analyzing blood postictally is important for identifying the cause of the symptomatic seizures due to endocrine, metabolic, toxic or infectious etiologies. Finally, laboratory analyses are used for identifying patients who are at risk for developing rare, threatening complications such as rhabdomyolysis, acute renal failure (ARF) or cardiomyopathy.

CONCLUSIONS: Presently, no postictal laboratory values can definitively prove or rule out the diagnosis of an epileptic seizure. For seizures with unknown causes, simple blood tests can be a valuable aid for quickly defining the etiology, particularly with certain metabolic and toxic encephalopathies. For this reason, CK, electrolytes, creatinine, liver and renal function tests should be measured on at least one occasion. Further research is needed in order to identify new biomarkers that improve the diagnosis and prognosis of seizures and seizure-related complications.