Encephalitis laboratory tests


 * Associate Editors-In-Chief: Priyamvada Singh, MBBS [mailto:psingh@perfuse.org]

Overview
Encephalitis is an acute inflammation of the brain, commonly caused by a viral infection. Diagnosis is often made with detection of antibodies against specific viral agent (such as herpes simplex virus) or by polymerase chain reaction that amplifies the RNA or DNA of the virus responsible. Other lab tests that might be useful are complete blood count with differential, coagulation profile, serum electrolyte, urine electrolyte, serum glucose, blood urea nitrogen and serum creatinine levels (to rule out confusion due to dehydration), liver function test (to rule out hepatic involvement), lumbar puncture and CSF examination.

Lab tests

 * Complete blood count with differential
 * Coagulation profile
 * Serum electrolyte {helps to rule out syndrome of inappropriate secretion of antidiuretic hormone (SIADH)}
 * Urine electrolyte {helps to rule out syndrome of inappropriate secretion of antidiuretic hormone (SIADH)}
 * Serum glucose (helps to rule out confusion due to hypoglycemia, diabetic ketoacidosis and comparing serum glucose with CSF glucose)
 * Blood urea nitrogen and serum creatinine levels (to rule out confusion due to dehydration)
 * Liver function test (to rule out hepatic involvement
 * Lumbar puncture and CSF examination. Examination of the cerebrospinal fluid obtained by a lumbar puncture procedure usually reveals increased amounts of protein and white blood cells with normal glucose, though in a significant percentage of patients, the cerebrospinal fluid may be normal. Lumbar puncture procedure is performed only after the possibility of prominent brain swelling is excluded by a CT scan examination.
 * Culture of cerebrospinal fluid (CSF), blood, or urine (however, this test is rarely useful)
 * Tests that detect antibodies to a virus (serology tests)
 * Test that detects tiny amounts of virus DNA (polymerase chain reaction-- PCR)

Herpes simplex virus

 * Culture - Herpetic lesion, CSF
 * Tzanck smear

Bacteria

 * Blood culture

Arbovirus

 * Complement fixation antibodies

Epstein-Barr virus

 * Heterophile antibody & cold agglutinin test

Serological test

 * For antibody detection