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Tbevigaindexsercsfacnc

Published: August 9, 2026Updated: August 16, 2026

This test measures IgA antibodies against tick-borne encephalitis virus in both blood and spinal fluid to determine if the infection is affecting the central nervous system.

Quick summary

{"Detects IgA antibodies specific to tick-borne encephalitis virus","Compares antibody levels in blood (serum) and cerebrospinal fluid (CSF)","Helps confirm if the virus has infected the brain or spinal cord","The antibody index indicates local production of antibodies within the central nervous system","Sample is collected from both blood and spinal fluid"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
104393-4
Short code
TBEV IgA
Synonyms
TBEV IgA index Ser+CSF-aCnc
Category
cardiac
Sample
serum
Container
Serum separator tube (SST) or plain red top tube
Units
N/A
Ref low
1.1
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Enzyme-linked immunosorbent assay (ELISA)
CPT
86635
SNOMED
371949004
Specimen volume
1-2 mL serum
Stability
Refrigerated (2-8°C): up to 7 days; Frozen (-20°C or below): up to 30 days
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
72–168 hours
Order
routine

What is this test?

The European tick-borne encephalitis virus IgA antibody index test is a specialized laboratory test that helps doctors determine if the tick-borne encephalitis virus has infected your central nervous system (brain and spinal cord). The test measures IgA antibodies in both your blood (serum) and the fluid surrounding your brain and spinal cord (cerebrospinal fluid or CSF). By comparing these two measurements, doctors can tell if your body is producing antibodies specifically within your central nervous system, which is a key indicator of neurological involvement.

How does the antibody index work?

When your immune system encounters the tick-borne encephalitis virus, it produces specific antibodies to fight the infection. If the virus reaches your central nervous system, your immune system produces these antibodies directly within the brain and spinal cord. The antibody index compares the concentration of IgA antibodies in your CSF to their concentration in your blood. A high index value suggests that antibodies are being produced locally within your central nervous system, confirming that the infection has spread to your nervous system.

What is tick-borne encephalitis?

Tick-borne encephalitis (TBE) is a viral infection transmitted through the bite of infected ticks, primarily found in parts of Europe and Asia. While many people experience mild symptoms, the virus can sometimes spread to the central nervous system, causing inflammation of the brain (encephalitis) or membranes surrounding the brain and spinal cord (meningitis). Severe cases can lead to long-term neurological complications. The TBE virus is endemic in many forested regions of Central and Eastern Europe.

How is the sample collected?

This test requires two different samples. A blood sample is drawn from a vein in your arm, similar to a routine blood test. Cerebrospinal fluid is collected through a procedure called a lumbar puncture (spinal tap), where a thin needle is inserted into the lower back to withdraw fluid from the space surrounding the spinal cord. Both samples are then sent to a laboratory where the IgA antibody levels are measured and the index is calculated.

Reference range

Index <1.1: Negative for IgA antibodies; 1.1-1.4: Equivocal; ≥1.4: Positive for IgA antibodiesN/A

Specimen: serum

No special preparation required. Patient may eat and drink normally before sample collection.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings2

Frequently asked questions

Why do I need both blood and spinal fluid samples?
Comparing antibodies in both samples is essential because it allows doctors to determine if the antibodies in your spinal fluid are being produced locally within your central nervous system (intrathecal synthesis) or if they simply leaked from your blood. This distinction is critical for confirming that the virus has actually infected your brain or spinal cord, rather than just being present in your bloodstream.
Is a lumbar puncture painful?
A lumbar puncture (spinal tap) is performed with local anesthesia, so you may feel some pressure or discomfort but significant pain is uncommon. The procedure is generally safe and takes only a few minutes. You may experience a mild headache afterward, which can usually be managed with rest and hydration. Your healthcare provider will explain the procedure in detail and address any concerns before the test.
What do the results mean?
A high antibody index value (typically above 1.5 or as defined by the laboratory) suggests that IgA antibodies against TBE virus are being produced within your central nervous system, indicating neuroinvasive TBE. A low or negative index suggests that any detected antibodies likely came from the bloodstream and may not indicate CNS involvement. Your doctor will interpret your results in the context of your symptoms, physical examination, and other test findings.
How long does it take to get results?
This is a specialized test that is not performed at all laboratories. Samples often need to be sent to a reference laboratory with specialized expertise. Results typically take several days to a week or more, depending on where the testing is performed. Your healthcare provider will inform you when results are available and discuss them with you.
Do I need to fast before this test?
Fasting is not typically required for this test. However, you should follow any specific instructions provided by your healthcare provider. For the blood sample, you can usually eat and drink normally before the test. The lumbar puncture preparation may have specific instructions that your doctor will explain.
  1. 1
    Centers for Disease Control and Prevention (CDC) - Tick-borne EncephalitisSource
  2. 2
    European Centre for Disease Prevention and Control (ECDC) - Tick-borne EncephalitisSource
  3. 3
    Mayo Clinic Laboratories - Tick-borne Encephalitis Virus Antibody, IgG and IgM, Serum and CSFSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy