Complete Blood Count (CBC) Test
A laboratory test that detects bacterial antigens in cerebrospinal fluid to help diagnose infections of the brain and spinal cord.
{"This test checks for signs of bacterial infection in the fluid surrounding your brain and spinal cord","It helps doctors diagnose serious conditions like bacterial meningitis quickly","A sample of cerebrospinal fluid is collected via a lumbar puncture (spinal tap)","Results can guide immediate treatment with antibiotics","The test is often done alongside other CSF tests for a complete picture"}
Key facts at a glance
- LOINC
- 43131-2
- Short code
- BACTAGCSF
- Synonyms
- Bacterial Ag Pnl CSF
- Category
- chemistry
- Sample
- csf
- Container
- Sterile, leak-proof CSF collection tubes (polypropylene or polystyrene); screw-cap cryovial preferred for antigen stability
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- Latex agglutination assay; immunochromatographic test; enzyme immunoassay (EIA); polymerase chain reaction (PCR) depending on target organism
- CPT
- 87147
- SNOMED
- 104345000
- Specimen volume
- 1-2 mL of CSF per tube; minimum 0.5 mL acceptable for individual antigen testing; multiple tubes recommended (Tube 3 or 4 preferred for microbiology to minimize skin contamination)
- Stability
- Room temperature: 1-2 hours; refrigerated (2-8°C): up to 24 hours; frozen (-20°C or below): up to 7 days for antigen testing; do not repeatedly freeze-thaw
- Hemolysis max
- 200
- TAT
- 1–4 hours
- Order
- routine
What is this test?
The Bacterial Antigen Panel (CSF) is a laboratory test that looks for specific bacterial antigens (substances that trigger an immune response) in your cerebrospinal fluid (CSF). CSF is the clear, protective fluid that surrounds your brain and spinal cord. This test helps doctors quickly identify if a bacterial infection is present in the central nervous system.
Why might my doctor order this test?
Your doctor may order this test if you have symptoms suggesting a serious brain or spinal cord infection, such as severe headache, stiff neck, high fever, confusion, or sensitivity to light. It is commonly used when bacterial meningitis is suspected. The test provides rapid results, helping doctors start the right treatment without delay.
How is the sample collected?
The sample is collected through a procedure called a lumbar puncture, also known as a spinal tap. A healthcare provider inserts a thin needle into the lower back to withdraw a small amount of cerebrospinal fluid. The area is numbed first to minimize discomfort. The fluid is then sent to a laboratory for analysis.
What do the results mean?
A positive result indicates that bacterial antigens were detected in your CSF, suggesting a bacterial infection of the central nervous system, such as bacterial meningitis. A negative result means no bacterial antigens were found, but it does not completely rule out infection—your doctor will consider your symptoms and other test results. Common bacteria detected include Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, and Group B Streptococcus.
Are there any risks with this test?
The lumbar puncture is generally safe, but some people may experience headache, back pain, or minor bleeding. Serious complications like infection or nerve damage are rare. Your healthcare team will take precautions to minimize risks.
Reference range
Negative for all bacterial antigens tested (including but not limited to: Streptococcus pneumoniae, Neisseria meningitidis groups A/C/Y/W-135, Neisseria meningitidis group B, Haemophilus influenzae type b, Group B Streptococcus, Escherichia coli K1). Positive results should be confirmed by culture.N/A
No fasting required. Specimen collection by lumbar puncture is an invasive procedure requiring informed consent. Aseptic technique is mandatory to prevent contamination and iatrogenic meningitis.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The Bacterial Antigen Panel is critical for the early diagnosis of bacterial meningitis and other central nervous system infections. Rapid identification of the causative bacteria allows doctors to start targeted antibiotic therapy immediately, which can be life-saving. This test is especially valuable when culture results are pending or when the patient has already received antibiotics, which can affect culture results. It helps distinguish between bacterial and viral infections, guiding appropriate treatment and avoiding unnecessary antibiotic use for viral conditions.
Frequently asked questions
How long does it take to get results?
Do I need to fast before this test?
Is the lumbar puncture painful?
Can this test detect all types of bacteria?
What happens after a positive result?
Sources
- 1
- 2Mayo Clinic - MeningitisSource
- 3
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.
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