Cerebrospinal Fluid (CSF) Cryptococcal Antigen Measurement
This test checks for the presence of cryptococcal antigen, a fungal marker, in your cerebrospinal fluid (CSF). It helps diagnose cryptococcal meningitis, a serious infection caused by the fungus *Cryptococcus neoformans*.
["This test can help identify fungal infections in the brain and spinal cord."]
Key facts at a glance
- LOINC
- 22173-9
- Short code
- C pneum IgM Titr CSF
- Synonyms
- C pneum IgM Titr CSF
- Category
- chemistry
- Sample
- csf
- Container
- Sterile tube
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82784
- Specimen volume
- 1-2 mL
- Stability
- Immediate analysis required, Refrigerated: 1h
- Hemolysis max
- 200
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order this test if you have symptoms like severe headaches, neck stiffness, confusion, or fever, especially if you have a weakened immune system or have been exposed to the fungus. It’s also used in monitoring people with HIV/AIDS or other conditions where cryptococcal meningitis is a risk.
What Does the Test Involve?
A small amount of your CSF is collected through a procedure called a lumbar puncture (spinal tap). The sample is then tested for cryptococcal antigen using a sensitive immunoassay method. Results are qualitative (positive or negative) rather than quantitative.
What Are Possible Results?
A positive result means the presence of cryptococcal antigen, which strongly suggests cryptococcal meningitis. A negative result means no detectable antigen, but it doesn’t rule out infection in all cases. Follow-up testing or additional evaluation may be needed.
What Does This Test Tell You About My Health?
A positive result is critical for diagnosing cryptococcal meningitis, guiding treatment decisions, and monitoring response to antifungal medications. It helps doctors determine if you need immediate medical intervention or ongoing care.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Cryptococcal antigen in CSF is a key diagnostic marker for cryptococcal meningitis, particularly in immunocompromised individuals. Early detection improves treatment outcomes and reduces complications. While negative results may initially suggest absence of infection, further evaluation is often required to confirm or rule out other causes of symptoms.
Short name
Cryptococcal Antigen (CSF)
Frequently asked questions
What does a positive result mean for my health?
How often will I need this test if I have a positive result?
Can I take anything to prepare for this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 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