Cryptococcal Antigen (Serum/Plasma) - Quantitative
This test detects the presence of cryptococcal antigen, a fungal marker often found in the blood or serum/plasma of people with cryptococcal meningitis, a serious fungal infection caused by *Cryptococcus neoformans* or *C. gattii*. It’s used primarily in patients with weakened immune systems, such as those with HIV/AIDS or undergoing immunosuppressive therapy.
["A key test for diagnosing cryptococcal meningitis in high-risk patients."]
Key facts at a glance
- LOINC
- 98410-4
- Short code
- Cryptoc Molec Typ Islt Seq
- Synonyms
- Cryptoc Molec Typ Islt Seq
- Category
- coagulation
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- — – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- sequencing
- CPT
- 85610
- SNOMED
- 396252006
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Matters
Cryptococcal antigen testing is critical for diagnosing cryptococcal meningitis, a fungal infection that can be life-threatening. The antigen is released by the fungus during active infection, and detecting it early can guide treatment decisions, including the use of antifungal medications.
How the Test Works
The test measures the concentration of cryptococcal antigen in your blood or serum/plasma using a highly sensitive immunoassay method. It’s typically performed as part of a screening or confirmatory test when clinical symptoms or risk factors (like HIV) are present.
When You Might Need This Test
You may need this test if you have an immune system that doesn’t work well (e.g., HIV/AIDS, organ transplant recipients, or those on chemotherapy), symptoms like fever, headache, confusion, or neurological issues, or if you’ve been exposed to *Cryptococcus* in high-risk environments (e.g., soil or pigeon droppings).
What to Expect Before the Test
No special preparation is needed for this test. A blood sample is drawn from a vein, usually in your arm. The process is quick and typically painless. If you’re on blood-thinning medication, let your healthcare provider know before the test.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
Inform your healthcare provider if you are taking blood thinners. No special preparation required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Crypto Ag (Serum/Plasma)
Frequently asked questions
What does a positive result mean?
Can this test be done at home?
How often should I get this test if I have HIV or a weakened immune system?
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