Cryptococcal Antigen (Serum/Plasma) - Quantitative
This test measures the presence of cryptococcal antigen, a fungal marker often found in the blood or body fluids of people infected with Cryptococcus neoformans, a type of yeast that can cause serious infections in the lungs or brain.
["A positive result may indicate cryptococcal meningitis or other infections requiring medical evaluation."]
Key facts at a glance
- LOINC
- 100869-7
- Short code
- Crypto gp60 Spec
- Synonyms
- Crypto gp60 Spec
- 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
- molgen
- 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 Is Done
Doctors may order this test if you have symptoms like fever, headache, confusion, or weakness, especially if you have a weakened immune system (e.g., from HIV/AIDS, chemotherapy, or organ transplant). It’s also used to monitor people already diagnosed with cryptococcal meningitis to check for disease progression or response to treatment.
What to Expect Before the Test
No special preparation is needed. You’ll have a small needle inserted into a vein in your arm, and a blood sample will be drawn. The test is quick and typically done in a lab setting.
What the Results Mean
Results are reported as either positive or negative. A positive result suggests the presence of cryptococcal antigen, which may need further testing or medical intervention. A negative result means no detectable antigen was found, but this doesn’t rule out infection completely.
Possible Causes of Positive Results
Positive results are most commonly linked to cryptococcal meningitis or other cryptococcal infections. Rarely, false positives can occur, especially in people with certain medical conditions or medications that affect lab tests.
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.
Clinical Significance
Short name
Crypto Ag (Serum/Plasma)
Frequently asked questions
If you have a weakened immune system or symptoms like those mentioned above, this test helps doctors diagnose or monitor cryptococcal infections early, which is critical for treatment and preventing complications.
If you have a negative result but still have symptoms, your doctor may recommend additional tests or repeat the test later to rule out other infections or conditions.
How often will I need 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