Cryptosporidium Antigen, Qualitative, Stool
This test looks for antigens (protein markers) from the parasite Cryptosporidium in a stool sample to help determine whether it is causing diarrhea or other digestive symptoms.
["A positive result supports Cryptosporidium infection, while a negative result makes it less likely but does not rule it out entirely."]
Key facts at a glance
- LOINC
- 51911-6
- Short code
- G lamblia+Cryptosp Ag sp3 Stl Ql
- Synonyms
- G lamblia+Cryptosp Ag sp3 Stl Ql
- Category
- coagulation
- Sample
- stool
- Container
- Clean container
- 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
- CPT
- 85610
- SNOMED
- 396252006
- Specimen volume
- 5 g
- Stability
- Refrigerated: 24h, Frozen: 7d
- TAT
- 4–24 hours
- Order
- routine
What Is Being Tested
Cryptosporidium is a tiny parasite that can infect the intestines and cause watery diarrhea. This test detects pieces of the parasite (antigens) shed in stool, which can appear even when the organism is hard to see under a microscope.
How the Sample Is Collected
You provide a stool sample, typically collected at home or in a healthcare setting using a clean container supplied by the laboratory. Follow the collection instructions carefully and return the sample promptly, since some tests require fresh or specially preserved stool.
What a Positive Result Means
A positive result suggests that Cryptosporidium antigens are present and that the parasite may be causing your symptoms. Your clinician will interpret this together with your history, symptoms, and possibly other stool tests.
What a Negative Result Means
A negative result means the test did not detect Cryptosporidium antigens. Because test performance and parasite shedding can vary, a negative result does not always completely exclude infection, and your clinician may recommend repeat or additional testing if suspicion remains.
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.
Cryptosporidium infection can cause self-limited watery diarrhea in healthy people but may be severe or prolonged in young children, older adults, and people with weakened immune systems. Antigen testing supports timely diagnosis, which helps guide hydration, infection-control measures, and, when appropriate, treatment decisions. Results should always be interpreted by a clinician in the context of the patient's symptoms and exposure history.
Short name
Crypto Stool Antigen
Frequently asked questions
Do I need to fast or change my diet before this test?
Can this test tell me which treatment I need?
How is Cryptosporidium usually spread?
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