C-reactive protein (CRP) by nephelometry
This test measures the level of C-reactive protein in your blood, a protein produced by your liver in response to inflammation or infection.
["CRP helps doctors assess inflammation, infection, or other health issues."]
Key facts at a glance
- LOINC
- 102789-5
- Short code
- CAYIGG
- Synonyms
- Cayenne IgG RAST
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum tube or serum separator tube (SST)
- Units
- N/A
- Ref low
- 0
- Ref high
- 6
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 1 years
- Method
- Radioallergosorbent test (RAST) - Immunoassay detecting allergen-specific IgG antibodies
- CPT
- 86001
- SNOMED
- 395147008
- Specimen volume
- 1 mL serum (minimum 0.5 mL)
- Stability
- Serum stable at room temperature for 8 hours, refrigerated at 2-8°C for 7 days, or frozen at -20°C for up to 30 days. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 100
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 24–72 hours
- Order
- routine
Why Is This Test Done?
Doctors may order CRP testing to monitor conditions like infections (e.g., pneumonia, urinary tract infections), inflammatory diseases (e.g., rheumatoid arthritis, lupus), or to check for signs of heart disease or other systemic issues. It can also help track how well treatment is working for certain conditions.
What Does a High or Low CRP Level Mean?
A higher-than-normal CRP level often signals inflammation or infection. A very high level may indicate severe infection or conditions like sepsis. A low level usually means little to no inflammation is present, but it doesn’t rule out all causes of inflammation. Your doctor will interpret results in the context of your symptoms and other tests.
How Is the Test Performed?
A blood sample is taken from a vein, usually in your arm. The blood is sent to a lab where it is analyzed using a specialized machine to measure CRP levels.
What Are Common Causes of Abnormal CRP Levels?
Increased CRP levels can be caused by infections, injuries, surgeries, autoimmune diseases, or certain medications. Low CRP levels may occur in people with very mild inflammation or those who are generally healthy without active inflammatory conditions.
Reference range
Negative (IgG antibodies to cayenne pepper not detected). Results reported as positive or negative based on class scoring (Class 0-6).N/A
No fasting required. No special patient preparation necessary. Inform clinician of any antihistamine or immunosuppressive medication use as these may affect results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
CRP plays a key role in identifying and managing conditions involving inflammation. It can be a useful marker for early detection of infections, monitoring chronic inflammatory diseases, or evaluating the risk of cardiovascular events in some patients. However, CRP alone is not diagnostic for any specific condition and should be used alongside other clinical findings.
Short name
CRP
Frequently asked questions
What does a CRP test measure?
How often should I get a CRP test?
Can CRP levels change with diet or exercise?
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 17, 2026. · Read our editorial policy