C-reactive protein (CRP) by nephelometry (serum/plasma)
This test measures the level of C-reactive protein, a protein produced by the liver in response to inflammation in your body.
["CRP helps doctors check for inflammation, which can signal infections, injuries, or other health issues."]
Key facts at a glance
- LOINC
- 14658-9
- Short code
- COLDAG
- Synonyms
- CA Titr SerPl
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum tube (no anticoagulant) or serum separator tube (SST); EDTA plasma acceptable but serum preferred. Pre-warmed tubes (37°C) recommended to preserve cold agglutinin reactivity.
- Units
- N/A
- Ref low
- 0
- Ref high
- 1
- Critical range
- — – 512 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Agglutination assay (serial dilution titration at 4°C with subsequent warming to 37°C to confirm cold-reacting antibody specificity)
- CPT
- 86157
- SNOMED
- 398900000
- Specimen volume
- 1-2 mL serum (minimum 0.5 mL)
- Stability
- Sample must be maintained at 37°C during collection and transport. Once separated, serum is stable for 24 hours at 2-8°C. For prolonged storage, freeze at -20°C or below for up to 7 days. Do not refrigerate whole blood as cold agglutinins may bind to RBCs and yield false-negative results.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
Why This Test Is Done
Your healthcare provider may order this test to monitor conditions like infections, autoimmune diseases, or after surgery to track healing. It can also help assess risk for heart disease or other inflammatory conditions.
What to Expect Before the Test
No special preparation is needed. You may have a small needle inserted into your arm to draw blood. If you’re on blood thinners, let your provider know before the test.
What the Results Mean
Higher CRP levels often indicate inflammation, but results alone don’t diagnose a specific condition. Your provider will review them alongside other factors like symptoms and medical history.
Common Conditions Monitored
Elevated CRP is commonly seen in infections (like pneumonia or urinary tract infections), after trauma or surgery, or in conditions like rheumatoid arthritis or heart disease.
Reference range
Negative or titer <1:32 (normal); Titer ≥1:64 may be clinically significant and suggestive of cold agglutinin disease, Mycoplasma pneumoniae infection, or other cold-reactive autoimmune hemolytic conditionsN/A
No special patient preparation required. Specimen should be collected and maintained at 37°C to prevent in vitro cold agglutinin adsorption and false-negative results. Avoid cooling of sample during transport and processing.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
CRP (Nephelometry)
Frequently asked questions
What causes CRP levels to rise?
How often should I get this test?
Can diet or exercise affect CRP levels?
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