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Serum/plasma concentration of C-reactive protein (CRP) measured by nephelometry

Published: August 9, 2026Updated: August 15, 2026

This test measures the level of C-reactive protein, a protein produced by the liver in response to inflammation or infection in your body.

Quick summary

["CRP helps doctors assess inflammation, track infections, or evaluate risk for conditions like heart disease."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
5097-1
Short code
COLDAGG
Synonyms
CA SerPl Ql Aggl
Category
chemistry
Sample
serum
Container
Red-top serum tube (no anticoagulant) or serum separator tube (SST). Avoid EDTA tubes as anticoagulants may interfere with agglutination patterns.
Units
N/A
Ref low
0
Ref high
1
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
Agglutination (Qualitative detection of cold-reactive autoantibodies at 4°C)
CPT
86157
SNOMED
3953-8
Specimen volume
3-5 mL of whole blood (yielding approximately 1-2 mL of serum)
Stability
Serum should be separated from clotted blood and kept at 37°C. Testing should be performed as soon as possible, ideally within 2 hours of collection. If delayed, serum can be stored at 4°C for up to 24 hours, but must be rewarmed to 37°C before testing.
Hemolysis max
50
Lipemia max
100
Icterus max
20
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may order this test to monitor inflammation, check for infections (such as bacterial infections), or evaluate conditions like autoimmune diseases, heart disease, or kidney problems. It can also be used to monitor treatment responses for certain conditions.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it’s part of a broader panel, but this depends on the lab’s instructions. Bring any medications you’re taking to your appointment.

What the Test Involves

A healthcare professional will draw blood from a vein in your arm. You may feel a brief pinch or slight discomfort, but it’s usually over quickly. The blood sample is then sent to the lab for analysis.

What the Results Mean

Higher-than-normal CRP levels may indicate inflammation, infection, or other health issues. Your results will be compared to your healthcare provider’s expectations based on your medical history and symptoms. They’ll discuss the meaning with you.

Reference range

Negative (No cold agglutinins detected at 1:64 or higher dilution). Titer <1:64 is generally considered clinically insignificant.N/A

Specimen: serum

No special preparation required. Specimen should be kept at 37°C during collection and transport to prevent in vitro cold agglutinin adsorption onto red blood cells, which may cause false-negative results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CRP is a marker of acute-phase reactant, meaning its levels rise in response to inflammation or injury. Elevated CRP can signal infections (e.g., pneumonia, urinary tract infections), autoimmune diseases (e.g., rheumatoid arthritis), or chronic conditions like heart disease. It’s also used to monitor disease activity or treatment progress in some cases.

Short name

CRP (Serum/plasma)

Frequently asked questions

What does a high CRP level mean?
A high CRP level often suggests inflammation or infection in your body. Your doctor will consider your symptoms, medical history, and other test results to determine the cause. Common causes include infections, autoimmune diseases, or conditions like heart disease.
What if my CRP level is normal?
A normal CRP level means your body isn’t showing significant inflammation at this time. However, it doesn’t rule out all possible causes of inflammation. Your doctor may still recommend follow-up tests or monitoring if you have ongoing symptoms or risk factors.
Can CRP levels change over time?
Yes, CRP levels can fluctuate based on your health status, recent infections, medications, or other factors. If your CRP is elevated, your doctor may retest it later to see how it changes or to guide treatment decisions.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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 15, 2026. · Read our editorial policy