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Serum or Plasma Immunoassay for C-Reactive Protein (CRP)

Published: August 9, 2026Updated: August 16, 2026

This test measures the level of C-reactive protein in your blood. CRP is a protein produced by your liver in response to inflammation.

Quick summary

["CRP helps identify inflammation in your body, which can signal infections, injuries, or other health conditions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
40555-5
Short code
CD66e
Synonyms
CD66e Ag Tiss Ql ImStn
Category
chemistry
Sample
serum
Container
10% neutral buffered formalin container for tissue fixation; paraffin block for processed tissue; fresh tissue in sterile container if requested for special protocols.
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
immune-stain
CPT
88342
SNOMED
104176003
Specimen volume
Tissue specimen of adequate size (minimum 0.5 cm) to allow proper fixation, processing, and sectioning. Adequate tissue required for multiple immunostains and controls.
Stability
Formalin-fixed tissue stable indefinitely at room temperature in properly sealed container. Paraffin-embedded tissue blocks stable for years when stored at room temperature. Cut sections on slides stable for 1-2 weeks at room temperature; longer storage at 2-8°C recommended.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
24–72 hours
Order
routine

What Is CRP Used For?

CRP is often used to monitor conditions like infections (e.g., pneumonia, urinary tract infections), autoimmune diseases (e.g., rheumatoid arthritis), and to check for signs of inflammation after surgery or trauma. It can also help assess risk for heart disease or other chronic inflammatory conditions.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The blood is then sent to a lab where it is analyzed using an immunoassay method to detect CRP levels.

Why Might You Need This Test?

Your healthcare provider may order this test to check for inflammation, diagnose certain conditions, or monitor treatment progress. It can also be used in screening for conditions like heart disease or to evaluate responses to treatments.

What Are Common Results and Next Steps?

Results can vary widely depending on your health status. Elevated CRP levels may indicate inflammation, while normal levels suggest minimal or no inflammation. Your provider will discuss results and next steps based on your specific situation.

Reference range

Reported as Positive or Negative for CD66e (CEA) antigen expression. Reference range: Negative (no specific staining observed in target cells). Positive staining indicates presence of CD66e antigen expression in tissue. Staining intensity and distribution pattern are reported semi-quantitatively (e.g., focal vs. diffuse, weak/moderate/strong intensity).N/A

Specimen: serum

No specific patient preparation required for this tissue-based immunohistochemical test. Specimen collection is performed during surgical procedure or biopsy by qualified healthcare provider.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP Level

Frequently asked questions

What does a high CRP level mean?
A high CRP level often suggests inflammation in your body, which could be due to infections, injuries, autoimmune diseases, or other health problems. Your doctor will review the results along with your medical history and symptoms to determine the cause and next steps.
How often should I get this test?
The frequency of this test depends on your health condition and why it was ordered. Your healthcare provider will let you know how often you need it, whether it’s part of routine check-ups, monitoring a specific condition, or after a particular event like surgery.
Can CRP levels change with diet or lifestyle?
Yes, lifestyle factors like diet, exercise, and smoking can influence CRP levels. Reducing inflammation through healthy habits, such as a balanced diet and avoiding smoking, may help lower CRP levels over time. Always discuss lifestyle changes with your doctor before making significant adjustments.
  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 16, 2026. · Read our editorial policy