Skip to content

C-reactive protein (CRP) by nephelometry

Published: August 9, 2026Updated: August 17, 2026

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

Quick summary

["CRP helps doctors assess inflammation, infection risk, or other health conditions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
102210-2
Short code
CATDANDER
Synonyms
Cat Dander IgE RAST
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or red-top tube without anticoagulant
Units
N/A
Ref low
0.35
Ref high
0.7
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
Radioallergosorbent test (RAST) - solid-phase immunoassay using radiolabeled anti-IgE antibodies to detect allergen-specific IgE antibodies in serum
CPT
86003
SNOMED
395127008
Specimen volume
0.5-1 mL serum (minimum 0.3 mL)
Stability
Stable for 7 days at 2-8°C; for longer storage, freeze at -20°C or below for up to 4 weeks. Avoid repeated freeze-thaw cycles.
Hemolysis max
200
Lipemia max
100
Icterus max
40
TAT
24–72 hours
Order
routine

Why is CRP tested?

Doctors may order CRP testing to monitor conditions like infections (e.g., pneumonia, urinary tract infections), inflammatory diseases (e.g., rheumatoid arthritis), or to check for signs of heart disease or other risks. It can also help guide treatment decisions or track how your body responds to treatment.

What does a CRP result mean?

Higher CRP levels often indicate inflammation or infection, but results vary depending on your health status, symptoms, and medical history. Your doctor will interpret the result in the context of your overall health and other tests.

How is CRP collected?

A blood sample is drawn from a vein, usually in your arm. The blood is sent to a lab where it is analyzed using nephelometry, a method that measures how particles scatter light to detect CRP levels.

What can affect CRP levels?

Several factors can influence CRP levels, including infections, injuries, autoimmune diseases, certain medications, smoking, stress, or recent physical activity. Chronic conditions like heart disease or obesity may also play a role.

Reference range

Negative: <0.35 kU/L (Class 0); Equivocal: 0.35-0.70 kU/L (Class 1); Positive: ≥0.70 kU/L (Classes 2-6). Results reported as positive or negative for the presence of IgE antibodies to cat dander (Felis domesticus).N/A

Specimen: serum

No fasting required. Patients should inform their healthcare provider of any medications, particularly antihistamines, which may not affect in vitro IgE testing but should be noted. Avoid recent allergen exposure documentation if clinically relevant.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CRP plays a key role in identifying and managing conditions tied to inflammation. Elevated CRP can signal areas of concern, prompting further evaluation or treatment adjustments. It’s often used as a screening tool or to monitor disease progression in conditions like cardiovascular disease, where inflammation contributes to plaque buildup.

Short name

CRP (Nephelometry)

Frequently asked questions

What does a high CRP level mean?
A high CRP level may suggest inflammation, infection, or an underlying condition like autoimmune disease. Your doctor will discuss the result with you and may recommend additional tests or treatments based on your symptoms and medical history.
What does a low CRP level mean?
A low CRP level generally indicates minimal inflammation, but it doesn’t rule out all causes of low-grade inflammation. It may be normal if you’re healthy or if your body isn’t responding to an infection or injury.
How often should I get a CRP test?
Your doctor will determine how often you need a CRP test based on your health needs, symptoms, or ongoing conditions. Regular monitoring may be part of managing chronic diseases or assessing risk factors for conditions like heart disease.
  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 17, 2026. · Read our editorial policy