Skip to content

C-reactive protein (CRP) by turbidimetry

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

This test measures the level of C-reactive protein in your blood, which is a marker of inflammation. It helps doctors assess whether you have an ongoing inflammatory condition or response to infection.

Quick summary

["CRP helps track inflammation, guiding treatment decisions and monitoring chronic conditions."]

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

Key facts at a glance

LOINC
99406-1
Short code
CD19CD79b
Synonyms
Cells.CD19+CD79b+ NFr Bld
Category
chemistry
Sample
whole-blood
Container
EDTA (lavender/purple-top) or sodium heparin (green-top) blood collection tube; ACD (yellow-top) tubes are also acceptable for immunophenotyping.
Units
N/A
Ref low
5
Ref high
15
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Flow cytometry using fluorescently labeled monoclonal antibodies against CD19 (pan-B-cell marker) and CD79b (B-cell receptor component). Cells are identified by dual-positive fluorescence emission detected via multiparameter flow cytometric analysis.
CPT
86356 (Monoclonal antibody, quantitative), 88184 (Flow cytometry, cell surface, cytoplasmic) or 88185 (additional marker)
SNOMED
1421000119104 | Measurement of B-lymphocyte count (procedure); 145391000119102 | B-lymphocyte number (observable entity)
Specimen volume
3-5 mL of whole blood for adults; minimum 1 mL for pediatric specimens. Higher volumes preferred for absolute count accuracy.
Stability
Specimen should be processed within 24 hours of collection when stored at room temperature (18-22°C). Refrigeration (2-8°C) may extend stability to 48 hours for some markers but can affect cell viability and fluorescence intensity. Samples should not be frozen.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What Is C-Reactive Protein?

C-reactive protein (CRP) is a protein produced by your liver in response to inflammation. It rises when your body fights infection, injury, or other inflammatory processes. While CRP itself isn’t harmful, its presence signals that your immune system is active.

Why Might Your Doctor Order This Test?

Doctors may order CRP tests to evaluate symptoms like fever, joint pain, or unexplained swelling. It’s also used in screening for conditions like heart disease, autoimmune disorders, or infections. Some tests may check CRP levels before surgery or to monitor chronic conditions like rheumatoid arthritis.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed using a turbidimetric method to measure CRP levels. The process is quick and typically requires no special preparation.

What Do Results Mean?

Results are reported in milligrams per deciliter (mg/dL). Higher levels may indicate inflammation, infection, or other health issues. Your doctor will interpret results based on your symptoms, medical history, and other tests.

Reference range

Reference ranges vary by laboratory, instrument, and antibody clone. Absolute count typically reported as cells/μL; relative percentage as % of total lymphocytes or leukocytes. Adult reference intervals are generally established locally; published studies suggest CD19+CD79b+ B-cell populations constitute approximately 5-15% of peripheral blood lymphocytes in healthy adults. Pediatric values may differ.N/A

Specimen: whole-blood

No special patient preparation required. Recent immunosuppressive therapy, chemotherapy, corticosteroid use, or B-cell-targeted biologics (rituximab, obinutuzumab) may significantly alter results and should be documented. Specimen should be processed within 24 hours of collection for optimal viability.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

CRP Blood Test

Frequently asked questions

How often should I get this test?
The frequency depends on your health condition. For example, people with heart disease or autoimmune disorders may get CRP tests regularly, while others might only need it if symptoms arise or for specific reasons like pre-surgery screening.
Can I eat or drink before this test?
No special preparation is needed for this test. However, if your doctor instructed otherwise (e.g., fasting for other tests), follow their guidance. Drinking water is fine unless specified.
What if my CRP levels are high?
High CRP levels may prompt further testing or treatment to address the underlying cause, such as infections, autoimmune conditions, or other inflammatory diseases. Your doctor will discuss next steps with you.
  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