A protein that rises rapidly when there is inflammation or infection in the body. Frequently used in the diagnosis and treatment monitoring of acute illnesses.
Indication
- Suspected bacterial infection and monitoring of treatment response
- Evaluation of sepsis and systemic infection
- Monitoring inflammatory rheumatic diseases such as rheumatoid arthritis and ankylosing spondylitis
- Monitoring activity of inflammatory bowel disease (Crohn's disease, ulcerative colitis)
- Early detection of postoperative infection
- Supportive parameter in the differential diagnosis of febrile illnesses
- Cardiovascular risk assessment using high-sensitivity CRP (hsCRP)
Preparation
- No special preparation is generally required, and fasting is not necessary
- Medications used (especially NSAIDs and steroids) should be reported to the physician
- Acute illness or recent vaccination may affect the results
- Conditions such as pregnancy and obesity may influence interpretation of the reference range
How it's performed
- A venous blood sample is drawn from the arm (typically 2-3 mL)
- The blood is placed in a biochemistry tube and sent to the laboratory
- Measurement is performed using immunoturbidimetric or nephelometric methods on modern automated analyzers
- The result is reported in mg/dL or mg/L
- For high-sensitivity CRP (hsCRP), the same blood sample is processed using a more sensitive method
Post-procedure
- Results are typically ready within a few hours
- In acute infections, CRP should decrease noticeably within 2-3 days after treatment is started
- The physician may request periodic CRP follow-up during treatment monitoring
- Mild tenderness or a small bruise at the blood draw site resolves spontaneously
Risks
- Temporary pain or mild bruising at the blood draw site
- Rare small hematoma
- Dizziness related to the needle (vasovagal reaction, rare)
- Very rarely, local infection at the needle site
FAQ
What is a normal CRP value?
In most laboratories, values below 0.5 mg/dL (5 mg/L) are interpreted as low inflammation. Different thresholds are used to interpret cardiovascular risk with high-sensitivity CRP (hsCRP).
What does an elevated CRP mean?
It indicates that there is inflammation or infection in the body, but does not show the cause. Bacterial infections generally cause higher elevations, while viral infections may cause more limited increases.
What is the difference between CRP and ESR (sedimentation rate)?
CRP responds to inflammation more rapidly and returns to normal more quickly. ESR changes more slowly; evaluating both together provides information about the course of the condition.
How long does the test take to result?
In most hospital laboratories, CRP results are obtained within 1-3 hours. In emergency departments, results may be available even sooner.
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