CRP (C-Reactive Protein) Test

Normal results

In healthy individuals, there is less or almost no CRP. The normal levels of CRP in the serum are 0-6 milligrams per litre (mg/L). These values indicate an absence of acute infection or inflammation.

However, for a hs-CRP test, a concentration of 3 mg/L may also be considered high risk for cardiovascular diseases.

Abnormal results

• A higher concentration of CRP of >4 mg/L to 100 mg/L suggest conditions, such as active SLE, RA, viral infections, tumours and myeloma.
• Moderate concentrations between 100-200 mg/L indicate active RA, polymyalgia, lymphoma and bacterial infection.
• Highly elevated concentrations of CRP of >200 mg/L suggest bacterial sepsis and acute vasculitis.
• A concentration of more than 400 mg/L is an indication of deep tissue abscess, and death may occur in such cases.

Hs-CRP is an independent marker of cardiovascular diseases. For the hs-CRP marker, patients can be grouped into various risk groups depending on their hs-CRP levels:

• Low-risk group: less than 1 mg/L,
• Moderate-risk group: 1-3 mg/L
• High-risk group: more than 3 mg/L.

CRP concentrations are not only indicators of certain diseases but can also be used to differentiate certain symptoms. Determination of CRP level can help in the following ways:

• Detect chronic and systemic inflammation
• Monitor antibiotic treatment for bacterial infections
• Differentiate concurrent infections, such as those due to SLE or ulcerative colitis
• Assess all rheumatic conditions and decide treatment modalities for inflammatory conditions
• Detect postoperative complications such as infections
• Detect a risk of cardiovascular diseases through hs-CRP
• Predict the presence of tumours

CRP concentration ranges mentioned above may differ according to the method of analysis used and the laboratory in which the test is performed.

Conclusively, CRP is an important indicator of acute infections and chronic and acute inflammatory conditions; It also helps in the diagnosis of cardiovascular diseases and requires regular monitoring in heart patients. Depending on the health of the patient, a CRP test should be followed by other important laboratory investigations for diagnosing the condition accurately and deciding the correct line of treatment.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. This information is provided from a purely educational perspective and is in no way a substitute for medical advice from a qualified doctor.  

The test requires only a few millilitres of blood sample. A skilled laboratory technician will clean your skin with an antiseptic, insert a needle in the arm, draw a blood sample in a pre-sterilised tube or vial and send it for analysis. The procedure is simple and painless, although patients may occasionally experience pain at blood withdrawal site.

CRP test is a simple blood test and does not require any special preparation. The test can be carried out anytime, and fasting is usually not necessary. Fasting may be preferred in some cases, though the patient may be allowed to drink water.

CRP is almost absent in healthy individuals. It is a very sensitive reactant to acute-phase infections and inflammatory processes. Inflammatory substances, such as interleukin (IL)-1 and IL-6, are responsible for the increased secretion of CRP by macrophages involved in the inflammatory processes. Higher CRP levels accurately point at the presence of infection and inflammation. Presence of hs-CRP is an indicator of myocardial infarction, and it can be a predictor of paediatric coronary heart disease. Following are the conditions in which a CRP test is prescribed by a doctor:

• Autoimmune inflammatory diseases, such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE)
• Acute infections, such as meningitis, cerebral abscess and viral encephalitis
• To check for prognosis in patients with atherosclerotic disease, congestive heart failure, atrial fibrillation, myocarditis, aortic valve disease and heart transplant
• Neonatal sepsis and conditions, such as appendicitis, pancreatitis and other inflammatory conditions
• Monitoring dosage regimen for disease-modifying anti-rheumatic drugs (DMARDs) and antibiotics
• Myalgia and osteomyelitis
• Cancers of the lung, breast and kidney
• Trauma