CRP or C-reactive protein is a substance that has considerable importance in diagnostics of many diseases. In infectious conditions, it is an important indicator that tells us whether to use antibiotics or not.


The CRP is a protein produced by the liver tissue that belongs among so-called acute phase proteins. The serum concentration of these proteins rises when our body is affected by inflammatory processes. Given the fact that our body reacts with inflammatory response practically to all foreign or harmful factors, the finding of elevated acute phase proteins is quite common. Elevated CRP can be found in three major groups of illnesses – infections, malignant diseases and autoimmune diseases.


The advantage is the high sensitivity of CRP. Normal blood level in a healthy person is usually below 6 milligrams per liter. Significant inflammation causes its elevation to tens or hundreds milligrams per liter. Another advantage is a relative speed of CRP elevation, which may be increased within hours after the onset of symptoms.


In infectious diseases, the CRP value of 6-40 mg per liter rather corresponds to viral infection, while CRP value greater than 40 mg per liter is more common for bacterial infections.


If the patient visits a doctor with a fever and other signs of infection, we ar usually interested whether to prescribe antibiotics. Antibiotics are ineffective against viral infections and their excessive prescription can lead to local increase of bacterial resistance to antibiotics. The CRP is a great solution as its concentration can be evaluated from a minimal blood sample within minutes.


When we treat an infection by antibiotics, we repeatedly check the CRP level to evaluate the effect of antibiotic therapy. Fast and significant drop of CRP means successful therapy.


The CRP may be also a warning sign of any non-infectious pathological process in the body. Tens or even hundreds mg per liter may accompany autoimmune diseases or malignant diseases with metastatic spread.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources