CRP is a substance synthesized by the liver and actively involved in triggering immune responses. CRP is an indicator of inflammation, tissue injury, or necrosis.
It is used in the diagnosis of inflammatory processes of various locations. CRP should be tested in conjunction with a complete blood count and other acute-phase reactants. CRP levels help the physician determine the disease activity and decide on further treatment.
C-reactive protein (CRP) – is a protein produced by liver cells (hepatocytes) in response to inflammation. Its blood levels rise rapidly in the presence of infections, tissue damage, or necrosis (tissue death).
CRP plays a vital role in the body's defenses – it helps the immune system recognize and neutralize harmful microorganisms and activates processes that promote their destruction. This is why its elevation is considered a universal indicator of inflammation. C-reactive protein levels begin to rise within 6-12 hours of the onset of inflammation and can increase tens or even hundreds of times. After the cause of the inflammation is eliminated, CRP concentrations also decrease rapidly. This indicator is therefore used not only to detect inflammation but also to monitor the progression of the disease and assess the effectiveness of treatment.
Its main function is to activate immune responses. CRP consists of five identical subunits, non-covalently linked, and has several specific sites for both binding to membrane components of damaged cells and binding to receptors. Clq is a complement component. CRP is a proinflammatory trigger, as it stimulates monocyte production of IL-1, IL-6, and TNF-α. Increased CRP is a nonspecific response to inflammatory and infectious processes.
CRP testing is used to:
- identify acute and chronic inflammatory processes;
- monitor the progression of infectious and autoimmune diseases;
- assess the effectiveness of treatment.
It is important to remember: elevated CRP does not indicate a specific disease but rather signals the presence of inflammation in the body. Therefore, results are always interpreted by a doctor in conjunction with other tests (e.g., complete blood count, erythrocyte sedimentation rate (ESR), ferritin).
CRP: Normal Range
In healthy individuals, C-reactive protein (CRP) is present in minimal amounts (<5 mg/L). Elevated C-reactive protein levels usually indicate an acute inflammatory process. A physician should evaluate the test results in conjunction with clinical data, other laboratory test results, and the normal ranges (reference values) indicated on the test form.
Causes of Increased CRP Protein Concentrations
CRP levels can be used to determine the severity of inflammation. This requires further testing to determine the cause of the inflammation.
The main causes of elevated CRP are:
- bacterial infections (tonsillitis, pneumonia, pyelonephritis, sepsis) – often accompanied by high levels;
- viral infections (influenza, COVID-19, and other acute respiratory viral infections);
- chronic inflammatory diseases during exacerbations (arthritis, vasculitis, intestinal diseases);
- autoimmune diseases (when the immune system attacks the body's own tissues);
- tissue damage (injuries, burns, fractures);
- postoperative conditions and the recovery period;
- necrosis (tissue death, for example, in the presence of a myocardial infarction);
- oncological processes (CRP levels may increase with some tumors);
- metabolic conditions (obesity, diabetes – can maintain chronic low-level inflammation).
