C-reactive protein in the blood

Reference values (norm) for the concentration of C-reactive protein (CRP) in blood serum are less than 5 mg/l.

C-reactive protein (CRP) is a protein consisting of 5 identical, non-covalently linked ring subunits. C-reactive protein is determined in the blood serum during various inflammatory and necrotic processes and is an indicator of the acute phase of their course. It received its name due to the ability to precipitate the C-polysaccharide of the pneumococcal cell wall. Synthesis of C-reactive protein as an acute phase protein occurs in the liver under the influence of IL-6 and other cytokines.

C-reactive protein increases the mobility of leukocytes. By binding to T-lymphocytes, it affects their functional activity, initiating reactions of precipitation, agglutination, phagocytosis and complement fixation. In the presence of calcium, C-reactive protein binds ligands in the polysaccharides of microorganisms and causes their elimination.

The increase in the concentration of C-reactive protein in the blood begins within the first 4 hours from the moment of tissue damage, reaches a maximum after 24-72 hours and decreases during convalescence. An increase in the concentration of C-reactive protein is the earliest sign of infection, and effective therapy is manifested by its decrease. C-reactive protein reflects the intensity of the inflammatory process, and control over it is important for monitoring these diseases. The content of C-reactive protein during the inflammatory process can increase 20 times or more. The concentration of C-reactive protein in the blood serum above 80-100 mg / l indicates a bacterial infection or systemic vasculitis. With an active rheumatic process, an increase in C-reactive protein is found in most patients. In parallel with a decrease in the activity of the rheumatic process, the content of C-reactive protein also decreases. A positive reaction in the inactive phase can be due to a focal infection (chronic tonsillitis).

Rheumatoid arthritis is also accompanied by an increase in C-reactive protein (a marker of process activity), however, its determination cannot help in differential diagnostics between rheumatoid arthritis and rheumatic polyarthritis. The concentration of C-reactive protein is directly related to the activity of ankylosing spondylitis. In lupus erythematosus (especially in the absence of serositis), the concentration of C-reactive protein is usually not increased.

In myocardial infarction, CRP increases 18-36 hours after the onset of the disease, decreases by the 18-20th day, and returns to normal by the 30-40th day. High levels of C-reactive protein in myocardial infarction (as well as in acute cerebrovascular accident) are prognostically unfavorable signs. In angina, it remains within normal limits. C-reactive protein should be considered as an indicator of active atheromatosis and thrombotic complications in patients with unstable angina.

In edematous pancreatitis, the concentration of C-reactive protein is usually within the normal range, but it increases significantly in all forms of pancreatic necrosis. It has been established that C-reactive protein values above 150 mg/l indicate severe (pancreatic necrosis) or complicated acute pancreatitis. The study of C-reactive protein is important for determining the prognosis of acute pancreatitis. The predictive value of positive and negative results of C-reactive protein studies for determining an unfavorable prognosis of acute pancreatitis at a cutoff point of more than 100 mg/l is 73%.

After surgical interventions, the concentration of C-reactive protein increases in the early postoperative period, but begins to decrease rapidly in the absence of infectious complications.

Synthesis of C-reactive protein increases in tumors of various localizations. Increased concentration of C-reactive protein in the blood is observed in lung cancer, prostate cancer, stomach cancer, ovarian cancer and other tumors. Despite its non-specificity, CRP together with other tumor markers can serve as a test for assessing tumor progression and disease relapse.

There is a strong correlation between the degree of increase in C-reactive protein and ESR, but C-reactive protein appears and disappears before ESR changes.

An increase in the concentration of C-reactive protein is characteristic of rheumatism, acute bacterial, fungal, parasitic and viral infections, endocarditis, rheumatoid arthritis, tuberculosis, peritonitis, myocardial infarction, conditions after major operations, malignant neoplasms with metastases, multiple myeloma.

The C-reactive protein level does not increase significantly in viral and spirochetal infections. Therefore, in the absence of trauma, very high C-reactive protein values in most cases indicate the presence of a bacterial infection.

When interpreting the results of determining the concentration of C-reactive protein, it is necessary to take into account that viral infections, metastases of malignant tumors, sluggish chronic and a number of rheumatic diseases are characterized by an increase in the level of C-reactive protein to 10-30 mg / l. Bacterial infections, exacerbation of some rheumatic diseases (for example, rheumatoid arthritis) and tissue damage (surgery, myocardial infarction) are accompanied by an increase in the concentration of C-reactive protein to 40-100 mg / l (sometimes up to 200 mg / l), and severe generalized infections, burns, sepsis - up to 300 mg / l and more.

Determination of the C-reactive protein level in the blood serum can serve as one of the criteria for establishing indications and stopping antibiotic treatment. A C-reactive protein level below 10 mg/l indicates the absence of infection and there is no need for antibiotic treatment.

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