Inflammation markers are proteins whose concentration in the blood depends on disease processes in our body. Testing the level of these substances is used in diagnostics. These tests are helpful in detecting and classifying bacterial, viral and fungal infections. They are also used in monitoring the course of rheumatic diseases and some cancers. The most common indicator of inflammation in the body is CRP.

Inflammation markersare chemical compounds classified as acute phase proteins. Physiologically, their task is to control the processes aimed at eliminating the intruder, which is a virus, fungus or bacteria. Their plasma concentration increases or decreases in response to inflammation. The group of markers includes proteins of diagnostic importance, such as: CRP, IL-6, TNF-α and PC.

What are acute phase proteins?

Acute phase proteins are substances that trigger specific reactions in the body, such as fever and activation of leukocytes and neutrophils.

In response to tissue damage, inflammatory cells release cytokines into the bloodstream. The most notable of these are the interleukins IL1, IL6 and TNFα. In response to the increase in these substances, the liver starts synthesizing some important acute phase proteins such as CRP.

Substances that rise during infection are referred to as "positive" proteins. At the same time, the production of many other immune proteins, which are called "negative" acute-phase reagents, decreases.

Markers most often used in diagnostics

The most important marker of inflammation is the C-reactive protein, abbreviated as CRP. This protein is produced in elevated amounts by the liver in response to infections and damage to the body's tissues. Inflammatory cytokines are the impulse leading to the increase of CRP concentration in the blood.

In addition to the C-reactive protein, PCT, i.e. procalcitonin, is also a marker of inflammation used in diagnostics.

CRP functions in the body

CRP attaches to compounds found on the surface of dead or damaged cells and some bacteria. It then targets those macrophage units that flush them outby phagocytosis. Thanks to this mechanism, C-reactive proteins are an important link in the body's immune processes.

In simpler words, CRP molecules are markers that find cells that need to be removed from the body, and then attach to their surface. Macrophages recognize marked objects and then "eat" them. Interestingly, eating cells have the ability to stimulate the liver to produce C-reactive proteins. This is due to the production of interleukin 6 by them. This substance is the most important inflammatory cytokine stimulating the synthesis of CRP.

Regulation of CRP concentration in the body

Macrophages produce interleukin 6 in response to viral, bacterial or fungal infections as well as tissue damage and necrosis. These conditions, through the action of this cytokine, ultimately stimulate the synthesis of CRP and fibrinogen in the liver.

The opposite is true for interferon alpha produced as a consequence of viral invasion. It inhibits the production of CRP. For this reason, the concentration of C-reactive proteins during viral infections is lower than in bacterial ones.

Use of CRP in diagnostics

Determining the concentration of CRP in a patient is useful in diagnosing disease development or treatment efficacy. It is primarily about serious chronic diseases such as cancer and rheumatoid arthritis. There is also a modern method that allows the assessment of cardiovascular risk based on the level of C-reactive proteins in the patient.

It turns out, however, that the CRP test can also be used in the rationalization of antibiotic therapy. A simple test can distinguish a bacterial from a viral infection. High levels of an inflammatory marker indicate bacteria. In this case, the use of an antibiotic is recommended. If the result is low, this type of therapy will only weaken the body. Such a test can be performed in a diagnostic laboratory. There are also kits that allow you to do it yourself at home.

The concentration of CRP protein in a he althy organism is in the range of 0-8 mg / L. In the case of bacterial infections, the level of this protein can be up to 1000 times above the norm. The maximum concentration is observed within 24-48 hours of the onset of the attack by the pathogen.

The CRP test is used in diagnostics for:

  • cardiovascular disease risk assessment
  • risk assessment of coronary heart disease
  • detection of chronic inflammation
  • risk assessment of certain types of cancer
  • treatment path for rheumatoid arthritis

CRP level and disease riskneoplastic

The role of chronic inflammation as a factor in the formation of neoplastic changes in the body is not yet well understood. Some organs of the body show greater sensitivity to this factor. There is a relationship between increased levels of C-reactive protein and the risk of developing certain types of cancer.

A 2004 study showed that there is a relationship between colorectal cancer incidence and the patient's CRP level. Sick people had a higher mean concentration of this protein in the blood than he althy people. These results suggest that low levels of inflammatory mediators are associated with a lower risk of colon cancer. This indicates the prophylactic potential of the use of anti-inflammatory drugs in people with diagnosed chronic inflammation in the intestine.

Role of precalcitonin (PCT) as a marker of inflammation

Procalcitonin (PCT) is a peptide precursor of the hormone calcitonin, which is involved in maintaining the calcium balance in the body. The level of PCT in the blood of he althy people is below the detection limit in commonly used laboratory tests.

The level of procalcitonin increases in response to a pro-inflammatory stimulus. The strongest impulse causing the increase in the concentration of this substance in the body is a bacterial infection. For this reason, PCT is classified as an acute phase protein.

Due to the rapid increase in the concentration of this marker during a bacterial infection, the examination of its level is used to detect this type of infection. This test can also help you decide whether to start taking an antibiotic.

PCT is a marker that is effective in distinguishing between viral and bacterial infections. This is due to the fact that the release of this substance into the blood is attenuated by IFN-γ, which is released in response to contact with the virus. Therefore, the concentration of procalcitonin during viral infection is low.

The PCT concentration test in the blood is a test that allows you to quickly detect sepsis in a patient. This allows for a quick and effective method of life-saving therapy. Subsequent monitoring of the patient's procalcitonin level is a good method of assessing whether the administered antibiotic is working. A decrease in PCT concentration by 30-50% daily indicates an improvement in the patient's condition.

PCT level testing is used for:

  • recognition of a bacterial infection,
  • sepsis detection and immediate treatment,
  • to assess the severity of sepsis, systemic inflammatory reaction, shock and organ failure,
  • make an individualized decision about antibiotic treatment,
  • decision to end antibiotic therapy

The advantage of PCT testing is the rationalization of treatment, allowing you to minimize costs. This is especially important in intensive care units.

Differences between PCT and CRP testing

The CRP level is a test that is performed routinely. It is very sensitive, but its specificity is low. In this case, one result may indicate many diseases.

PCT has an extremely fast reaction time compared to other inflammatory markers. It is particularly important in assessing the patient's condition in critical cases. I am talking here primarily about sepsis.

About the authorSara Janowska, MA in pharmacyPhD student of interdisciplinary doctoral studies in the field of pharmaceutical and biomedical sciences at the Medical University of Lublin and the Institute of Biotechnology in Białystok. A graduate of pharmaceutical studies at the Medical University of Lublin with a specialization in Plant Medicine. She obtained a master's degree defending a thesis in the field of pharmaceutical botany on the antioxidant properties of extracts obtained from twenty species of mosses. Currently, in his research work, he deals with the synthesis of new anti-cancer substances and the study of their properties on cancer cell lines. For two years she worked as a master of pharmacy in an open pharmacy.

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