Erythrocyte sedimentation rate: why not determine it?
The clinical use of ESR to determine the inflammatory process caused by infection, inflammation or the development of a neoplasm is a non-specific method and its clinical significance should be reviewed.
Despite the fact that this article was published in 2001, the editors of the site found it possible to place it in the "News" section, as the determination of the erythrocyte sedimentation rate (ESR) has long been used to quantify the inflammatory process caused by infection, inflammation or the development of neoplasms, despite the fact that this method of diagnosis is not specific. The clinical use of this laboratory test is based on more than a century of experience. However, the results of the determination of the ESR can only be considered reliable if no other parameter, with the exception of the expected parameters, affects the indicator under study. Too many factors influence the test results and, therefore, its clinical significance needs to be reviewed.
The main influence on the rate of sedimentation of erythrocytes suspended in plasma is exerted by the degree of their aggregation. There are 3 main factors affecting the aggregation of red blood cells: surface cell energy, cell charge and the dielectric constant. The latter indicator is a plasma characteristic associated with the concentration of asymmetric molecules. An increase in the content of these proteins leads to an increase in the strength of the bonds between the red blood cells, leading to agglutination and coalescence (column formation) of the red blood cells and to a higher sedimentation rate.
A moderate increase in the concentration of plasma proteins of classes 1 and 2 can lead to an increase in ESR: extremely asymmetric proteins (fibrinogen) or moderately asymmetric proteins (immunoglobulins). Since fibrinogen is a marker for the acute phase, an increase in the level of this protein indicates the presence of infection, inflammation, or the appearance of tumor cells in the blood, leading to an increase in ESR in these processes. Despite the recognized non-specificity of the method for determining ESR, it is often overlooked that most other factors, in addition to the presence and severity of the inflammatory process, affect ESR , which questions the clinical significance of the test.
Unlike many factors influencing an indicator such as ESR, none of the known factors affect the level of C-reactive protein, with the exception of the presence and severity of infectious inflammation. The plasma half-life and the level of catabolism of C-reactive proteins are constant under almost all conditions. Therefore, the content of C-reactive protein in plasma is determined only by the level of its synthesis, which, in turn, depends only on the presence and severity of the infectious process. Reactive protein C belongs to group III of acute phase proteins, the content of which increases 100 to 1000 times during inflammation. Fibrinogen belongs to group II of proteins and its concentration increases from 2 to 4 times. These factors promote the determination of reactive protein C to assess the severity of the inflammatory response. The level of reactive protein C in the serum increases and also decreases faster than the level of fibrinogen in the serum, in this regard, the definition of reactive protein C as a marker of inflammation has chronological advantages.
Indeed, the determination of the ESR is faster and easier (it takes up to 1 hour to determine the ESR), to determine the level of C-reactive protein, it is necessary to carry out an ELISA or a study isotopic immunology. However, physicians who use the definition of ESR in practice rely more on the traditions of medicine than on the scientific rationale for the method and simple logic.