How does normal erythrocyte sedimentation occur?
Under normal conditions, erythrocytes possess a negative surface charge. Because of this, cells with the same charge mutually repel each other and remain suspended in the plasma. The physical reason for their gradual sedimentation is that the relative density of erythrocytes is higher than that of the surrounding plasma.
What is the mechanism of increased ESR?
Acceleration of sedimentation is associated with changes in the physicochemical properties of blood, primarily the plasma protein spectrum and the ratio of plasma to formed elements.
- Decreased zeta potential — large molecular weight proteins (fibrinogen, immunoglobulins, C-reactive protein, ceruloplasmin, $\alpha$- and $\gamma$-globulins, and other acute-phase proteins) adsorb onto erythrocyte membranes. They decrease the negative charge of the cells, reducing mutual repulsion.
- Aggregation — decreased repulsion leads to the aggregation of erythrocytes into 'rouleaux' (stacks of coins).
- Increased effective density of aggregates — these aggregates are less stable in a gravitational field and settle faster.
Cations (hydrogen, potassium, calcium ions, etc.) also contribute to acceleration by neutralizing the negative charge of undamaged erythrocyte membranes, causing charge reversal to positive and the adhesion of oppositely charged cells. In immunopathological conditions and tumor growth, adhesive transmembrane glycoproteins may also be involved.
What conditions and substances increase ESR?
Elevated ESR is caused by an increased concentration of substances with pro-aggregant action: fibrinogen, globulins, C-reactive protein, ceruloplasmin, other acute-phase proteins; it is also associated with dysproteinemia, paraproteinemia, or alterations in acid-base balance.
- Inflammatory processes — bacterial infections, infectious and inflammatory diseases, inflammation of various etiologies, tuberculosis. An elevated ESR is noted in acute viral hepatitis as a marker of inflammation, alcoholic hepatitis, and ovarian tumor torsion. An increase in ESR is one of the CBC changes during a generalized reaction to a tuberculin skin test (Koch's test).
- Rheumatic and autoimmune diseases — accompanied by changes in plasma protein composition.
- Oncological diseases — neoplastic disorders, especially those accompanied by paraproteinemia; Hodgkin lymphoma, multiple myeloma, non-Hodgkin lymphomas with paraproteinemia.
- Anemia — a reduced red blood cell count leads to accelerated sedimentation.
- Alkalosis — shifting pH toward the alkaline side increases ESR.
- Endocrine and metabolic factors — diabetes mellitus, thyrotoxicosis, hypercholesterolemia.
- Physiological states and hormones — stress, pregnancy, and the influence of steroid hormones: glucocorticoids and estrogens.
- Kidney and liver pathologies.
Why might ESR be decreased?
A decreased ESR is associated with the following conditions:
- Erythrocytosis — an increased number of red blood cells, hemoconcentration.
- Acidosis — shifting pH toward the acidic side.