What factors influence the ESR?
Any condition that causes either a rise in the concentration of acute-phase reactants or hypergammaglobulinemia (polyclonal or monoclonal) will cause an elevation of the ESR. The increased concentration of these proteins decreases the negative charge of RBCs, dissipating inter-RBC repulsive forces and leading to closer aggregation (rouleaux formation). This causes the RBCs to fall faster resulting in an elevation of the ESR. Noninflammatory conditions that can elevate the ESR (typically through an increase in plasma fibrinogen) include pregnancy, diabetes, end-stage renal disease, and heart disease. In addition, aging, anemia, female sex, and obesity can be associated with an elevated ESR. Alterations in number (polycythemia), size (microcytosis), or shape (spherocytosis, sickle cell) of erythrocytes may physically interfere with rouleaux formation and thus lower the ESR.
Pearl : A rough rule of thumb for the age-adjusted upper limit of normal for ESR (mm/hour) is: Male = age/2 Female = (age + 10)/2
