Erythrocyte Sedimentation Rate

Overview

• The rate at which RBCs fall in a test tube forming a measurable clear supernatant
• ↑ ESR caused by
  • infections
  • inflammation
    • inflammation results in increased acute phase reactants (e.g. fibrinogen) which results in RBC agglutination
    • agglutination causes RBCs to fall at a faster rate within the test tube 
    • e.g. temporal arteritis and SLE
  • cancer
  • pregnancy
    • greater plasma volume results in easier formation of a clear supernatant due to decrease in density of plasma relative to density of a single RBC
    • increase in acute phase proteins (e.g. fibrinogen) promotes RBC aggregation
• ↓ ESR caused by
  • sickle cell
    • changes in RBC morphology result in altered sedimentation
  • polycythemia 
    • more RBCs take longer to create a supernatant
  • CHF