The erythrocyte sedimentation rate (ESR), or sedimentation rate (sed rate), is a measure of the settling of red blood cells in a tube of blood during one hour. The rate is an indication of inflammation and increases in many diseases.
ESR is increased in rheumatoid diseases, most infections, and in cancer. An advanced rate doesn't diagnose a specific disease, but it does indicate that an underlying disease may be present.
A physician can use ESR to monitor a person with an associated disease. When the disease worsens, the ESR increases; when the disease improves, the ESR decreases. The ESR doesn't always follow the course of cancer.
ESR is called an acute-phase reactant test, meaning that it reacts to acute conditions in the body, such as infection or trauma. The rate increase follows a rise in temperature and white blood cells count, peaks after several days, and usually lasts longer than the elevated temperature or white blood cells count.
The ESR should not be used to screen healthy persons for disease.
The ESR test is a simple test dating back to the ancient Greeks. A specific amount of diluted, unclotted blood is placed in a special narrow tube and left undisturbed for exactly one hour. The red cells settle towards the bottom of the tube, and the pale yellow liquid (plasma) rises to the top. After 60 minutes, measurements are taken of the distance the red cells traveled to settle at the bottom of the tube. Two methods, the Westergren and the Wintrobe, are used by laboratories; each method produces slightly different results. Most laboratories use the Westergren method.
Normally red cells don't settle far toward the bottom of the tube. Many diseases make extra or abnormal proteins that cause the red cells to move close together, stack up, and form a column (rouleaux). In a group, red cells are heavier and fall faster. The faster they fall, the further they settle, and the higher the ESR.
The ESR test is covered by insurance when medically necessary. Results are usually available the same or following day.
Nancy J. Nordenson, The Gale Group Inc., Gale, Detroit,