Sedimentation occurs when erythrocytes or red blood cells (RBCs) clump or aggregate together in a column-like manner (rouleaux formation). These changes are related to alterations in the plasma proteins. Normally, erythrocytes settle slowly because normal RBCs do not form rouleaux.
The erythrocyte sedimentation rate (ESR) is the rate at which erythrocytes settle out of anticoagulated blood in 1 hour. This test is based on the fact that inflammatory and necrotic processes cause an alteration in plasma proteins, resulting in RBC aggregation, which makes them heavier and more likely to fall rapidly when placed in a special vertical test tube—the faster the cells settle, the higher the ESR. The ESR should not be used to screen asymptomatic patients for disease. It is most useful for diagnosis of temporal arteritis, rheumatoid arthritis, and polymyalgia rheumatica. The ESR is not diagnostic of any disease but rather is an indication that a disease process is ongoing and must be investigated. It is also useful in monitoring the progression of inflammatory diseases; if the patient is being treated with steroids, the ESR will decrease with clinical improvement.
Normal findings (by Westergren's Method)
Men: 0 to 15 mm/hr (over age 50: 0 to 20 mm/hr)
Women: 0 to 20 mm/hr (over age 50: 0 to 30 mm/hr)
Increased ESR is found in:
- collagen diseases, systemic lupus erythematosus
- inflammatory diseases
- carcinoma, lymphoma, neoplasms
- acute heavy metal poisoning
- cell or tissue destruction, myocardial infarction
- toxemia, pregnancy (third month to 3 weeks postpartum)
- Waldenström macroglobulinemia, increased serum immunoglobulins
- nephritis, nephrosis
- infective endocarditis
- rheumatoid arthritis, gout, arthritis, polymyalgia rheumatica
- hypothyroidism and hyperthyroidism.
Decreased ESR—A number of factors may spuriously result in a very low ESR or ESR that is less than the expected level in a patient with acute or chronic inflammation. These include:1
- abnormalities of erythrocytes—changes in red cell shape or number may reduce the ESR, including sickle cell disease, anisocytosis, spherocytosis, and acanthocytosis, as well as microcytosis and polycythemia
- extreme leukocytosis
- extremely high serum bile salt levels
- heart failure
- technical factors, including:
- clotting of the blood sample or delay in testing of greater than 2 hours
- low room temperature
- short ESR tube.
Extreme elevation of the ESR is found with infection, malignancy, and renal disease.