A common test called the erythrocyte sedimentation rate, or ESR, measures the rate of red cell precipitation in a sample of blood. Red cell precipitation is the settling of red cells to the bottom of a column of blood when left undisturbed. The test results are nonspecific, simply indicating the presence or absence of an abnormality without pointing to any particular diagnosis. A wide variety of diseases and conditions can lead to increased rates of red cell sedimentation.
Test Procedure
The standard method of performing an erythrocyte sedimentation rate involves placing a sample of unclotted blood in a vertical glass column. The distance the red cell component settles after 60 minutes is measured in millimeters, and this number represents the ESR result. The rate of sedimentation is influenced by the concentrations and types of protein in the plasma surrounding the red cells, as well as red cell size and number. Normal values for individuals under age 50 are less than 15 mm/hour in men and less than 20 mm/hour in women, as reported by MedlinePlus.
Increases in ESR Without Disease
Not all elevations of ESR indicate the presence of disease. Normal pregnancy causes increased levels of fibrinogen, a blood protein, resulting in a moderately elevated ESR. Slightly increased values may also be seen in females, with increasing age and certain medications such as oral contraceptives and vitamin A, according to Lab Tests Online.
Increases in ESR With Disease
The ESR may be increased by any inflammatory disorder, tissue damage or abnormal blood protein level. These include disorders such as infection, anemia, collagen vascular or autoimmune disease, malignancy, kidney or thyroid disease.
The test does not differentiate between these causes, which explains why it is not helpful in determining a specific diagnosis. ESR levels fluctuate with disease activity, and because of the simplicity and low cost of the test may be useful in monitoring the progression of a known disease, according to "Clinical Diagnosis and Management by Laboratory Methods."
Markedly Elevated ESR
Very high ESR levels, greater than 100 mm/hour, nearly always indicate significant disease, as discussed by Dr. Malcolm Brigden in the October 1, 1999 issue of "American Family Physician." Multiple myeloma, temporal arteritis, polymyalgia rheumatica, metastatic malignancy and widespread serious infections are the most common causes of such high levels. Evidence of these diseases is usually already obvious by physical examination or other signs and symptoms.
Interpretation
An elevated ESR is a nonspecific marker for inflammation as well as a wide variety of other conditions. A mildly elevated ESR without other signs or symptoms may not require any additional evaluation. In most cases, a health care practitioner will need to consider an individual's medical history and physical examination, and order additional tests or studies to reach a specific diagnosis.
References
- MedlinePlus: ESR
- Lab Tests Online: ESR
- "Clinical Diagnosis and Management by Laboratory Methods"; John Bernard Henry M.D., (ed.); 1996
- "American Family Physician"; Clinical Utility of the Erythrocyte Sedimentation Rate; Malcolm L. Brigden M.D.; October 1, 1999
