What Is a Erythrocyte Sedimentation Rate Blood Test?

The erythrocyte sedimentation rate blood test is a commonly performed hematology test that is mainly used to assess for the presence of inflammation in the body. Results of the test are often referred to as the erythrocyte sedimentation rates (ESR), or as simply the sedimentation rates. Although the results obtained from the test are often nonspecific, they can help point doctors or other health care providers towards a correct diagnosis, especially if they interpret the results in the context of other symptoms and laboratory findings.

In order to perform the erythrocyte sedimentation rate blood test, a sample of a patient's blood is taken. As soon as possible after the blood is collected, a sample of the blood is put in a special tube and allowed to rest. The red blood cells, or erythrocytes, are denser than the other components of the blood and tend to settle to the bottom of the tube over time. A sedimentation rate represents how fast the red blood cells fall. This test was conceived and test by a Polish physician name Edmund Biernacki, so it is also referred to as the Biernacki reaction.

Measuring how fast the red blood cells settle to the bottom of a test tube offers important information about processes going on in the body. Conditions in which there is a lot of inflammation present in the body results in a buildup of proteins and other molecules on the surface of red blood cells. As a result, the erythrocytes clump together and acquire a higher effective density, increasing the speed at which they sink out of solution. In a completely healthy person, the erythrocyte sedimentation rate blood test should give results of 1-2 millimeters/hour.

Getting a high ESR value in a patient suggests the presence of inflammation, infection, autoimmune disease, or hematologic malignancies. Although laboratories can vary in what they consider a high ESR to be, typically a value greater than 10 millimeters/hour in men or 15 millimeters/hour in women is considered abnormal. Specific conditions known to have a strong association with an elevated ESR include temporal arteritis, endocarditis, malignant melanoma, anemia, and pelvic inflammatory disease.

Having a decreased erythrocyte sedimentation rate blood test can also suggest the presence of certain diseases. This finding is most commonly associated with diseases that cause the red blood cells to have structural abnormalities. Patients with sickle cell anemia, for example, have abnormal hemoglobin that can result in red blood cells acquiring a sickled shape. These patients tend to have a decreased ESR. Other conditions, including spherocytosis, microcytosis, and congestive heart failure, are also associated with low sedimentation rates.