An elevated erythrocyte sedimentation rate (ESR) refers to the fact that the erythrocytes, or red blood cells, fall more quickly when blood is placed in a test tube. The ESR is a blood or hematology test which measures the rate at which red blood cells fall to the bottom of a test tube in a one hour time period. A higher than normal erythrocyte sedimentation rate may indicate the presence of inflammation in the body and the test is performed, in combination with other diagnostic tests, to detect some inflammatory conditions, such as arthritis.
Blood is composed of plasma and various various blood cells — erythrocytes or red blood cells, leukocytes or white blood cells and thrombocytes or platelets, each which perform vital roles in the functioning of the body. The red blood cells are relatively heavy so that, when a sample of blood is placed in a test tube, they tend to sink slowly to the bottom. In the case of an elevated erythrocyte sedimentation rate, this sedimentation rate is quicker than what is expected.
The reason for an elevated erythrocyte sedimentation rate is that, when there is inflammation, the body produces specific proteins which cause the red blood cells, erythrocytes, to clump together, making them heavier and causing them to drop down to the bottom of the test tube more quickly. There is no preparation necessary when the doctor orders an ESR to be done and it is a simple blood test. Due to its non-specificity, other tests are normally also necessary for a definitive diagnosis.
While an elevated erythrocyte sedimentation rate doesn't necessarily have effects itself, it may indicate an underlying disorder such as polymyalgia rheumatica, temporal arteritis or multiple myeloma. The ESR may also be used to monitor the response of some of these inflammatory conditions to treatment, so it may be repeated regularly during such treatment. The measurement is done in millimeters per hour (mm/hr) and is expected to be slightly different in men and women.
A number of other factors may affect the ESR, all of which will be taken into consideration by the hematologist and diagnosing doctor. These include pregnancy, anemia, age, the use of some medications and infection. It is for this reason, too, that the ESR is not considered a diagnostic test on its own and diagnosis is made using the ESR in combination with complete examination and other diagnostic tests. These may include a full blood count and a measurement of C-reactive protein, which is another indicator of inflammation.