The ESR test measures the erythrocyte sedimentation rate, which is how quickly red blood cells settle at the bottom of a blood sample. Doctors cannot use the results of the test to diagnose a specific disease because many different health conditions can cause the ESR to be high or low.
Doctors call the ESR test a nonspecific test, as it only confirms the presence or absence of inflammatory activity in the body. Doctors typically use other lab tests, clinical findings, and the person's health history alongside ESR test results to make a diagnosis.
Doctors also use the ESR test to monitor how conditions, such as those below, are progressing or responding to treatment.
- rheumatoid arthritis, an autoimmune condition that causes inflammation in the joints
- temporal arteritis, a type of blood vessel inflammation
- polymyalgia rheumatica, a complication of temporal arteritis
- systemic vasculitis, inflammation of the lining of the blood vessels
In this article, we look at the ESR test procedure and what the results might indicate. We also explain the possible risks of the procedure.
The ESR test measures the rate at which the red blood cells, or erythrocytes, in a sample of blood settle at the bottom. This process of settling is called sedimentation.
A doctor will draw a small amount of blood from the individual's vein and send it to a laboratory. There, lab technicians will transfer the blood to a vertical test tube in which the red blood cells will slowly settle at the bottom. This will leave a clear, yellowish fluid at the top, which is blood plasma.
The result of the test will depend on the amount of plasma at the top of the tube after 1 hour. The measurement will be in millimeters per hour (mm/hr).
Red blood cells settle at a faster rate in people with inflammatory conditions. These conditions trigger an inflammatory process in the body, which leads to an increase in the number of proteins in the blood. This increase causes red blood cells to clump together and settle more quickly.
People whose red blood cells settle faster will have elevated ESR values, indicating to doctors that a medical condition may be present.
The result of the ESR test is the amount of plasma remaining at the top of the test tube after 1 hour.
The test is not specific to a particular condition, which means that doctors have to use the results alongside other clinical information to make an accurate diagnosis and determine whether or not the individual has a disease.
The normal reference range for ESR results is 1–13 mm/hr for males and 1–20 mm/hr for females. These values can also vary depending on the person's age. People with ESR results outside the standard range may have a medical condition.
People with low ESR values may have:
- sickle cell anemia, a condition that affects the shape of red blood cells
- leukemia, a blood cell cancer
- a high red blood cell count
- congestive heart failure
- low levels of the protein fibrinogen in the blood
- hyperviscosity, an increase in blood thickness
- a very high white blood cell count
Moderately elevated results
A moderately elevated ESR may not always indicate a health condition.
However, it is possible that people whose ESR value is slightly high may have one of the following conditions:
- rheumatoid arthritis
- anemia, a reduced number of red blood cells
- thyroid disease
- kidney disease
- red blood cell abnormalities, such as macrocytosis
- some forms of cancer, such as lymphoma
- tuberculosis, a type of lung infection
- a bone infection
- a heart infection
- a systemic infection
Extremely elevated results
An extremely high ESR value, which is one above 100 mm/hr, may indicate one of these conditions:
- multiple myeloma, a cancer of plasma cells
- Waldenstrom's macroglobulinemia, a white blood cell cancer
- temporal arteritis or polymyalgia rheumatica
- hypersensitivity vasculitis, a reaction to an allergen that results in blood vessel inflammation
Doctors will typically compare the ESR test result with other test results to confirm a suspected diagnosis. They will also consider the symptoms and signs that a person is experiencing and their personal and family medical history.
The ESR test is simple and quick, taking just a few minutes to complete. The procedure is very safe and poses few risks.
People who take the test may feel a slight sting when the needle pricks the arm. Some people may bleed slightly where the needle pierces the skin, and others may feel temporarily faint or dizzy.
After the test, people may get a small bruise at the puncture site or experience mild soreness in the arm, which can last for a few days. In more sensitive people, this bruising may turn into a hematoma.
People with abnormal ESR values may not always have a medical condition that requires treatment. Slightly higher levels can also occur due to pregnancy, menstruation, or advancing age.
In cases where a non-medical cause or underlying medical condition may be affecting the test result, doctors usually order a second ESR test and other types of test to help make a diagnosis.
If the doctor concludes that someone does have a medical condition, they are likely to prescribe a treatment specific to the condition. Treatment may involve:
- antibiotics, where there is an infection
- nonsteroidal anti-inflammatory drugs (NSAIDs), such as naproxen, diclofenac, and celecoxib
- corticosteroid medications, such as methylprednisolone and dexamethasone
NSAIDs and corticosteroids are medications that treat inflammation.
An ESR test result outside of the normal range is not necessarily a cause for concern. There are some non-medical causes of abnormal results.
Although doctors cannot diagnose a specific medical condition with an ESR test, the result can establish whether or not there is inflammation in the body.
If the test indicates that there may be an issue, doctors will need to order further tests and get additional clinical information to make an accurate diagnosis.