ERYTHROCYTE SEDIMENTATION RATE (ESR)
Sed rate, or erythrocyte sedimentation rate (ESR), is a blood test that can reveal inflammatory activity in your body. A sed rate test isn’t a stand-alone diagnostic tool, but it may help your doctor diagnose or monitor the progress of an inflammatory disease.
When your blood is placed in a tall, thin tube, red blood cells (erythrocytes) gradually settle to the bottom. Inflammation can cause the cells to clump together. Because these clumps of cells are denser than individual cells, they settle to the bottom more quickly.
The sed rate test measures the distance red blood cells fall in a test tube in one hour. The farther the red blood cells have descended, the greater the inflammatory response of your immune system.
WHAT IS AN ESR TEST?
An erythrocyte sedimentation rate (ESR) test is sometimes called a sedimentation rate test or sed rate test. This test doesn’t diagnose one specific condition. Instead, it helps your doctor determine whether you’re experiencing inflammation. The doctor will look at ESR results along with other information or test results to help figure out a diagnosis. The tests ordered will depend on your symptoms. This test can also monitor inflammatory diseases.
In this test, a tall, thin tube holds a sample of your blood. The speed at which the red blood cells fall to the bottom of the tube is measured. Inflammation can cause abnormal proteins to appear in your blood. These proteins cause your red blood cells to clump together. This makes them fall more quickly.
RISKS OF THE ESR TEST
HAVING YOUR BLOOD DRAWN INVOLVES HAS MINIMAL RISKS. POSSIBLE COMPLICATIONS INCLUDE:
- excessive bleeding
- hematoma, or bruising
- inflammation of the vein
You will probably feel mild to moderate pain when the needle pricks your skin. You might also feel throbbing at the puncture site after the test.
NORMAL ESR TEST RESULTS
ESR test results are measured in mm/hr, or millimeters per hour.
THE FOLLOWING ARE CONSIDERED NORMAL ESR TEST RESULTS:
- Women under age 50 should have an ESR under 20 mm/hr.
- Men under age 50 should have an ESR under 15 mm/hr.
- Women over age 50 should have an ESR under 30 mm/hr.
- Men over age 50 should have an ESR under 20 mm/hr.
- Newborns should have an ESR under 2 mm/hr.
- Children who haven’t reached puberty yet should have an ESR between 3 and 13 mm/hr.
WHY IT’S DONE?
Sed rate tests were used more frequently in the past than they are today because more-specific measures of inflammatory activity are now available. Today, the test is most often used if your doctor suspects you have:
- Giant cell arteritis
- Polymyalgia rheumatica
- Rheumatoid arthritis
A sed rate test can also help determine the severity of your inflammatory response and monitor the effect of treatment.
Because a sed rate test can’t pinpoint the problem that’s causing inflammation in your body, it’s usually accompanied by other blood tests, such as the C-reactive protein (CRP) test.