An erythrocyte sedimentation rate (ESR) test does not diagnose one specific condition. Instead, it helps your doctor determine whether you are experiencing inflammation. The doctor will look at ESR results along with other information or test results to help figure out a diagnosis.
Which tests are ordered will depend on your symptoms. This test can also be used to monitor inflammatory diseases.
Erythrocyte sedimentation rate, C-reactive protein and plasma viscosity are blood tests that detect inflammation. These are useful tests to help diagnose and monitor the activity of certain diseases.
In this test, a sample of your blood is placed in a tall, thin tube. 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.
This test is sometimes called a sed (or sedimentation) rate test.
Inflammation and blood proteins
If you have inflammation in a part of your body then extra protein is often released from the site of inflammation and circulates in the bloodstream.
The erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and plasma viscosity (PV) blood tests are commonly used to detect this increase in protein, and so are markers of inflammation.
Why Doctors Perform an ESR Test
Your doctor may order an ESR test to help detect inflammation in your body. This can be useful in diagnosing conditions that cause inflammation, such as autoimmune diseases, cancers, and infections.
An ESR test can be used to monitor inflammatory conditions, such as rheumatoid arthritis or systemic lupus erythematosus. Your doctor might also order this test if you are experiencing some types of arthritis, fevers, and muscle problems.
The ESR test is rarely performed alone. Instead, it will be combined with other tests to determine the cause of your symptoms.
What conditions affect the erythrocyte sedimentation rate and C-reactive protein level?
Raised ESR, CRP and PV levels are all markers of inflammation. Generally, PV and ESR do not change as rapidly as CRP does, either at the start of inflammation or as it goes away.
CRP is not affected by as many other factors as the PV or ESR, making it a better marker of some types of inflammation.
PV, however, is more sensitive and more specific than either ESR or CRP when monitoring the activity of rheumatoid arthritis.
ESR, CRP and PV can be raised in many inflammatory conditions – for example:
- Certain infections (mainly bacterial infections).
- Certain types of arthritis.
- Various other muscular and connective tissue disorders – for example, polymyalgia rheumatica or temporal arteritis.
- Tissue injury and burns.
- Crohn’s disease.
- Rejection of an organ transplant.
- Heart attack.
- Some conditions lower the ESR – for example, heart failure, polycythaemia, sickle-cell anaemia, and cryoglobulinaemia.
When are these tests used?
To help diagnose diseases
ESR, CRP and PV are nonspecific tests. Basically, a raised level means that “something is going on”, but further tests will be needed to clarify the cause of the illness.
For example, you may be unwell but the cause may not be clear. A raised ESR, CRP and PV may indicate that some inflammatory condition is likely to be the cause. This may prompt a doctor to do further tests to find the cause.
It is not usually possible to make a diagnosis of a certain condition just from a raised ESR, CRP or PV level.
However, before you have further tests, your doctor may suggest that you have the ESR, CRP or PV test repeated after a period of several weeks or months.
If it has been raised by a recent infection (a very common cause) then it is likely to return to normal when your infection improves and you will not then need any further tests.
Preparing for the ESR Test
Many different medications and drugs can affect your ESR levels. These include:
- aspirin (in high doses)
- salicylate (in high doses)
Tell your doctor if you are taking any medications. You will be told whether you should temporarily stop taking them before the test.
The ESR Test
All this test involves is a blood draw. The skin directly over a vein will be cleaned, and a needle will be inserted to collect your blood.
After the blood has been collected, the needle will be removed, and the site of the puncture will be covered to stop any bleeding. It should take only a minute or two.
Risks of the ESR Test
Having your blood drawn involves only minimal risks. Possible complications include:
- excessive bleeding
- hematoma (bruising)
- inflammation of the vein
- You will probably feel mild to moderate pain when the needle is inserted. You might also feel throbbing after the needle has been removed.
Normal ESR Test Results
ESR test results are measured in mm/hr, or millimeters per hour.
Normal results are generally:
- women under 50: under 20 mm/hr
- men under 50: under 15 mm/hr
- women over 50: under 30 mm/hr
- men over 50: under 20 mm/hr
- newborns: under 2 mm/hr
- children before puberty: 3 to 13 mm/hr