Definition of ESR:

ESR stands for erythrocyte sedimentation rate. It is commonly called a "sed rate."

It is a test that indirectly measures how much inflammation is in the body.

How the test is performed:

A blood sample is needed. For information on how this is done, see: Venipuncture

The blood sample is sent to a lab. The test measures how fast red blood cells called erythrocytes fall to the bottom of a tall, thin tube.

How to prepare for the test:

There are no special preparations needed.

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

A "sed rate" is often ordered for someone who is having unexplained fevers, certain types of arthritis, muscle symptoms, or other vague symptoms that cannot be explained.

Once a diagnosis has been made, this test may be used to monitor whether the illness is becoming more active or flaring up.

This test can be used to monitor inflammatory diseases or cancer. It is a screening test, which means it cannot be used to diagnose a specific disorder.

However, it is useful for detecting and monitoring:

• Autoimmune disorders
• Certain forms of arthritis
• Inflammatory diseases that cause vague symptoms
• Tissue death
• Tuberculosis