Erythrocyte Sedimentation Rate (ESR)

The Erythrocyte Sedimentation Rate (ESR) is a blood test that measures how quickly erythrocytes (red blood cells) settle at the bottom of a test tube containing a blood sample. It indirectly measures how much inflammation is in the body.

Procedure

The procedure for an ESR test involves the following steps:

• A blood sample is drawn from a vein, usually from the arm.
• The blood sample is placed in a test tube containing an anticoagulant to prevent clotting.
• The test tube is left to stand upright for a specified period, usually one hour.
• The distance the red blood cells have fallen (settled) from the top of the blood column is measured and recorded in millimeters per hour (mm/h).

Principle

The principle behind the ESR test is based on the fact that inflammatory states lead to the production of acute-phase proteins, which cause red blood cells to aggregate and settle more quickly. The higher the level of inflammation, the faster the red blood cells will settle.

Reference Values

Reference values for ESR can vary slightly between laboratories but are generally considered to be:

• 0-20 mm/h for adults
• 0-15 mm/h for children
• 0-30 mm/h for newborns

Clinical Significance

The ESR test is used to detect inflammation in the body, which can be caused by a variety of conditions, including:

• Infections (e.g., bacterial, viral, fungal)
• Autoimmune disorders (e.g., rheumatoid arthritis, lupus)
• Cancer
• Tissue damage or injury

Limitations

The ESR test has several limitations:

• It is a non-specific test, meaning that an elevated result does not indicate a specific diagnosis.
• Results can be influenced by various factors, such as age, sex, and the presence of certain medical conditions (e.g., anemia, pregnancy).

Interpretation

Interpretation of ESR results should be done in conjunction with other laboratory tests, medical history, and physical examination. An elevated ESR result may indicate the need for further testing to determine the underlying cause of inflammation.