Erythrocyte sedimentation rate

Erythrocyte Sedimentation Rate (ESR) is a commonly performed laboratory test that can provide indirect evidence of inflammation in the body. While not definitive for any particular condition, an elevated ESR can signal underlying issues that may require further investigation.

Erythrocyte sedimentation rate (ESR)

Overview

The Erythrocyte Sedimentation Rate (ESR) test measures the rate at which red blood cells (erythrocytes) settle at the bottom of a vertical tube over a period of one hour. The result is typically expressed in millimeters per hour (mm/hr). A faster-than-normal rate may indicate inflammation in the body.

Indications and Limitations

The ESR test is nonspecific, meaning it doesn't pinpoint the cause of inflammation or confirm a particular diagnosis. Instead, it serves as a general marker of underlying disease, particularly when combined with other medical information. ESR is often used in diagnosing conditions like rheumatoid arthritis, temporal arteritis, and systemic lupus erythematosus, and it can also be used to monitor disease activity and response to therapy in these conditions.

However, several factors such as age, pregnancy, anemia, and kidney disease can affect ESR levels, making it an imperfect measure.

Procedure

Blood is typically collected from a vein in the arm using standard blood-draw procedures. The blood is then transferred into a vertical tube and left undisturbed for an hour. The distance that the red blood cells fall (sediment) from the top of the tube after one hour is measured and recorded as the ESR.

Interpretation

Normal values for ESR vary by age and sex. For men, a normal ESR is usually less than 22 mm/hr, while for women it's less than 29 mm/hr. Elevated levels can indicate the presence of an inflammatory process in the body, while lower levels, though less common, can occur in conditions like polycythemia, extreme leukocytosis, and protein abnormalities.