The ESR (Erythrocyte Sedimentation Rate) test measures how quickly red blood cells (erythrocytes) settle at the bottom of a test tube containing a blood sample over the course of one hour.
A faster-than-normal rate may indicate the presence of inflammation, infection, or certain diseases, such as rheumatoid arthritis, lupus, or cancer. However, it is a nonspecific test, meaning it does not pinpoint the exact cause of inflammation, but rather indicates that there may be an issue in the body. It is often used in conjunction with other tests to help diagnose and monitor inflammatory or autoimmune conditions.