The Erythrocyte Sedimentation Rate (ESR) test indirectly measures the degree of inflammation present in the body.
When blood cells face inflammation, they start clumping. These clumps sink inside a tube where the blood sample is placed. The rate at which these blood clumps sink, indirectly indicates the level of inflammation present in your body.
ESR test is not a diagnostic tool of a specific disease. Rather, it is used to monitor the course or response to treatment of certain diseases. Extremely high levels are found in cases of malignancy, hematologic diseases, collagen disorders and renal diseases.