Erythrocyte Sedimentation Rate (ESR) test is a non-specific laboratory test that measures the rate at which red blood cells (erythrocytes) settle in a vertical column of anticoagulated blood over a given period of time. The test is conducted by measuring the distance in millimeters between the top of the column of red cells and the top of the plasma after one hour. The ESR test is used to determine the degree of inflammation or infection present in the body, as the rate of sedimentation is known to increase in the presence of these conditions. The test can also help to monitor the progression of inflammatory diseases and the effectiveness of treatment over time. ESR is typically performed on WB-EDTA blood, and is a simple and low-cost test that does not require any special preparation from the patient. However, the results must be interpreted in conjunction with other clinical findings, as a high ESR does not necessarily indicate the presence of a specific disease or condition.