Abstract

The erythrocyte sedimentation rate (ESR) has become a ubiquitously used technique in medicine as a marker of systemic illness. The test involves placing anticoagulated whole blood into an upright test tube and monitoring the rate at which red blood cells (RBC) fall over time. Negative charges keep RBC from sticking together. If this charge is neutralised, RBC stack into chains, or rouleaux, and fall more rapidly. ESR can be measured with a variety of tests: Westergren and modified Westergren; Wintrobe; micro-ESR. The Westergren is the most commonly used method of performing the ESR. Technical factors, such as temperature, time from specimen collection, tube orientation and vibration, can affect the results. RBC size, shape and concentration impact the ESR. Plasma characteristics are also important determinants of the ESR. Other factors that can change ESR include age, sex, race, medications and disease states, such as obesity, hypofibrinogenaemia and congestive heart failure. Other acute-phase reactants besides the ESR include C-reactive protein, fibrinogen, complement, ferritin, plasma viscosity, serum amyloid A and albumin. When clinical suspicion for infection or inflammation is low, a normal ESR can reassure that there is no active disease. The slow rise (48 h) and fall of the ESR relative to other acute-phase reactants may make it superior for monitoring inflammation in more chronic conditions. In conjunction with physical findings and other laboratory values, the ESR value can be used to screen for disease or disease complications, aid in disease diagnosis or assess disease activity or response to therapy.