Erythrocyte sedimentation rate

The erythrocyte sedimentation rate (ESR), also called a sedimentation rate or Biernacki Reaction, is the rate at which red blood cells sediment in a period of 1 hour. It is a common hematology test that is a non-specific measure of inflammation. To perform the test, anticoagulated blood is placed in an upright tube, known as a Westergren tube, and the rate at which the red blood cells fall is measured and reported in mm/h.

Since the introduction of automated analyzers into the clinical laboratory, the ESR test has been automatically performed.

The ESR is governed by the balance between pro-sedimentation factors, mainly fibrinogen, and those factors resisting sedimentation, namely the negative charge of the erythrocytes (zeta potential). When an inflammatory process is present, the high proportion of fibrinogen in the blood causes red blood cells to stick to each other. The red cells form stacks called 'rouleaux,' which settle faster. Rouleaux formation can also occur in association with some lymphoproliferative disorders in which one or more immunoglobulin are secreted in high amounts. Rouleaux formation can, however, be a normal physiological finding in horses, cats, and pigs.

The ESR is increased by any cause or focus of inflammation. The ESR is increased in pregnancy or rheumatoid arthritis, and decreased in polycythemia, sickle cell anemia, hereditary spherocytosis, and congestive heart failure. The basal ESR is slightly higher in females.

History
This test was invented in 1897 by the Polish doctor Edmund Biernacki. In some parts of the world the test continues to be referred to as the Biernacki Test (Polish abbreviation: OB = Odczyn Biernackiego.) In 1918 the Swedish pathologist Robert Sanno Fåhræus declared the same and along with Alf Vilhelm Albertsson Westergren are eponymously remembered for the Fåhræus-Westergren test (abbreviated as FW test; in the UK, usually termed Westergren test), which uses sodium citrate-coagulated specimens.

Uses
Although it is frequently ordered, ESR is of limited use as a screening test in asymptomatic patients. It is useful for diagnosing diseases, such as multiple myeloma, temporal arteritis, polymyalgia rheumatica, various auto-immune diseases, systemic lupus erythematosus, rheumatoid arthritis, and chronic kidney diseases. In many of these cases, the ESR may exceed 100 mm/hour.

It is commonly used for a differential diagnosis for Kawasaki's disease and it may be increased in some chronic infective conditions like tuberculosis and infective endocarditis. It is a component of the PDCAI, an index for assessment of severity of inflammatory bowel disease in children.

The clinical usefulness of ESR is limited to monitoring the response to therapy in certain inflammatory diseases such as temporal arteritis, polymyalgia rheumatica and rheumatoid arthritis. It can also be used as a crude measure of response in Hodgkin's lymphoma. Additionally, ESR levels are used to define one of the several possible adverse prognostic factors in the staging of Hodgkin's lymphoma. There is also a wintrobe method.

The use of the ESR as a screening test in asymptomatic persons is limited by its low sensitivity and specificity. When there is a moderate suspicion of disease, the ESR may have some value as a "sickness index."

An elevated ESR in the absence of other findings should not trigger an extensive laboratory or radiographic evaluation.

Normal values
''Note: mm/hr. = millimeters per hour.''

Westergren's original normal values (men 3mm and women 7mm) made no allowance for a person's age and in 1967 it was confirmed that ESR values tend to rise with age and to be generally higher in women. Values are increased in states of anemia, and in black populations.

Adults
The widely used rule for calculating normal maximum ESR values in adults (98% confidence limit) is given by a formula devised in 1983:
 * $${\rm ESR}\ (mm/hr) \le \frac {{\rm Age}\ ({\it in\ years}) + 10\ ({\it if\ female})}{2}$$

ESR reference ranges from a large 1996 study with weaker confidence limits:

Children
Normal values of ESR have been quoted as 1 to 2 mm/hr at birth, rising to 4 mm/hr 8 days after delivery, and then to 17 mm/hr by day 14.

Typical normal ranges quoted are:
 * Newborn: 0 to 2 mm/hr
 * Neonatal to puberty: 3 to 13 mm/hr, but other laboratories place an upper limit of 20.

Relation to C-reactive protein
C-reactive protein is an acute phase protein produced by the liver during an inflammatory reaction. Since C-reactive protein levels in the blood rise more quickly after the inflammatory or infective process begins, ESR is often replaced with C-reactive protein measurement. There are specific drawbacks, however, for example, both tests for ESR and CRP were found to be independently associated with a diagnosis of acute maxillary sinusitis so in some cases the combination of the two measurements may improve diagnostic sensitivity and specificity.