ESR
Meaning of ESR: An old, inexpensive blood test that reports something is wrong somewhere without saying what or where.
Definition of ESR
ESR stands for erythrocyte sedimentation rate, the distance red blood cells fall through a column of blood in one hour. Inflammation raises the level of certain proteins that make red cells stack together, and heavier stacks sink faster. A raised rate signals inflammation somewhere in the body but gives no indication of its cause or its location.
How does the test work?
Blood treated to stop it clotting is drawn into a narrow vertical tube and left standing for an hour. Red cells are denser than the fluid around them and settle downward, leaving clear plasma above. The height of that clear column is the result. Individual erythrocytes settle slowly because they repel each other, each carrying a negative surface charge. Certain proteins released during inflammation, fibrinogen above all, neutralize that repulsion so the cells stack face to face in columns resembling piles of coins. A stack is heavier relative to its surface area than a single cell, so it falls faster.
What raises it and what lowers it?
| Raises the rate | Lowers the rate |
|---|---|
| Infection and inflammatory disease | Very high red cell count |
| Some cancers, particularly myeloma | Abnormally shaped cells, as in sickle cell disease |
| Anemia and pregnancy | Very high white cell counts |
| Older age and kidney disease | Severe heart failure |
How does it compare with C-reactive protein?
Both point to inflammation, but they behave differently over time. C-reactive protein is made by the liver within hours of an inflammatory stimulus and falls away just as quickly once the stimulus stops. The sedimentation rate depends on proteins that accumulate over days and clear over weeks, so it lags at both ends. That lag is sometimes an advantage, since a rate measured after an acute illness has settled still reflects the preceding weeks. It is also affected by the number and shape of the red cells themselves, which the protein measurement is not.
Where is it particularly used?
It retains a defined place in suspected giant cell arteritis and polymyalgia rheumatica, where a markedly raised rate supports the diagnosis, and in following the activity of some rheumatic diseases over time. As a general screening test in someone with vague symptoms it performs poorly, since a normal result does not exclude serious disease and a raised one points nowhere in particular.
Also known as
Used in a sentence
An elevated ESR prompted further investigation for an inflammatory cause.
Good to know
The result is nonspecific and is influenced by age, anemia and red cell shape as well as by inflammation, so it neither confirms nor excludes a particular diagnosis.
Word origin
Where “ESR” comes from
Erythrocyte joins the Greek erythros, meaning red, to kytos, meaning cell.