ESRThe erythrocyte sedimentation rate
The erythrocyte sedimentation rate is the rate at which red blood cells in anticoagulated whole blood descend in a standardized tube over a period of one hour. It is a common hematology test, and is a non-specific measure of inflammation.
To perform the test, anticoagulated blood is traditionally placed in an upright tube, known as a Westergren tube, and the distance which the red blood cells fall is measured and reported in millimetres at the end of one hour.
Since the introduction of automated analyzers into the clinical laboratory, the ESR test has been automatically performed.
The ESR is influenced by the aggregation of red blood cells: blood plasma proteins, mainly fibrinogen, promote the formation of red cell clusters called rouleaux or larger structures. As according to Stokes' law the sedimentation velocity varies like the square of the object's diameter, larger aggregates settle faster. While aggregation already takes place at normal physiological fibrinogen levels, these tend to increase when an inflammatory process is present, leading to increased ESR.
The ESR is increased in inflammation, pregnancy, anemia, autoimmune disorders, infections, some kidney diseases and some cancers. The ESR is decreased in polycythemia, hyperviscosity, sickle cell anemia, leukemia, chronic fatigue syndrome, low plasma protein and congestive heart failure. Although increases in immunoglobulins usually increase the ESR, very high levels can reduce it again due to hyperviscosity of the plasma. This is especially likely with IgM-class paraproteins, and to a lesser extent, IgA-class. The basal ESR is slightly higher in females.
Stages
Erythrocyte sedimentation rate is the measure of ability of erythrocytes to fall through the blood plasma and accumulate together at the base of container in one hour.
# Rouleaux formation
# Sedimentation or settling stage
# Packing stage - 10 minutes
In normal conditions, the red blood cells are negatively charged and therefore repel each other rather than stacking. ESR is also reduced by high blood viscosity, which slows the rate of fall.
Causes of elevation
The rate of erythrocyte sedimentation is affected by both inflammatory and non-inflammatory conditions.
Inflammation
In inflammatory conditions, fibrinogen, other clotting proteins, and alpha globulin are positively charged, thus increasing the ESR.
Causes of reduction
An increased number of red blood cells causes reduced ESR as blood viscosity increases. Hemoglobinopathy such as sickle-cell disease can have low ESR due to an improper shape of red blood cells that impairs stacking.
Medical uses
Diagnosis
ESR can sometimes be useful in diagnosing diseases, such as multiple myeloma, temporal arteritis, polymyalgia rheumatica, various autoimmune diseases, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease 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 also elevated in subacute thyroiditis also known as DeQuervain's.
In markedly increased ESR of over 100 mm/h, infection is the most common cause, followed by cancer, kidney disease and noninfectious inflammatory disorders. Yet, in pneumonia the ESR stays under 100.
The usefulness of the ESR in current practice has been questioned by some, as it is a relatively imprecise and non-specific test compared to other available diagnostic tests. Current literature suggests that and ESR should be "obtained on all patients over the age of 50" who have an intense headache.
Disease severity
It is a component of the PCDAI, an index for assessment of the severity of inflammatory bowel disease in children.
Monitoring response to therapy
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.
Normal values
Westergren's original normal values made no allowance for a person's age. Later studies from 1967 confirmed that ESR values tend to rise with age and to be generally higher in women.
Values of the ESR also appear to be slightly higher in normal populations of African-Americans than Caucasians of both genders. Values also appear to be higher in anemic individuals than non-anemic individuals.
Adults
The widely used rule calculating normal maximum ESR values in adults is given by a formula devised in 1983 from a study of ≈1000 individuals over the age of 20: The normal values of ESR in men is age divided by 2; for women, the normal value is age plus 10, divided by 2.
Children
Normal values of ESR have been quoted as 1 to 2 mm/h at birth, rising to 4 mm/h 8 days after delivery,
Relation to C-reactive protein
C-reactive protein is an acute phase protein. Therefore, it is a better marker for acute phase reaction than ESR. While ESR and CRP generally together correlate with the degree of inflammation, this is not always the case and results may be discordant in 12.5% of the cases. CRP is a better marker for other autoimmune diseases such as polymyalgia rheumatica, giant cell arteritis, In some parts of the world the test continues to be referred to as Biernacki's Reaction. which uses sodium citrate-anti-coagulated specimens.
Research
According to a study released in 2015, a stop gain mutation in HBB gene was shown to be associated with ESR values in Sardinian population. The red blood cell count, whose values are inversely related to ESR, is affected in carriers of this SNP. This mutation is almost exclusive of the inhabitants of Sardinia and is a common cause of beta thalassemia.
According to a 2010 study, there is a reverse correlation between ESR and general intelligence in Swedish males aged 18–20.