What is ESR?
ESR or erythrocyte sedimentation rate is also called a sedimentation rate or Biernacki Reaction. The test was invented by the Polish doctor Edmund Biernacki.
ESR is a common test in hematology, a branch of pathology dealing in blood investigations and measures the rate at which red blood cells sediment in a period of 1 hour.
The erythrocyte sedimentation rate is a nonspecific test because increased results do not tell the doctor exactly where the inflammation is in the body or what is causing it, and also because it can be affected by other conditions besides inflammation.
For this reason, the ESR is typically used in conjunction with other tests.
Classically, the test is performed by two methods
Since the introduction of automated analyzers into the clinical laboratory, the ESR test is automatically performed.
The Westergren method requires collecting 2 ml of venous blood into a tube containing 0 .5 ml of 3.8 % sodium citrate.
It should be stored no longer than 2 hours at room temperature or 6 hours at 4 °C.
The blood is drawn into a Westergren-Katz tube up to the 200 mm mark. The tube is placed in a rack in a strictly vertical position for 1 hour at room temperature, at which time the distance from the lowest point of the surface meniscus to the upper limit of the red cell sediment is measured.
The distance of fall of erythrocytes expressed as millimeters in 1 hour, is the ESR.
The Wintrobe method is performed similarly to the Westergren method except that the Wintrobe tube is smaller in diameter than the Westergren tube and only 100 mm long.
The anticoagulant here is different. EDTA anticoagulated blood without extra diluent is drawn into the tube, and the rate of fall of red blood cells is measured in millimeters after 1 hour.
The shorter column makes this method less sensitive than the Westergren method because the maximal possible abnormal value is lower. However, this method is more practical for demonstration purposes.
Mechanism of ESR Test
The sedimentation rate of blood cells depends on the balance between pro-sedimentation factors, mainly fibrinogen, and the factors resisting sedimentation, namely the negative charge of the erythrocytes.
An inflammation causes an increase in the proportion of fibrinogen in the blood. This results in red blood cells sticking to each other to form stacks called ‘rouleaux,’ which settle faster and thus lead to higher ESR.
Rouleaux formation can also occur in association with some lymphoproliferative disorders in which one or more immunoglobulin are secreted in high amounts.
Significance of ESR Test
ESR has a limited role as a screening test in asymptomatic patients as the test itself has low sensitivity and specificity. Because the value rises in many conditions, the diagnostic ability of the test is of limited value. The test is more of suggestive value than diagnostic and the value is judged in correlation to symptoms and other parameters. If the ESR and clinical findings match, the doctor may be able to confirm or rule out a suspected diagnosis.
A single elevated ESR, without any symptoms of a specific disease, will usually not give the physician enough information to make a medical decision. Furthermore, a normal result does not rule out inflammation or disease.
Thus it is of some value in determining sickness in case of suspicion of the disease.
Increased Values of ESR
The ESR is increased by any cause or focus of inflammation. The ESR is increased in pregnancy and anemia.
However, a very high value of ESR has some diagnostic significance in conditions such as multiple myeloma, temporal arteritis, polymyalgia rheumatica, various auto-immune diseases, systemic lupus erythematosus, rheumatoid arthritis, and chronic kidney diseases, where it may exceed 100 mm/hour.
Also, ESR is frequently increased in some chronic infective conditions like tuberculosis and infective endocarditis.
ESR is also a component of the Pediatric Crohn Disease Activity Index (PCDAI), an index for assessment of the severity of inflammatory bowel disease in children.
ESR is helpful in diagnosing and monitoring therapy in temporal arteritis and polymyalgia rheumatica.
It can also be used as a crude measure of response in Hodgkin’s lymphoma. It is used to define one of the several possible adverse prognostic factors in the staging of Hodgkin’s lymphoma.
Decreased Values of ESR
- Congestive heart failure
- Hypofibrinogenemia (decreased fibrinogen levels)
- Low plasma protein (due to liver or kidney disease)
- Sickle cell anemia
- Hereditary spherocytosis
Normal Values of ESR
ESR values tend to rise with age and are generally higher in women. Higher values are often found in states of anemia.
ESR between the age of 20 to 90 years is 12-19 (mm/hr) in males and 18-23 (mm/hr) in females.
At birth, the value of ESR has been found as 1-2 and rises to 4 mm/hr 8 days after delivery and then to 17 mm/hr by day 14.
It varies between the range of 3-20 (mm/hr) till puberty.