Erythrocyte sedimentation rate: what is it?

Clinical laboratory tests are of great importance in medical practice. Sometimes these are the only way to confirm the presence of a disease. One of the most frequently performed tests is the erythrocyte sedimentation rate.

Also known as erythrocyte sedimentation rate, VSG or ESR for its acronym in English, is a test that measures how quickly red blood cells settle to the bottom of a test tube. A higher or lower sedimentation rate than usual indicates the presence of different pathologies.

Under normal conditions, erythrocytes or red blood cells have a negative charge, which causes them to repel each other, with a sedimentation rate of 10 millimeters (mm) per hour. However, it may vary depending on the subject of study and their lifestyle.

Reasons why SGBV should be performed

The erythrocyte sedimentation rate is a test that guides the specialist and can indicate the existence of diseases. In this sense, it can be useful in the presence of any of the following situations:

  • Fever of unknown origin.
  • Some types of arthritis.
  • Symptoms affecting the muscles.

However, the doctor must analyze the clinic presented by the patient together with the results of the laboratory tests in order to give an accurate diagnosis. On the other hand, ESR can be used as an important diagnostic criterion for two diseases: polymyalgia rheumatica and temporal arteritis, both of which are very rare and appear in patients over 50 years of age.

Polymyalgia rheumatica is an inflammatory disease that affects the proximal muscles of the extremities and torso, causing pain and limiting movement. While temporal arteritis causes headache, decreased visual acuity, fever, jaw claudication and anemia.

ESR is a test that doctors may order when there is muscle or bone pain.

You can also read: How do I know if I have anemia?

How should I prepare for this test?

This is a fairly simple and quick test, so it will not be necessary to have any type of extraordinary preparation. If only one erythrocyte sedimentation rate is performed, it is not an essential requirement to be fasting, but if other analyzes are done at the same time, the pertinent measures must be taken.

In order to perform the test, venous blood must be drawn with a syringe. The prick is done in the arm. This can cause mild pain or discomfort during the exam, which sometimes remains for the rest of the day. However, it does not prevent the performance of daily activities.

Blood analysis is very simple and is usually done using the Westergren method, in which 2 ml of blood are mixed with 0.5 ml of citrate in a test tube and the erythrocyte free distance is measured. After one hour, the distance in mm from the area without red blood cells is recalculated to determine the speed at which they descended.

Significance of a high erythrocyte sedimentation rate

When the sedimentation rate is above normal values the presence of pathologies that occur with inflammation and some neoplasms should be suspected. According to studies, the rate increases after 24 hours and does not usually return to normal values ​​until after its resolution.

This type of pathology increases the concentration of various proteins in the blood plasma. All of these proteins, especially fibrinogen, will affect the charge on the surface of the red blood cells, causing them to descend faster.

However, various situations that increase fibrinogen in the blood, such as pregnancy, diabetes or end-stage renal failure are capable of increasing the erythrocyte sedimentation rate. Among other causes we can mention the following:

  • Anemia.
  • Macrocytosis
  • Acute hemorrhage
  • Acute myocardial infarction.
  • Lymphoma
  • Metastatic carcinoma.

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Significance of a low erythrocyte sedimentation rate

Most of the time, a low sedimentation rate is of little medical relevance. In this sense, it can reach 0 mm in normal patients, so it is not usually a cause of concern for specialists.

However, a low erythrocyte sedimentation rate (between 0 mm and 3 mm) is associated with various health problems, including the following:

  • Polyglobulia or large number of red blood cells.
  • Deformations in red blood cells.
  • Hyperviscosity syndromes.
  • Smoking habit.
  • Heart failure.

As if that were not enough, infectious diseases such as dengue can cause a slight decrease in the sedimentation rate. This fact was demonstrated in a study in which the ESR of patients with the pathology was very low compared to others with acute febrile syndromes.

Although rare, low ESR can be caused by dengue, an infectious tropical disease transmitted by mosquitoes.

A simple, but efficient test

As you can see, erythrocyte sedimentation rate is not a complex test, however it is very useful when looking for the presence of diseases that cause inflammation. It can guide the doctor and help him make an accurate diagnosis.

As for the patient, he should not have any special preparation to perform it. In addition, after the procedure you will be able to continue with your daily activities without any inconvenience.