The erythrocyte sedimentation rate (ESR) test is one of the most commonly used laboratory tests in medicine to assess the presence of inflammation and disease in the body. Here, we will explain this concept and its analysis, as well as tools that can shed light on this topic.
As usual, we turn again to blood for answers to these kinds of inflammations: is it an infection, a tumour? or an autoimmune disease? While it will not directly diagnose a problem, it can give health care providers many clues as to what other tests to perform next or what guidelines to follow. This is why it is often requested and why it is necessary to know the results. Today we will look at what it consists of and what the results can mean. Here we go!
What is the erythrocyte sedimentation rate?
The essence of this test is to measure the rate at which red blood cells, also known as erythrocytes or red blood cells, drop or sediment (hence the name) when liquid is poured into a test tube. This tube is usually of the long, narrow type, which is likely to come to mind when we think of a laboratory tube.
How to interpret the results of this test?
Interpretation of the results is based on millimetres, measuring the amount of clear plasma remaining at the top of the tube after 1 hour. Under normal conditions, red blood cells are expected to descend gradually towards the bottom of the tube, slowly and mostly leaving a minimal amount of clear plasma at the top.
If a large number of these components are observed, we have to be a little ‘alert’, especially because there is also an increase in proteins called acute phase reactants. These are the ones that cause the red blood cells to fall in an extremely precipitous manner, which in turn increases the erythrocyte sedimentation rate. A reactant that we have already explained would be, as mentioned above, C-reactive protein or fibrinogen. Both of these components will increase in quantity if there is an inflammatory process developing.
What does inflammation entail?
This kind of ‘warning signal’ is an immune response of the body, warning us that something bad is happening. It can be relatively small or acute or develop slowly and over time, becoming chronic (autoimmune diseases or cancer).
However, the erythrocyte sedimentation rate test does not diagnose, it only provides general information about inflammation. It should be noted that the sedimentation rate can be elevated in many occasions and situations, so the cause needs to be further investigated.
Today we have slightly more specific tests that are able to reach a conclusion more quickly, so the use of erythrocyte sedimentation rate analysis is somewhat in disuse. However, it may be practical and necessary on certain occasions, such as in the diagnosis and monitoring of temporal arteritis, systemic vasculitis and/or polymyalgia rheumatica.
In addition, it is also necessary to take into account the fact that there are areas in the world that, unfortunately, do not have these new, more specific tests, so SGBV remains an excellent option until advances reach those areas.
There are cases in which the erythrocyte sedimentation rate, instead of being too high, is low, such as when there is inhibition of red blood cell sedimentation (polycythaemia or leukocytosis), as well as in certain protein disorders. Decreased values may also be observed in abnormalities of cell morphology (sickle cell anaemia).
As for the cases in which it increases more or less ‘naturally’ or within localisable causes, we can mention menstruation or pregnancy, moments of transitory increase in these values. In childhood, this test is often performed to diagnose and monitor possible cases of rheumatoid arthritis or Kawasaki disease.
When to order an erythrocyte sedimentation rate test?
This test has been performed for many years when information comes to light because, although it is not specific, it can provide information on the next steps to take, especially if the inflammation is suspected to be caused by an infection or cancer.
It is also very useful in monitoring the activity and response to treatment of the diseases discussed above; we also add systemic lupus erythematosus to this category.
When a fever occurs in a patient who does not have a complicated medical history and the cause is not understood, an erythrocyte sedimentation rate test can help clarify the cause, as well as for specific types of arthritis and symptoms affecting the muscles. It will be part of the list of tests that will need to be performed to confirm a diagnosis of the following conditions:
- Giant cell arteritis.
- Polymyalgia rheumatica.
- Rheumatoid arthritis.
Such an analysis is also very useful in managing and quantifying the severity of the inflammatory response and monitoring the treatment and the effect it is having on the disease and the patient. However, other ‘extra’ tests are often used to support a specific and accurate diagnosis and theory.
Results
As explained above, the results of the erythrocyte sedimentation rate analysis will give the distance in millimetres (mm) that the red blood cells have travelled in one hour (h). There are values considered normal or standardised: in men it is 0 to 22 mm/h and in women it is 0 to 29 mm/h.
As there are several reasons why the erythrocyte sedimentation rate may increase, the results of this test should be understood and compared with other tests performed. These figures will be interpreted by the attending physician taking into account the patient’s medical history and health status.
It is possible to have an increased erythrocyte sedimentation rate without further symptoms, in isolation. A more serious problem cannot be ruled out and should be investigated further. It should also be noted that, in addition to inflammation, elevated ESR may occur in anaemia, infections, pregnancy and in the elderly.
As there is a wide range of possibilities, it is best, depending on the individual’s own symptoms, to use additional tests. It is true that people with multiple myeloma or Waldenstrom’s macroglobulinaemia, 2 types of tumours that generate exaggerated amounts of immunoglobulins, have as a characteristic or symptom a very high ESR. In these cases there is no inflammation but the increase is due to the tumour itself.
1 hour after the test, the laboratory technician will take the reading of the erythrocyte sedimentation rate. Nowadays, depending on the laboratory equipment, the test can be read in about 20/30 minutes. However, there are also ‘rapid’ tests, which are incredibly useful in the emergency department, as they reduce the waiting time for patients by using a centrifugal method. In this case we would have the test results 5 minutes after setup.
Extra tests
We have been saying for quite some time now that there are or usually are tests in addition to the erythrocyte sedimentation rate. In addition to the ESR, the doctor will always ask for a metabolic study or haemogram, although C-reactive protein is also usually one of the tests of choice. When a severe infection is suspected, a haemogram is mandatory.
Both (ESR or CRP) are markers of inflammation, but the difference is that the former does not change or vary as rapidly at the onset or during inflammation as the latter does. However, the test is still necessary as an adjunct because, on the other hand, CRP is not affected by as many factors as ESR. The thing about the sedimentation test is that it is very easy to do: it is a simple blood test and does not even require fasting.
Some other complementary tests
Therefore, let’s look at what other tests are usually included when performing an erythrocyte sedimentation rate test:
- Antinuclear antibodies.
- Rheumatoid factor.
- Fibrinogen.
- Serum protein electrophoresis.
The increase in ESR is usually accompanied by the appearance of 2 proteins: globulins and fibrinogen (which also functions as a marker of inflammation). For this reason, the analysis of this protein is usually requested to measure it and an electrophoresis of serum proteins. In this way we can detect which of them, or if both, are responsible for the increased erythrocyte sedimentation rate.
This type of testing requires the experience, technology and passion of a laboratory team capable of performing clinical reference tests and managing them to be integrated into the operations of any other laboratory in an agile and flexible manner. At Ambar Lab has more than 3,000 laboratory tests and we offer you complete support in the management of your business and in the development of new projects.
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