Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and plasma viscosity (PV) blood tests are commonly used as inflammation tests.
If you have inflammation in a part of your body, then certain types of extra protein are often released from the site of inflammation and circulate in the bloodstream. Pathology laboratories use blood tests to assess if a person has inflammation happening. The tests are not very specific and many types of conditions can affect the blood result. More investigations may be needed to sort out the exact cause of the problem.
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Inflammation and blood proteins
Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and plasma viscosity (PV) blood tests are commonly used to detect an increase in protein in the blood. In this way, they are used as markers of inflammation.
3 Commonly Used Inflammation Tests
The information below is a general guide only. The arrangements and the way tests are performed may vary between different hospitals and pathology laboratories. Always follow the instructions given by your doctor.
ESR blood test (erythrocyte sedimentation rate)
A blood sample is taken and put in a tube that contains a chemical to stop the blood from clotting. The tube is left to stand upright. Red blood cells fall to the bottom of the tube gradually. measure,The clear liquid plasma is left at the top. The ESR measures the rate at which the red blood cells separate from the plasma and fall to the bottom of a test tube. The rate is measured in millimetres per hour (mm/hr). This is easy to measure, as there will be several millimetres of clear liquid at the top of the red blood after one hour.
If certain proteins cover red cells, these will stick to each other and cause the red cells to fall more quickly. So, a high ESR shows that you have some inflammation somewhere in the body.
Levels of ESR are higher in females. Also, the level increases with increasing age.
The normal value of the ESR Test
- ESR test normal range is 0-22 mm/hr for men and 0-29 mm/hr for women.
CRP blood test (C-reactive protein)
This is sometimes called an acute-phase protein. This means that the level of CRP increases when you have certain diseases,considers which cause inflammation. CRP can be measured in a blood sample. The CRP test measures the level of one specific protein, whereas the ESR considers many proteins.
The normal value of the CRP test
- CRP test, most people without no any underlying health problem have a CRP level less than 3 mg/L and nearly always less than 10 mg/L.
Plasma viscosity (PV)
The conditions under which the ESR test monitors can also be monitored by the PV test. It is another marker of inflammation. However, it is more difficult to perform and is not as widely used as ESR testing.
The normal value of the PV test
- PV test, the normal range for adults is 1.50-1.72 mPA.
These ‘normal ranges’ provide a guide. However, CRP, ESR and PV levels can vary with factors such as age, pregnancy and between different hospitals and pathology laboratories. The importance of the test result, therefore, needs to be considered in each person.
Learn about the d-dimer test
What are the conditions that affect the inflammation test?
Raised ESR, CRP, and PV levels are all markers of inflammation. PV and ESR do not change as rapidly as CRP does, either at the start of inflammation or as it goes away. CRP is not affected by as many other factors as the PV or ESR, making it a better marker of some types of inflammation. PV, however, is more sensitive and more specific than either ESR or CRP when monitoring the activity of rheumatoid arthritis.
ESR, CRP and PV can be raised in many inflammatory conditions, for example;
- Certain infections (mainly bacterial infections)
- Rheumatoid arthritis
- Various other muscular and connective tissue disorders – for example, polymyalgia rheumatica, giant cell arteritis or systemic lupus erythematosus
- Tissue injury and burns
- Some cancers, for example, myeloma and Hodgkin’s lymphoma
- Crohn’s disease
- Rejection of an organ transplant
- After operations
Some conditions lower the ESR, for example, heart failure, polycythaemia and sickle-cell anaemia. It is also lowered in conditions where your body has lower protein levels, for example, in some liver or kidney diseases.
When are these inflammation tests used?
- To help diagnose diseases
ESR, CRP and PV are nonspecific tests. A raised level means that ‘something is going on, but further tests will be needed to clarify exactly what that is. For example, you may be unwell, but the cause may not be clear. A raised ESR, CRP and PV may show that some inflammatory condition is likely to be the cause. This may prompt a doctor to do further tests to find the cause.
It is not usually possible to make a diagnosis of a certain condition just from a raised ESR, CRP, or PV level.
However, before you have further tests, your doctor may suggest that you have the ESR, CRP, or PV test repeated after a period of several weeks or months. If it has been raised by a recent infection (a very common cause) then it is likely to return to normal when your infection improves. You would not then need any further tests.
- To monitor the activity of certain diseases
For example, if you have polymyalgia rheumatica, the amount of inflammation and disease activity can partially be assessed by measuring one of these blood tests. The higher the level, the more active the disease. The response to treatment may also be monitored, as the level of ESR, CRP, and PV may fall if the condition is responding well to treatment.
All three tests are useful. However, changes in the CRP are more rapid. So, for example, a fall in the CRP within days of starting treatment for certain conditions is a useful way of knowing that treatment is working. This may be important to know when treating a serious infection or a severe flare-up of an inflammatory condition. For example, if the CRP level does not fall, it may show that the treatment is not working and may prompt a doctor to switch to a different treatment.
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