The ESR blood test is commonly used to detect inflammation or infection in the body. It can help identify conditions ranging from mild infections, such as a cold, to more serious diseases like arthritis or acute pancreatitis.
Also known as the erythrocyte sedimentation rate, the ESR blood test measures how quickly red blood cells settle in a test tube. Faster settling can indicate inflammation, but the test does not identify the exact cause and is usually evaluated with other tests like CRP or a complete blood count (CBC)
ESR blood test results vary by age and sex and can be influenced by conditions such as infections, chronic diseases, or blood disorders. Understanding normal values and how to interpret high or low ESR levels helps guide further testing and clinical evaluation.
What is it for?
The ESR blood test helps detect or monitor inflammation or infection in the body by measuring how quickly red blood cells fall to the bottom of a tube of blood. When there is inflammation, certain proteins increase and make the cells sink faster, which leads to a higher ESR result.
Although the ESR blood test is very sensitive and can detect inflammation early, it is not specific. This means it cannot determine the exact cause, location, or severity of the condition. For this reason, doctors usually interpret ESR results along with other tests, such as a C-reactive protein (CRP) test or a complete blood count (CBC).
Test procedure
To perform the ESR blood test, a healthcare professional collects a blood sample and places it in a test tube. The sample is then observed to measure how long it takes for red blood cells to settle at the bottom.
The result is typically measured after 1 or 2 hours and reported in millimeters per hour (mm/h). No special preparation is required, and fasting is not necessary.
Reference values
Reference values for the ESR blood test vary by age and sex:
In clinical practice, the 1-hour result is considered the most relevant and is used more often.
Higher levels of inflammation are associated with higher ESR values. In some cases, such as rheumatologic diseases or cancer, ESR levels can exceed 100 mm/h.
Interpreting results
The ESR blood test result may indicate the following:
1. High ESR
A high ESR is commonly associated with infections, including viral or bacterial conditions such as the flu, sinusitis, tonsillitis, pneumonia, urinary tract infections (UTIs), or diarrhea.
It is also useful for monitoring diseases that cause significant inflammation, such as:
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Polymyalgia rheumatica, an inflammatory condition affecting the muscles
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Temporal arteritis, which affects blood vessels
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Rheumatoid arthritis, an inflammatory joint disease
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Vasculitis, inflammation of blood vessel walls
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Osteomyelitis, a bone infection
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Tuberculosis, an infectious disease
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Cancer
Other factors can also influence ESR results. Conditions that change blood composition or thickness, such as pregnancy, diabetes, obesity, heart failure, kidney disease, alcohol use, thyroid disorders, or anemia, may affect the result.
2. Low ESR
A low ESR result usually does not indicate a health problem. However, certain conditions can keep ESR levels unusually low and may interfere with detecting inflammation or infection.
These include:
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Polycythemia, an increased number of red blood cells
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Severe leukocytosis, a high white blood cell count
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Use of corticosteroids
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Hypofibrinogenemia, a blood clotting disorder
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Hereditary spherocytosis, a genetic form of anemia
Because ESR results are not always specific, healthcare providers interpret them based on the patient’s medical history and other test results. Additional tests, such as CRP, are often used because they provide more precise information about inflammation or infection.