Sed rate test commonly refers to the ESR test – Erythrocyte Sedimentation Rate. The primary purpose of this blood test is to show whether there is any inflammation in your body and is therefore, used to diagnose and check the growth of an inflammatory disease. It is rarely used as a tool to diagnose diseases on its own.

What Is Sed Rate Test?

The sed rate test is used to indirectly determine the degree of inflammation. To perform the test, a test tube of anti-coagulated blood is observed; the rate at which red blood cells set to the bottom of the test tube is measured in mm/h. The greater the number of red blood cells settling at the bottom in one hour, the higher the erythrocyte sedimentation rate is. If there is inflammation present in the patient’s body, proteins are produced by the immune system and the liver that cause the erythrocytes to clump together.

Purposes of Sed Rate Test

A sed rate test is never used on its own to diagnose a disease, monitor the spread of disease or check for inflammation because it cannot determine the exact factor causing inflammatory activity. Therefore, it is normally used in conjunction with other kinds of tests, such as C-reactive protein (CRP) test.

Sed rate tests are carried out for the following purposes:

• To reveal whether any inflammation is present in the body
• To determine whether or not the treatment is working
• To check the growth of a disease

Doctors often carry out sed rate tests when the following diseases are suspected:

• Rheumatoid arthritis
• Giant cell arthritis
• Polymyalgia rheumatica

Results of Sed Rate Test

Normal Range

The following table shows the normal range of values within which the results of the sed rate test should lie for an average healthy individual of four different sets: men, women, children and newborn children.

High Value

In certain patients, the results of the sed rate test may acquire a higher value that lies outside of the normal range for their respective group of people. Sedimentation rates may be higher because of the following factors:

• Autoimmune diseases, for example, rheumatoid arthritis and systemic lupus erythematosus
• Chronic kidney diseases
• Cancer, for example, multiple myeloma and lymphoma
• Viral infections
• Various infections, for example, appendicitis, pneumonia and pelvic inflammatory disease
• Infections of the kidney, joints, skin, bones or heart valve
• Thyroid gland inflammation, which is known as Graves’ disease
• Inflammation of blood vessels, for example, giant cell arthritis
• Inflammation of joints, for example, polymyalgia rheumatica
• Pregnancy
• Toxemia of pregnancy, which is called preeclampsia

Low Value

Carrying out the sed rate test on certain patients may yield low values, which lie below the normal range of values for their respective group. Low values of sedimentation rates can be caused due to several reasons, such as:

• High levels of blood sugar
• Liver disease
• Polycythemia
• Sickle cell disease

Influencing Factors

In certain conditions, doctors either do not perform the sed rate test or performing the test yields inaccurate results. This may be so in the following cases:

• A patient suffering from anemia
• A patient currently undergoing her menstrual period
• A pregnant patient
• The sed rate is higher in older people.
• Certain kinds of medication may also influence the result of the test.

Cautions

• A sed rate test is not completely reliable. Although it is used to determine whether there is any inflammation in the body and thus, diagnose different diseases, there are certain diseases that have very little or no effect on the sed rate. In this case, even though the patient will have the disease, the results of the sed rate test will lie within a normal range.
• Doctors should not solely rely on the sed rate test to determine whether or not the patient is suffering from a disease. This is because the test cannot point the exact causal factor.
• Doctors normally use the sed rate test in conjunction with several other kinds of tests. For example, they might use the C-reactive protein (CRP) blood test to check for any inflammation in the body.