The extractable nuclear antigen (ENA) blood test helps to detect the presence of autoantibodies that are within the proteins of the nucleus of a cell. The reason why these proteins are referred to as being extractable is because they can be removed from the cell with the use of saline. These autoantibodies are produced by the immune system and mistakenly recognize parts of the body as being an invader that needs to be eliminated.
Some autoimmune disorders are specifically associated with the presence of one or more than one ENA autoantibodies. This association, along with the results from an ENA blood test, can help doctors be able to diagnose the presence of an autoimmune disorder or determine which disorder may be present. Most ENA blood tests are a 4 test panel that includes Anti-RNP, Anti-Sm, Anti-SS-A, and Anti-SS-B autoantibodies.
Depending on the signs and symptoms being experienced, a medical provider may recommend a 6 panel test instead. The expanded ENA blood test will look for Scl-70 and Anti-Jo-1 autoantibodies in addition to those found in the 4 test panel.
When To See a Doctor About the ENA Blood Test
The most common symptom experienced with the presence of an autoimmune disorder is persistent inflammation. It may occur anywhere within the body, but is typically confined to one fairly specific location that the autoantibodies have mistakenly identified as an invading bacteria, virus, or other foreign body. There may also be signs of tissue damage, ongoing fatigue that cannot be explained, or unusual changes in weight.
Depending on the autoimmune disorder that is being evaluated, there may be a number of additional symptoms that should be evaluated by a medical provider. This includes a persistent fever, muscle or joint pain, swelling in the muscles or joints, a skin rash, and sensitivity to light. Some people may notice a foamy urine, which indicates the presence of protein. There may also be a sensitivity to the cold.
In most cases, the first test ordered will be the ANA blood test. If that comes back as being positive, then the ENA blood test will be ordered. If the ANA blood test comes back as negative, then the ENA blood test is not typically requested.
What Do My ENA Blood Test Results Mean?
Because the ENA blood test is a panel of tests, each specific autoantibody being looked at will either come back with a positive or a negative result. Based on these findings, a medical provider may be able to diagnose a specific autoimmune disease. A positive Anti-RNP result, for example, can be seen in at least 95% of instances where mixed connective tissue disease is the suspected culprit, as well as systemic lupus or scleroderma.
Systemic lupus may also be diagnosed with the presence of the Anti-Sm autoantibody. It’s a very specific antibody marker for this particular disease. Polymyositis or Sjorgen’s syndrome can also be detected with positive blood test results.
If the ENA blood test is negative, but the ANA blood test is positive, then the combination of results may lead to additional testing or a diagnosis based on personal signs and symptoms.
There are more than 100 antigens that have been identified as being extractable, but it is only these 6 that are routinely tested. Each result can only be interpreted by the attending doctor.
Here’s What You Need to Know
ENA autoantibodies will not go away once they have been created. They may be reduced in number to prevent serious symptom development, but once there is a positive test result, a person will always test positive.
ENA blood tests can only be evaluated by a specific laboratory. Some hospitals are equipped to perform this test, but not every medical provider will have access to this test. Because of this, there may be a need to either ship the blood draw to the closest laboratory or have a patient travel to the location where testing occurs. This may result in a delay to receive results of up to 5 business days.
The 4 test panel is usually the one doctors will order. This does not mean something will be missed. Additional tests can be ordered separately to make sure a full picture of health is obtained.
The ENA blood test is only ordered when there is a suspicion of an autoimmune disorder, typically confirmed in part by the presence of a positive ANA blood test. Most people will never have this test ordered for them. For those that do, this information can help to interpret the results effectively so that a treatment plan can be developed with their consulting doctor.