Autoimmune conditions are a group of disorders in which the immune system mistakenly attacks the body’s own cells and tissues, causing diseases such as rheumatoid arthritis, inflammatory bowel disease, and celiac disease. Diagnosing autoimmune diseases can be challenging due to their complex nature and varied symptoms, which often overlap with other conditions. One useful tool health care professionals use when diagnosing an autoimmune condition is detecting the presence of autoantibodies in a patient's blood. In this article, we’ll discuss what autobodies are and 5 ways they are used to diagnose and manage autoimmune disease.

What Is an Autoantibody?

Before talking about autoantibodies, let’s first talk about antibodies. An antibody is a protein made by your immune system (specifically, your white blood cells) that protects you from foreign invaders that can hurt you, such as bacteria, fungi, and viruses. When a microbial threat is detected, antibodies can both inactivate the invader and also call other components of the immune system to help protect you from the invader. This process plays a critical role in your body’s immune response and defense against infection and disease. (Source)

Autoantibodies are antibodies produced by the immune system when it has trouble differentiating between a foreign substance and the body itself. Your immune system mistakes your own tissues and cells for invaders, and tries to protect you by producing autoantibodies that target those tissues and cells. These autoantibodies can then lead to inflammation and damage, and can eventually result in symptoms of autoimmune disease. (Source)

There are many different types of autoantibodies, and depending on the type of disease, different autoantibodies will target different types of cells and tissues. For example, in rheumatoid arthritis, the autoantibodies primarily target the joints, while in Hashimoto’s disease they target cells in the thyroid gland. Autoantibodies can also also be found in people with cancer, and are emerging as potential biomarkers for cancer diagnosis. (Source) 

Now that we know what autoantibodies are, let's look at why they are measured in the context of autoimmune diseases. 

Why Are Autoantibodies Measured in Autoimmune Disease?

If you have autoimmune-related symptoms, health care professionals can discover important information about your autoimmune disease by measuring autoantibody levels in your blood  through a simple blood test. It’s important to note that studies have found that many people have autoantibodies without having autoimmune symptoms. But if your health care provider does suspect you may have an autoimmune condition, here are 5 ways autoantibodies can be used to diagnose and manage autoimmune diseases.

1. Disease Specificity

Autoantibodies can be highly specific to certain autoimmune diseases, and the presence or absence of a specific autoantibody can help narrow down a diagnosis. For example, anti-nuclear antibodies (ANA) are found in 95% of patients with systemic lupus erythematosus (SLE); this means that if your results are negative for ANA, it’s unlikely you have lupus.

Another example is the presence of the thyroglobulin antibody (TgAb), which is present in up to 80% of patients with Hashimoto’s disease and is, therefore, a strong indicator of that condition. Importantly, the presence of specific autoantibodies does not in itself mean you have an autoimmune disease. Instead, knowing the antibody exists can help your health care provider narrow down the potential diagnosis and guide further testing. (Source, Source)

2. Disease Severity

Autoantibodies can also provide information about disease severity and prognosis. For example, if a patient with rheumatoid arthritis has anticyclic citrullinated protein antibodies (anti-CCP antibodies), this suggests they have more severe joint damage and a worse prognosis than if they don’t have the antibodies. In SLE, the presence of anti-double-stranded deoxyribonucleic acid antibodies (anti-dsDNA autoantibodies) is associated with more severe kidney involvement and a worse prognosis. (Source, Source, Source, Source)

3. Early Detection

Autoantibodies can sometimes be in your blood years before you begin to have symptoms of an autoimmune disease. This means the detection of specific autoantibodies can help with early diagnosis and early treatment of autoimmune diseases. For example, anti-Sjögren's-syndrome-related antigen A (anti-SSA) and anti-Sjögren's-syndrome-related antigen B (anti-SSB) antibodies can be detected in the blood of patients with Sjögren’s syndrome years before they develop standard symptoms of dry eyes and dry mouth. Early detection can have a big impact as, in some autoimmune conditions, early treatment can slow down the progression of the disease. (Source, Source)

4. Pharmacological Treatment Guidance

Autoantibodies can also be helpful for guiding treatment choice, by providing information on which drugs you may respond to best. For example, for patients with rheumatoid arthritis the drug abatacept is more effective in those who are positive for the autoantibodies rheumatoid factor (RF) and/or anti-CCP, compared to patients who are negative for these autobodies. This means testing for these antibodies before starting treatment can identify how likely you are to benefit from abatacept. This test is recommended by the American College of Rheumatology to guide treatment choice for patients with rheumatoid arthritis. (Source, Source)

5. Disease Differentiation

Autoantibodies can also help differentiate between autoimmune diseases that may have similar clinical symptoms. For example, as we mentioned above, testing for ANA is common when your health care provider suspects you may have lupus. However, if ANA antibodies are present in your blood, this isn’t enough for a diagnosis, as only about 13% of people with a positive ANA test actually have lupus. ANA can also be a sign of Sjögren’s syndrome, juvenile arthritis, scleroderma, and polymyositis and dermatomyositis. To further narrow down a diagnosis, the health care provider will order additional autoantibody tests. (Source)

Detection of multiple autoantibodies can cumulatively suggest one autoimmune disease over another. For example, the thyroid antibody TgAb is present in 60%–80% of patients with Hashimoto’s disease and 50%–60% of patients with Graves’ disease, so a test that is positive for TgAb could mean either Hashimoto’s or Graves’. However, the presence of the thyrotropin receptor antibody (TRAb) in addition to TgAb can help narrow down the diagnosis to Graves’ disease. (Source, Source, Source)

The presence or absence of autoantibodies can also help differentiate between autoimmune and non-autoimmune versions of the same condition. For example, many diseases have the symptoms of vitamin B12 deficiency and chronic stomach inflammation (known as atrophic gastritis), but when these symptoms occur along with autoantibodies, this suggests the individual may have an autoimmune condition called pernicious anemia. (Source, Source)

The Bottom Line 

Autoantibodies are an important tool in diagnosing and managing autoimmune diseases. The presence or absence of these proteins in your blood can provide useful information about disease specificity, prognosis, and treatment response, while also helping with early diagnosis and differentiation between similar conditions. The detection of autoantibodies can help guide further testing and treatment, leading to better outcomes for patients with autoimmune diseases. 

Making sense of all the terminology, diagnostic tools, and treatments for autoimmune conditions can be overwhelming. If you’re looking for additional education and support in managing your autoimmune symptoms, the experts at WellTheory are here to help. The WellTheory care team can develop a personalized care plan while also providing expert-led masterclasses and office hours to help decipher all the complexities of living with an autoimmune condition.   

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