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Testing for Autoimmune Diseases
Autoantibodies can be specific markers for autoimmune diseases and are a key component in the diagnosis of diseases which are often underestimated and difficult to determine. When a patient's clinical presentation offers a wide range of diagnostic possibilities, testing can be used to help confirm or rule out multiple autoimmune diseases, making it a valuable tool in getting your patients the treatment they need. Shortening the time from initial presentation to diagnosis could mean you and your patients are spared years of visits, ineffective treatments and frustration. Evidence-based treatment can also help reduce costs and improve diagnoses and referrals.
The role of testing to aid in diagnosis
Diagnosis is most often based on a compilation of clinical information, laboratory testing and, in some cases, imaging tests, biopsies or endoscopies. Laboratory tests performed to aid in the diagnosis of autoimmune disorders depend on the particular disorder the healthcare professional suspects a patient has, but usually include blood tests for one or more autoantibodies as well as tests for inflammation such as C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR).
BENEFITS OF BLOOD TESTING IN AUTOIMMUNE DISEASES DIAGNOSIS
If you suspect that a patient has a certain autoimmune disease, diagnostic testing can help confirm the diagnosis. Using serological testing to identify autoimmune disease biomarkers can help you provide patients with a timely, accurate diagnosis, which has the potential to slow the progression of their disease and offer them the opportunity for symptom management.
Some other notable reasons to incorporate testing in your diagnostic process include:
1. Detecting autoantibodies early
Early diagnosis and intervention can slow or even halt the progression of symptoms in some autoimmune diseases. In Rheumatoid Arthritis (RA), for example, the presence of specific autoantibodies, individually or in combination, increases the likelihood of disease.1 Serological testing is specific enough to allow the early identification of autoantibodies, leading to earlier diagnosis and the acceleration of treatment.
2. Broadening your diagnostic range
Currently, immunoassays are available to detect autoantibodies related to autoimmune conditions, such as connective tissue diseases, rheumatoid arthritis, gluten-related disorders (including celiac disease), thyroid disease, antiphospholipid syndrome, vasculitis, Goodpasture syndrome and autoimmune liver diseases. Dozens of fully automated assays are available, with steady expansion of the test menu.
3. Minimizing invasive diagnostic procedures
Utilizing testing can change the diagnostic process from one of exploration to one of precision. For example, celiac disease has a set of very sensitive and specific markers. A combination of specific blood tests can virtually rule out or confirm the disease with close to 100% certainty.2 Including serologic markers in the diagnosis of celiac may decrease the need for small- intestine biopsies which can be expensive and unpleasant—especially for children. Waiting for a biopsy may also prolong the final diagnosis.
The role of sensitivity and specificity in the diagnosis of AI diseases3
It is important to strike the right balance between sensitivity and specificity – whether within one assay or through a combination of assays.
The ability to make a diagnosis or screen for a condition depends both on the discriminatory value of the test and on the prevalence of the disease in the population of interest. Autoimmune diseases have, in general, low prevalence. When testing for diseases with low prevalence, it is crucial to have diagnostic tests with high clinical specificity to secure a correct diagnosis with minimal numbers of false positive results.
- A marker with high specificity occurs in only one disease, i.e. antibodies against tissue transglutaminase (tTG)
- A marker with high sensitivity is detectable in all or most patients with a particular disease; CCP2 antibodies in Rheumatoid Arthritis are a good example of a marker with high sensitivitiy
- A disease marker can be highly sensitive, but not very specific, such as antibodies to cardiolipin, which are a marker for antiphospholipid syndrome but are also detectable in other diseases
- A disease marker can be highly specific but have low sensitivity, such as anti-Sm antibodies, which are found in 10-50% of SLE patients but almost never in other diseases4
Test results with high clinical value are the basis of clinical decisions and the key for diagnostic success.
Advanced techniques are used such as recombinant gene technology to develop the latest in standardized, precise, reliable and easy-to-use diagnostic tests. To ensure the highest quality of autoantibody tests, it is crucial to use very pure, conformationally correct antigens.
It is, of course, important to interpret results in the context of the patient history and clinical findings.
How AI diseases can manifest over time
There are more than 120 types of autoimmune diseases,5 and some have similar symptoms. Inflammation is the common trait, but presentation can vary widely from one condition to another, and even within the same disease. Because these conditions tend to affect multiple systems, their symptoms can be misleading, which slows down the process towards an accurate diagnosis.
Bas S, et al. Anti-cyclic citrullinated peptide antibodies, IgM and IgA rheumatoid factors in the diagnosis and prognosis of rheumatoid arthritis. Rheumatology. 2003;42:677–680
Murray JA, Herlein J, Mitros F, et al. Serologic Testing for Celiac Disease in the United States: Results of a Multi-laboratory Comparison Study. Clin Diagn Lab Immunol. 2000;7(4):584–587.
McGee DL. Understanding Medical Tests and Test Results. http://www.merckmanuals.com/professional/special-subjects/clinical-decision-making/understanding-medical-tests-and-test-results. Accessed December 2017.
Arroyo-Ávila M, Santiago-Casas Y, McGwin G, et al. Clinical associations of anti-Smith antibodies in PROFILE: a multi-ethnic lupus cohort. Clinical Rheumatology. 2015;34(7):1217-1223. doi:10.1007/s10067-015-2941-y.
American Autoimmune Related Diseases Association. https://www.aarda.org/news-information/statistics/#1488234345468-3bf2d325-1052. Accessed November 2017.
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