Autoimmune diseases are chronic inflammatory disorders that occur when a patient’s own cells and tissues are attacked by their immune system. There are over 100 known autoimmune diseases, with a variety of presenting signs and symptoms depending on whether the abnormal immune response is systemic or if the target is a particular organ. 

The overall prevalence of autoimmune disease in the United States was recently estimated at 4.6%, somewhat below previous estimates.¹ In a study published last year, the authors explained the lower number offered may be due to a previous reliance on aggregates of disease-specific studies, which can overestimate prevalence because of the fact that a significant number of patients may have more than one autoimmune disorder. However, there is still a consensus that believes the incidence of autoimmune diseases are rising, especially for Graves Disease, celiac disease, and systemic rheumatic disorders.² They represent an increasingly significant burden on healthcare delivery globally.

Beyond the ANA

Many autoimmune diseases, especially organ-specific ones, have specific autoantibody markers. But the most commonly employed laboratory marker of autoimmune disease is the anti-nuclear antibody (ANA) test. This is usually performed using indirect immunofluorescence of cultured HEp-2 cells, although another approach utilizing a panel of autoantigens to detect specific antibodies may also be used. The indirect immunofluorescence approach is not standardized, and thus, different screening titers and the subjective nature of fluorescence microscopy may produce different results. 

Nevertheless, there is a consensus that the indirect immunofluorescent ANA remains the key tool in the initial evaluation of a patient presenting with signs and symptoms of a potential autoimmune disease. And, just as the prevalence of autoimmune disease has been increasing over the past few decades, so has the prevalence of positive ANA results.³ The ANA can detect a large number of autoantibodies, not just against nuclear antigens but also against antigens in the cell’s cytoplasm. Many of these have unknown clinical significance. So, although the ANA is very sensitive, it lacks specificity. A positive ANA, especially if low titer, may be seen in a variety of non-autoimmune disorders, and even in healthy individuals. One way to increase the specificity of the ANA is to increase the screening titer. In fact, although the majority of the laboratories in the United States use a 1:80 screening titer, higher titers such as 1:100 or even 1:160 are common in other parts of the world.⁴ But this compromises sensitivity.

A better approach may be to assay many of the important specific anti-nuclear antibodies associated with autoimmune diseases in addition to the immunofluorescent ANA. These include anti-dsDNA and anti-Sm (both strongly associated with systemic lupus erythematosus), anti-Scl70 and anti-centromere (both associated with progressive systemic sclerosis) and anti-SSA and anti-SSB (both associated with Sjogren Disease). Several studies have shown that combining the ANA with immunoassays for specific anti-nuclear antibodies is effective and can increase accuracy significantly. This can be done as a reflex, when the ANA is positive, or even done if the ANA is negative, because some important anti-nuclear antibodies may not be detected by indirect immunofluorescence. As an example, one study found that combining both approaches to screening increased the sensitivity of the 1:80 indirect immunofluorescence screen from 89% to 97%, while maintaining the 98% specificity of the immunoassay screen.⁵

If a physician is seeking enhanced accuracy when screening for autoimmune disease, it may also be important to include other autoantibodies not associated with ANA. For instance, the most prevalent autoimmune rheumatic disease is rheumatoid arthritis (RA). But the ANA is positive in only a minority of RA patients. Therefore, adding specific RA markers to a profile will help to identify this important disorder. 

New tools aimed at making testing simpler and smarter are available. For example, at Quest Diagnostics, the ANAlyzeR ANA IFA with Reflex Titer/Pattern panel includes specific anti-nuclear antibodies, several RA markers, as well as additional antibodies to identify other relatively common diseases seldom associated with ANA, like Graves Disease. This test screens for 25 autoantibodies in a single profile, allowing for a comprehensive view of the patient’s risk of autoimmune disease. Previous research found that 24.4% of patients with one autoimmune disease had another, 7.8% had 3, and 2.4% had 4 or more.¹ Consequently, casting a wide autoantibody net may make sense, especially when the patient’s signs and symptoms are vague or overlapping. At the same time, if a physician is interested in a specific autoantibody, most are also individually orderable.

Focus on primary care

The need to identify autoimmune disease as soon as possible is important. Early intervention, especially in systemic rheumatic disorders such as rheumatoid arthritis, can have a significant impact on disease outcome. Increasingly, the burden of identifying autoimmune diseases is falling onto primary care providers. There is a significant shortage of rheumatologists nationwide, and delay in referrals may exceed six months. 

Also, using ANA only to decide to refer to a rheumatologist may result in unnecessary referrals, increasing wait times, driving up costs, and leading to provider burnout.⁶ Autoimmune disease profiles can therefore help the primary care physician identify those patients who truly need referral so that they may get the early treatment they need sooner.

Conclusion

The surge in autoimmune disease prevalence demands a fundamental shift in how physicians approach initial screening. Relying on traditional testing such as ANA alone will prolong the patient’s journey and prevent early intervention. By assessing multiple disease-specific markers alongside ANA, primary care physicians can better evaluate patients, avoid unnecessary specialist referrals, and ensure timely interventions.

REFERENCES

1. Abend AH, He I, Bahroos N, et al. Estimation of prevalence of autoimmune diseases in the United States using electronic health record data. J Clin Invest. 2024;135(4):e178722. doi:10.1172/JCI178722. 
2. Conrad N, Misra S, Verbakel JY, et al. Incidence, prevalence, and co-occurrence of autoimmune disorders over time and by age, sex, and socioeconomic status: a population-based cohort study of 22 million individuals in the UK. Lancet. 2023;401(10391):1878-1890. doi:10.1016/S0140-6736(23)00457-9.
3. Dinse GE, Parks CG, Weinberg CR, et al. Increasing prevalence of antinuclear antibodies in the United States. Arthritis Rheumatol. 2020;72(6):1026-1035. doi:10.1002/art.41214. 
4. Wener MH, Fink SL, Morishima C, Chaudhary A, Hutchinson K. Anti-nuclear antibody quantitation: Calibration and harmonization adjustment via population interrogation. J Appl Lab Med. 2022;7(1):46-56. doi:10.1093/jalm/jfab142. 
5. Bizzaro N, Brusca I, Previtali G, et al. The association of solid-phase assays to immunofluorescence increases the diagnostic accuracy for ANA screening in patients with autoimmune rheumatic diseases. Autoimmun Rev. 2018;17(6):541-547. doi:10.1016/j.autrev.2017.12.007. 
6. McGoldrick J, Molina-Ochoa D, Schwab P, Edwards ST, Barton JL. An evaluation of burnout among US rheumatology fellows: A national survey. J Rheumatol. 2023;50(9):1185-1190. doi:10.3899/jrheum.221114.