Using the antinuclear antibody test to diagnose rheumatic diseases: when does a positive test warrant further investigation?

Frequency of Repeating Antinuclear Antibody Testing: When Less Is More

Objectives Antinuclear antibodies (ANA) are autoantibodies that are associated with and ordered to diagnose autoimmune connective tissue disease. ANA have high sensitivity (~98%) but low specificity (~75%), and because they can be found in healthy individuals and non-rheumatologic conditions leading to their elevation, ANA tests are often requested and interpreted inappropriately by clinicians. The aim of this study was to retrospectively assess how frequently ANA testing is repeated in the adult population of Saudi Arabia (SA) and which factors are associated with and lead to inappropriate testing. Methodology We investigated a study group of 40,634 adult patients who underwent 229,825 ANA tests from 2018 to 2022 in an academic hospital in Jeddah, SA. We took a random sample of 500 patients from the study group, along with their 998 ANA tests, to look in depth into our research questions. Variables related to patients, ANA tests, and ordering physicians were collected. Descriptive and analytical statistics were employed to address the research questions, and a p-value < 0.05 was considered statistically significant. Results We found 57% of the ordered ANA tests to have positive results, with the most common titers of mild positivity being 1:80 and 1:160. Most repeated ANA tests were ordered with an interval of more than one year, and when repeated, 67% of test results remained unchanged. The majority of seroconversions resulted from negative ANA tests or those with weak (titer 1:40) or mild positivity (titer 1:80-1:160). The results of the moderate (titer 1:320-1:640) and strong (titer ≥1280) positivity ANA tests did not change. Only 11% of repeated ANA tests were found to be appropriate for repetition. The most common specialties associated with ordering ANA tests in general were internal medicine, followed by rheumatology, and finally family medicine. Our correlation analysis revealed that being female, having systemic connective tissue disease, and having a rheumatologist as a specialist were all associated with ordering more than 10 ANA tests (p < 0.05). Conclusion Because the results of repeated ANA tests did not change much, our study suggests that the cost of repeating ANA tests and the subsequent potentially unnecessary interventions should all be carefully examined before scheduling a repeated ANA test. Further studies involving patients from SA and across wider healthcare settings (academic, community, and private hospitals and healthcare centers) are warranted.

The Frequency of Immunofluorescence Antinuclear Antibody Patterns and Extractable Nuclear Antigen: Experience From a Large Laboratory in Pakistan

Background Autoimmune disorders have shown an increasing incidence in the last few years. The systemic response to the disorder is characterized by the expression of antinuclear antibody (ANA), which serves as the serological hallmark of autoimmunity. Its presence may indicate either a systemic autoimmune disease such as systemic lupus erythematosus (SLE), scleroderma, and polymyositis/dermatomyositis or an organ-specific condition such as autoimmune thyroiditis and hepatitis. The systemic response may vary from one individual to another in each population. Several specific autoantibodies are also found to be associated with specific rheumatic diseases. Aim We aim to report the frequency of ANA positivity, ANA immunofluorescence patterns, and the presence of extractable nuclear antigen (ENA) among the general Pakistani population from one of the largest laboratories in Pakistan. Material and methods A total of 1,966 blood samples from a random Pakistani population were included, who were referred by their physicians with suspicion of autoimmune disease. These blood samples were subjected to ANA testing by indirect immunofluorescence method, and subsequently, positive samples were further analyzed for ENA detection in the Section of Chemical Pathology, Department of Pathology at Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Pakistan. An ANA titer of ≥1:80 was taken as positive. ANA was divided into subgroups based on titer: negative, weakly positive (titer of 1:80 or 1:160), moderately positive (titer of 1:320 or 1:640), and strongly positive (titer of ≥1:1280). Further, the frequency of ANA in male and female participants was studied in different age groups (2 to <10, 10 to <20, 20 to <30, 30 to <40, 40 to <50, 50 to <60, 60 to <70, 70 to <80, and 80+ years). Results This study included 1,966 participants, out of which 1,100 (55%) were ANA-positive at a titer of ≥1:80. Out of these ANA positives, the proportion of weakly positive (titer of 1:80 or 1:160), moderately positive (titer of 1:320 or 1:640), and strongly positive (titer of ≥1:1280) were 48.7%, 2.6%, and 4.2%, respectively. The ages ranged from two to 91 years, with a mean age of 43.64 ± 17.4 years. Females (75.5%) showed predominance over males (24.5%) in all age groups, with a ratio of 3:1. The age group in which most ANA positivity was found was 30 to <40 years. Among 1,100 ANA-positive sera, 383 (34.8%) participants tested positive for at least one out of 15 ENA. The most frequent autoantibodies noticed were anti-recombinant Ro52 (Ro52) (19.8%), anti-Sjogren's syndrome type A (SSA) (17.2%), and anti-ribonucleoprotein (RNP) (13.3%). The most prevalent ANA patterns were nuclear homogeneous (27.7%), followed by nuclear speckled (26.5%). Conclusion The frequency of ANA positivity is high in the Pakistani population and differs in different sex and age groups.

Antinuclear Antibody Tests

The presence of antinuclear antibodies (ANAs), which include autoantibodies to extractable nuclear antigens (ENAs), in the sera of patients with connective tissue diseases provides useful immunologic and pathophysiologic insight into the nature of their disease. This article discusses the most commonly used diagnostic modalities for detecting and quantitating the presence of ANA: indirect immunofluorescence assay, enzyme-linked immunosorbent assay, and multiplex bead technology, which serve as useful screening tests. We also review testing for autoantibodies to ENAs, which are often helpful to confirm the diagnosis of a specific connective tissue disease.

Serum Soluble Vascular Cell Adhesion Molecule-1 Overexpression Is a Disease Marker in Patients with First-Time Diagnosed Antinuclear Antibodies: A Prospective, Observational Pilot Study

Objective

Antinuclear antibodies (ANA) serve as screening tests for connective tissue diseases but have low specificity. In this pilot study, we aimed to identify patients with first-time positive ANA and musculoskeletal complaints and correlate serum soluble vascular adhesion molecules as biomarkers.

Methods

Prospective, observational study with 100 ANA-positive patients, comparing them to age- and gender-matched healthy controls (HC, n = 75), was conducted. Serum levels of soluble intercellular adhesion molecule-1 (sICAM-1), endothelial-leukocyte adhesion molecule-1 (sELAM-1), and vascular cell adhesion molecule-1 (sVCAM-1) were measured. A subgroup of patients with systemic sclerosis (SSc) treated with immunosuppressants was followed over 10 months.

Results

Patients belonged to three main entities: rheumatoid arthritis (RA, n = 32), collagen diseases (CD, n = 56) also including systemic sclerosis (SSc, n = 11), and other autoimmune diseases (n = 12). sICAM-1 was similar among groups. sELAM-1 was elevated by 1.9-fold in only in SSc. sVCAM-1 was elevated by 3.1-fold in RA and by 3.3-fold in CD and in other autoimmune diseases by 3.4-fold. Seven SSc patients with immunosuppression had a 2.7-fold increased sVCAM-1 at baseline and reached the levels of healthy controls after 5 months, while CRP, ESR, and clinical parameters remained unchanged.

Conclusion

Our study suggests that sVCAM-1 is a disease marker independent of standard serum parameters in several rheumatic diseases. This study is registered with EU PAS Register number: EUPAS22154.

Anti-nuclear autoantibodies in the general German population: prevalence and lack of association with selected cardiovascular and metabolic disorders-findings of a multicenter population-based study

BACKGROUND

We determined the prevalence of anti-nuclear autoantibodies (ANAs) in the German adult population and examined the association between ANAs and cardiovascular and metabolic disorders.

METHODS

We used data and blood samples from the pretest phases of the German National Cohort, obtained from six of the 18 study centers (n = 1199). All centers applied standardized instruments including face-to-face interviews, anthropometric measurements and collection of blood samples. Self-reported histories of diabetes mellitus, heart attack and elevated blood cholesterol and/or lipids were recorded. Height, weight and blood pressure were measured. ANAs were detected using a semi-automated system (AKLIDES®; Medipan GmbH, Dahlewitz, Germany). A positive ANA was defined as a titer ≥ 1:80. ANA were classified as weakly (1:80 or 1:160), moderately (1:320 or 1:640) or strongly (≥1:1280) positive. Specific autoantibodies against nuclear antigens were detected with second-step assays according to the ANA staining pattern. Associations between the assessed disorders and ANA positivity and pattern were examined using sex and age-adjusted mixed-effects logistic regression models.

RESULTS

Thirty-three percent (95% confidence interval; 31-36%) of the 1196 participants (measurements could not be obtained from three samples) were ANA positive (titer ≥ 1:80). The proportions of weakly, moderately and strongly positive ANA were 29%, 3.3% and 1.3%, respectively. ANA positivity was more common among women than men across all titers (χ², p = 0.03). ANA positivity, even when stratified according to height of titer or immunofluorescent pattern, was not associated with diabetes, elevated blood cholesterol and/or lipids, obesity or hypertension. Second-step autoantibody assays were positive in 41 of the 83 samples (49%) tested, with anti-DFS70 (n = 13) and anti-dsDNA (n = 7) being most frequent. These subgroups were too small to test for associations with the disorders assessed.

CONCLUSIONS

The prevalence of ANA positivity in the German general population was similar to values reported from other countries. Contrary to other studies, there was no association with selected self-reported and objectively measured cardiovascular and metabolic variables.

ANA testing in the presence of acute and chronic infections

Autoantibody testing is performed to help diagnose patients who have clinical symptoms suggestive of possible autoimmune diseases. Antinuclear antibodies (ANA) are present in many systemic autoimmune conditions such as systemic lupus erythematosus (SLE). However, a positive ANA test may also be seen with non-autoimmune inflammatory diseases, including both acute and chronic infections. When the ANA test is used as an initial screen in patients with non-specific clinical symptoms, such as fever, joint pain, myalgias, fatigue, rash, or anemia, the likelihood of a positive result due to infection will increase, especially in children. This article identifies acute and chronic infectious diseases that are likely to produce a positive ANA result and summarizes recent literature addressing both the causes and consequences of these findings.

Inappropriate use of commercial Antinuclear Antibody Testing in a community-based US hospital: a retrospective study

Healthcare providers use antinuclear antibodies (ANAs) to screen and diagnose patients with autoimmune diseases. In the recent years, commercial multiplex ANA kits have emerged as a convenient and fast diagnostic method. Diagnostic testing should follow sequenced algorithms: initial screen followed by specific antibody analysis. Second-level testing as an initial screen for autoimmune disease is inappropriate. We reviewed 68 patients with ANA comprehensive panels over a 6-month period from May 2015 to October 2015. We assessed appropriateness and estimated incurred losses from inappropriate testing. We found 92.6% (63 out of 68) of the ANA comprehensive panel results to be negative. Incurred losses from inappropriate ANA comprehensive panel testing were $66,000. Physicians should become familiar with ANA-sequenced diagnostic algorithms to avoid unnecessary higher level testing.

The concordance of serial ANA tests in an Australian tertiary hospital pathology laboratory

The antinuclear antibody (ANA) tests are some of the more frequently requested tests for the diagnosis of autoimmunity. Although they are used primarily as diagnostic blood tests, multiple requests on the same patient continue to be encountered in the laboratory. This retrospective analysis of serial ANA testing at one pathology laboratory in Australia is the first study that examines the statistical concordance and possible implications of this on clinical practice. High-titred ANA have quite good repeatability for titre and pattern, and low-titred ANA, which can be non-specific, have poor repeatability. Staining patterns are, in general, almost random in nature on serial tests when compared to the first-obtained ANA pattern for each patient. This study confirms that there is little benefit in serial ANA testing, and only if there is a clear change in the patient's clinical picture would repeat of an initial low-titred ANA be useful. The findings reinforce the need for pathology stewardship to minimise costs, wasted resources and unnecessary referrals.

Association between antinuclear antibody titers and connective tissue diseases in a Rheumatology Department

OBJECTIVE

To determine the dilution titles at antinuclear antibodies (ANA) by indirect immunofluorescence observed in cell substrate HEp-2 and its association with the diagnosis of systemic connective tissue disease in ANA test requested by a Rheumatology Unit.

METHOD

Samples of patients attended for the first time in the rheumatology unit, without prior ANA test, between January 2010 and December 2012 were selected. The dilution titers, immunofluorescence patterns and antigen specificity were recorded. In January 2015 the diagnosis of the patients were evaluated and classified in systemic disease connective tissue (systemic lupus erythematosus, Sjögren's syndrome, systemic sclerosis, undifferentiated connective, antiphospholipid syndrome, mixed connective tissue and inflammatory myophaty) or not systemic disease connective tissue.

RESULT

A total of 1282 ANA tests requested by the Rheumatology Unit in subjects without previous study, 293 were positive, predominance of women (81.9%). Patients with systemic connective tissue disease were recorded 105, and 188 without systemic connective tissue disease. For 1/640 dilutions the positive predictive value in the connective was 73.3% compared to 26.6% of non-connective, and for values ≥1/1,280 85% versus 15% respectively. When performing the multivariate analysis we observed a positive association between 1/320 dilution OR 3.069 (95% CI: 1.237-7.614; P=.016), 1/640 OR 12.570 (95% CI: 3.659-43.187; P=.000) and ≥1/1,280 OR 42.136 (95% CI: 8.604-206.345; P=.000).

CONCLUSION

These results show association titles dilution ≥1/320 in ANA's first test requested by a Rheumatology Unit with patients with systemic connective tissue disease. The VPP in these patients was higher than previous studies requested by other medical specialties. This may indicate the importance of application of the test in a targeted way.

Prevalence of antinuclear antibodies in schoolchildren during puberty and possible relationship with musculoskeletal pain: a longitudinal study

OBJECTIVE

The role of antinuclear antibodies (ANA) in children has still to be elucidated. The aim of our study was to evaluate the prevalence and persistence of ANA in schoolchildren during the puberty switch, and the possible relationship with chronic noninflammatory musculoskeletal pain (MSP).

METHODS

Children aged 8-13 years and attending 4 public schools underwent a clinical examination, focusing on pubertal stage and presence of chronic noninflammatory MSP. Laboratory tests to determine the autoantibody-profile were also performed. Subjects with ANA positivity (titer ≥ 1:80) and/or chronic noninflammatory MSP were re-evaluated 3 years later.

RESULTS

Two hundred sixty-one subjects enrolled in the study and 12.3% were ANA-positive, equally distributed in terms of sex and pubertal status. Three years later, in the group of patients studied for chronic noninflammatory MSP (n = 67), ANA positivity significantly increased from 13.4% to 44.8%. In the ANA-positive cohort at baseline (n = 28), 92.9% of subjects were confirmed as being ANA-positive with a significantly increased titer. No association between ANA positivity and chronic noninflammatory MSP was found.

CONCLUSION

ANA prevalence and titers increase during puberty, especially in females, but have no relationship with chronic noninflammatory MSP. This finding may be related to the complex hormonal changes during the puberty switch period and opens new insights into autoimmunity.

Fitting and flailing: recognition of paediatric antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune condition where the presence of antiphospholipid antibodies is thought to predispose to thrombotic events. It is uncommon in the paediatric population, but current diagnostic criteria are based on adult population studies, making assessment of its true paediatric prevalence difficult. We present two cases of paediatric APS, who presented with primary neurological events, and discuss approaches to diagnosis, interpretation of screening investigations, including antinuclear antibodies (ANA), anti-extractable nuclear antigen (ENA) antibodies and lupus anticoagulant. Possible approaches to the management of paediatric APS are discussed.