Utility of Antinuclear Antibody Screening by Various Methods in a Clinical Laboratory Patient Cohort

Historical Perspective on Antinuclear Antibody Testing

Serum factors binding to cell nuclei were first described in the 1940s, and the antibodies responsible for the binding to self (autoantibodies) were discovered in the late 1950s. Routine standardized testing using a cell line (HEp-2) started in the 1980s and continues to evolve. In addition to the classic immunofluorescence assay (IFA), various immunochemical techniques have been developed for the measurement of antinuclear antibodies (ANAs). The complexity of ANA IFA pattern reading and the varying sensitivities, specificities, and overall clinical performance of the alternative methods have often generated controversies and sometimes even confusion among healthcare providers and laboratorians. A better understanding of the historical roots of ANA testing can aid in understanding these controversies and assist with selecting the best-performing methods. In this review, we present historic and contemporary ANA testing methods, highlighting the pros and cons of each. We also provide an overview of the current practice of ANA testing based on several recent large laboratory surveys. For optimal patient care, it is critical that clinicians and laboratorians using ANA testing understand the performance and limitations of the methods used by their institutions, as well as the meaning of the test results. Recently published surveys and standardization efforts initiated by several stakeholder scientific organizations will likely lead to new ANA diagnostic guidelines, to be followed by an improvement in testing practices, management, and outcomes for patients with autoimmune disorders.

Antinuclear Antibodies in Non-Rheumatic Diseases

Antinuclear antibodies (ANAs) are critical immunological markers commonly associated with various connective tissue diseases (CTDs). However, these autoantibodies are also detectable in healthy individuals, patients with non-rheumatic autoimmune diseases, those with viral infections, and subjects using specific medications (such as procainamide, hydralazine, and minocycline) that can lead to drug-induced ANA elevation. The standard method for ANA detection is indirect immunofluorescence, a process that requires precision and thoroughness as it assesses both titer and fluorescence patterns. Additionally, immunoblotting and enzyme-linked immunosorbent assay (ELISA) are recommended to identify specific ANAs precisely, highlighting the importance of precision in ANA detection. This review explores the advantages and limitations of current ANA detection methods. It also describes the clinical implications of ANA presence in non-rheumatic diseases, including autoimmune disorders, infectious conditions, non-autoimmune and non-infectious diseases, and autoimmune cutaneous diseases. The presence of elevated ANA titers in these contexts can complicate clinical decision-making, as the diagnostic value of ANA testing alone is limited in non-rheumatic conditions. However, despite these limitations, ANA remains a key component in diagnosing and prognosis systemic CTDs, as it can indicate disease activity, severity, and response to treatment, which is of utmost importance in rheumatology and internal medicine. This paper provides a comprehensive review of the role of ANA in non-rheumatic diseases. It focuses on ANA diagnostic and prognostic significance and offers valuable insights for clinical practice.

Autoantibodies in Common Connective Tissue Diseases: A Primer for Laboratory Professionals

Background

Autoimmune connective tissue disorders are a significant health concern throughout the world with an estimated prevalence of 3% to 5%. They are associated with a variety of autoantibodies that play roles in their diagnosis, risk stratification, prognostication, and/or management. While some autoantibodies have been well-characterized for use in clinical laboratories, many more are in the research stage. Rapid transition from research to clinical practice, lack of clinical guidelines, and harmonization across a rapidly growing number of commercially available tests create numerous challenges to clinicians and laboratories.

Content

This article briefly discusses common connective tissue disorders and their association with well-known autoantibodies, describes current methods used in clinical laboratories, and outlines their advantages and limitations in the context of these diseases.

Summary

Understanding the role of specific autoantibodies and various methodologies for autoantibody testing are important for laboratory professionals who may be introducing/repatriating new tests, updating existing tests, or advising clinicians/patients about testing options/results. Collaboration between laboratory professional staff and clinicians, around the advantages and limitations of each methodology, is also important in their appropriate clinical utilization.

Correlation of ANA Characteristics with pANCA IFA Interference

BACKGROUND

Antineutrophil cytoplasmic antibody (ANCA) testing by the indirect immunofluorescence assay (IFA) is important for the diagnosis of autoimmune vasculitis. A common analytical interference for ANCA-IFA is the presence of an antinuclear antibody (ANA), which can cause an apparent perinuclear ANCA (pANCA) result on ethanol-fixed neutrophils. Here, the association of ANA patterns, titers, and concentrations with pANCA interference is investigated.

METHODS

Samples positive for ANA by IFA with homogeneous, speckled, dense fine speckled (DFS), and centromere patterns were tested for ANA by enzyme immunoassay (EIA)] and for ANCA by IFA on ethanol-fixed neutrophils. Titers and concentrations were determined for the ANA-IFA and EIA, respectively, and correlated with the frequency of pANCA interpretations.

RESULTS

For ANA-EIA positive samples (≥1.1U), 20.0% led to a pANCA interpretation compared to 5.1% for negative samples (≤1.0U). For samples positive by ANA-IFA, 12.9% resulted in a pANCA interpretation. Interference on pANCA correlated with ANA-IFA titer, with ANA titers ≥1:1280 identified as pANCA positive in 20.9% of samples compared to 9.7% for titers <1:1280. There was also a correlation with ANA pattern, as homogeneous samples were most likely to be called positive for pANCA (31.7%), followed by speckled (8.8%), DFS (6.8%), and centromere (3.6%).

CONCLUSIONS

Positivity for ANA by EIA is associated with increased prevalence of pANCA interpretation. Samples positive for ANA by IFA also demonstrated this association, particularly with higher-titer, homogeneous patterns. Laboratories can use this information to determine an optimal workflow for when investigating potential pANCA interferences.

Antinuclear antibodies in neurology and their clinical application

Antinuclear antibodies (ANA) are a diverse group of autoantibodies found in various systemic autoimmune disorders. They represent a key diagnostic marker in the diagnosis of connective tissue disorders (CTD). Although many techniques exist, ANA by Indirect Immunofluorescence (IIF) remains the gold standard for diagnosing CTDs. Neurologists should be aware of the type of assay used for detection and the advantages and disadvantages of using each method. Through this article, we aimed to review the methodological aspects of the detection of ANA and its subtypes and their clinical relevance in various neurologic disorders.

Comparison study of bead-based and line-blot multiplex ANA immunoassays in the diagnosis of systemic autoimmune rheumatic diseases

OBJECTIVES

Detection of antinuclear antibodies (ANA) by immunofluorescence assay (IFA) is increasingly substituted by multiplex bead-based immunoassay (MBA) and line-blot immunoassay (LIA). This study is to compare the diagnostic performance of MBA and LIA ANA assays on clinically characterized patient samples.

METHODS

A total of 728 serum samples from 385 patients with systemic autoimmune rheumatic diseases (SARD), 204 patients with non-SARD diseases, and 139 apparently healthy subjects were tested with the BioPlex 2200 ANA Screen and EuroLine ANA Profile 3 as the representative MBA and LIA technologies and HEp-2 ANA IFA. Clinical data were collected independent of laboratory analysis and later related to the ANA test results. The clinical diagnostic performances were analyzed using Analyse-it software.

RESULTS

The MBA demonstrated higher area under curve (AUC) compared to LIA (0.814 vs 0.761, p = 0.002) and HEp-2 IFA (0.814 vs 0.771, p = 0.008). The MBA and LIA ANA methods showed higher specificity (83.8% and 77.0% vs 67.6%, p < 0.001 and p = 0.005) but lower sensitivity (79.0% and 75.3% vs 86.5%, p < 0.001) compared to HEp-2 IFA. The MBA and LIA ANA revealed substantial to excellent agreements on specific antinuclear antibodies except anti-dsDNA, with the total agreement from 92.3 to 99.9% and Cohen's kappa from 0.71 to 0.98. The MBA demonstrated significantly higher sensitivity (58.1% vs 19.8%, p < 0.001) and comparable specificity (95.9% vs 97.5%, p = 0.221) on anti-dsDNA assay for the diagnosis of SLE compared to LIA.

CONCLUSIONS

The MBA and LIA ANA assays have higher specificity but lower sensitivity compared to HEp-2 IFA. There are good agreements between MBA and LIA ANA for the specific antinuclear antibodies except for anti-dsDNA. The MBA ANA demonstrated better assay performance compared to LIA as the MBA possesses higher sensitivity and specificity in the diagnosis of SARD. Key Points • The multiplex bead-based immunoassay (MBA) ANA outperformed line-blot immunoassay (LIA) and traditional HEp-2 IFA. • There are good agreements between the MBA BioPlex 2200 ANA Screen and LIA EuroLine ANA Profile 3 for the most of specific antinuclear antibodies except anti-dsDNA. • Additional anti-dsDNA testing is suggested when EuroLine ANA Profile 3 is used for the aid of SLE diagnosis and management. • The positive predictive value of both multiplex ANA assays can be substantially increased without significantly affecting negative predictive value by using at least two specific antinuclear antibodies for reporting a positive ANA result.

New insights into the role of antinuclear antibodies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by antinuclear antibodies (ANAs) that form immune complexes that mediate pathogenesis by tissue deposition or cytokine induction. Some ANAs bind DNA or associated nucleosome proteins, whereas other ANAs bind protein components of complexes of RNA and RNA-binding proteins (RBPs). Levels of anti-DNA antibodies can fluctuate widely, unlike those of anti-RBP antibodies, which tend to be stable. Because anti-DNA antibody levels can reflect disease activity, repeat testing is common; by contrast, a single anti-RBP antibody determination is thought to suffice for clinical purposes. Experience from clinical trials of novel therapies has provided a new perspective on ANA expression during disease, as many patients with SLE are ANA negative at screening despite previously testing positive. Because trial results suggest that patients who are ANA negative might not respond to certain agents, screening strategies now involve ANA and anti-DNA antibody testing to identify patients with so-called 'active, autoantibody-positive SLE'. Evidence suggests that ANA responses can decrease over time because of the natural history of disease or the effects of therapy. Together, these findings suggest that, during established disease, more regular serological testing could illuminate changes relevant to pathogenesis and disease status.

A hierarchical bivariate meta-analysis of diagnostic test accuracy to provide direct comparisons of immunoassays vs. indirect immunofluorescence for initial screening of connective tissue diseases

OBJECTIVES

To compare indirect immunofluorescence (IIF) for antinuclear antibodies (ANA) against immunoassays (IAs) as an initial screening test for connective tissue diseases (CTDs).

METHODS

A systematic literature review identified cross-sectional or case-control studies reporting test accuracy data for IIF and enzyme-linked immunosorbent assays (ELISA), fluorescence enzyme immunoassay (FEIA), chemiluminescent immunoassay (CLIA) or multiplex immunoassay (MIA). The meta-analysis used hierarchical, bivariate, mixed-effect models with random-effects by test.

RESULTS

Direct comparisons of IIF with ELISA showed that both tests had good sensitivity (five studies, 2321 patients: ELISA: 90.3% [95% confidence interval (CI): 80.5%, 95.5%] vs. IIF at a cut-off of 1:80: 86.8% [95% CI: 81.8%, 90.6%]; p = 0.4) but low specificity, with considerable variance across assays (ELISA: 56.9% [95% CI: 40.9%, 71.5%] vs. IIF 1:80: 68.0% [95% CI: 39.5%, 87.4%]; p = 0.5). FEIA sensitivity was lower than IIF sensitivity (1:80: p = 0.005; 1:160: p = 0.051); however, FEIA specificity was higher (seven studies, n = 12,311, FEIA 93.6% [95% CI: 89.9%, 96.0%] vs. IIF 1:80 72.4% [95% CI: 62.2%, 80.7%]; p < 0.001; seven studies, n = 3251, FEIA 93.5% [95% CI: 91.1%, 95.3%] vs. IIF 1:160 81.1% [95% CI: 73.4%, 86.9%]; p < 0.0001). CLIA sensitivity was similar to IIF (1:80) with higher specificity (four studies, n = 1981: sensitivity 85.9% [95% CI: 64.7%, 95.3%]; p = 0.86; specificity 86.1% [95% CI: 78.3%, 91.4%]). More data are needed to make firm inferences for CLIA vs. IIF given the wide prediction region. There were too few studies for the meta-analysis of MIA vs. IIF (MIA sensitivity range 73.7%-86%; specificity 53%-91%).

CONCLUSIONS

FEIA and CLIA have good specificity compared to IIF. A positive FEIA or CLIA test is useful to support the diagnosis of a CTD. A negative IIF test is useful to exclude a CTD.

Screening for connective tissue disease-associated antibodies by automated immunoassay

BACKGROUND

Antinuclear antibodies (ANAs) are useful for the diagnosis of ANA-associated systemic rheumatic disease (AASRD). The objective of this study was the evaluation of an immunoassay that detects antibodies to a mixture of 17 antigens as an alternative to indirect immunofluorescence (IIF).

METHODS

Nine thousand eight hundred and fifty-six consecutive patients tested for ANAs were tested by IIF and EliA connective tissue disease screen (Thermo-Fisher). Medical records were reviewed for 2475 patients, including all patients that tested positive/equivocal by either test and a selection of 500 patients that tested negative.

RESULTS

Concordance between IIF and EliA was 83.1%. AASRD was found in 12.8% of IIF-positive patients, 30.2% of EliA-positive patients and 0.4%, 46.6%, 5.8% and 3.0% of patients that tested, respectively, double negative, double positive, single positive for EliA and single positive for IIF. The association with AASRD increased with increasing antibody level. IIF and EliA were positive in, respectively, 90.4% and 69.9% of systemic lupus erythematosus (n=83), 100% and 84.1% of systemic sclerosis (n=63), 86.7% and 93.3% of Sjögren's syndrome (n=45), 88.2% and 52.9% of polymyositis/dermatomyositis (n=17), and in all cases of mixed connective tissue disease (n=8). The specificity was projected to be 94%-96% for EliA and 86% for IIF. When all AASRDs were taken together, the areas under the curve of receiver operator curves were similar between IIF and EliA.

CONCLUSIONS

The positive predictive value for AASRD was higher for EliA than for IIF, but, depending on the disease, EliA might fail to detect antibodies that are detected by IIF. Combining immunoassay with IIF adds value.

Quality Monitoring Approach for Optimizing Antinuclear Antibody Screening Cutoffs and Testing Work Flow

BACKGROUND

An antinuclear antibody (ANA) testing strategy involving enzyme immunoassay (EIA) screening that reflexed to immunofluorescence assay (IFA) was implemented, monitored, and optimized for clinical utility.

METHODS

The clinical utility, test performance, and workload implications of various ANA testing strategies were compared during the following study phases: (a) Preimplementation (n = 469) when IFA was used for all ANA screening, (b) Verification (n = 58) when EIA performance was confirmed, (c) Implementation (n = 433) when a reflexive strategy (EIA screen/IFA confirmation) was implemented, and (d) Postimplementation (n = 528) after the reflexive strategy was optimized. Sequential samples were captured in the Preimplementation, Implementation, and Postimplementation phases for clinical performance evaluation.

RESULTS

Clinical performance of the EIA screen, per ROC analysis yielded area under the curve (AUC) of 0.846 in the Implementation phase and increased to 0.934 Postimplementation (P < 0.01); AUC for IFA similarly increased, from 0.678 to 0.808 (P = 0.05). The reflexive testing strategy increased screening sensitivity from 61% Preimplementation (IFA) to 98% (EIA) at Implementation and was maintained after optimization (98%, Postimplementation). Optimization decreased the false-positive rates for both EIA (from 40% to 18%) and IFA (18% to 8%) and was associated with reductions in daily full-time equivalent (by 33%) and IFA slide use (by 50%).

CONCLUSIONS

Continuous quality monitoring approaches that incorporate sequential data sets can be used to evaluate, deploy, and optimize sensitive EIA-based ANA screening methods that can reduce manual IFA work without sacrificing clinically utility.