Antinuclear antibodies: Is the indirect immunofluorescence still the gold standard or should be replaced by solid phase assays?

Prevalence and sociodemographic correlates of antinuclear antibody testing by indirect immunofluorescence or solid-phase assays in a Spanish population: the Camargo Cohort

Autoantibodies are the hallmark of autoimmunity, and specifically, antinuclear antibodies (ANA) are one of the most relevant antibodies present in systemic autoimmune diseases (AID). In the present study, we evaluate the relationship between ANA and sociodemographic and biobehavioral factors in a population with a low pre-test probability for systemic AID. ANA were determined in serum samples at baseline visit from 2997 participants from the Camargo Cohort using indirect immunofluorescence assay, and two solid phase assays (SPA), addressable laser bead immunoassay, and fluorescence enzyme immunoassay. Sociodemographic and biobehavioral features of the subjects were obtained at baseline visit using a structured questionnaire. The prevalence of ANA positive results was significantly higher when indirect immunofluorescence assay was used as screening method in comparison with SPAs, being higher in females, older subjects, and those with higher C-reactive protein levels. Considering biobehavioral features, the prevalence was higher in those individuals with a sedentary lifestyle, and in ex- and non-alcohol users. Moreover, considering the relevance of the antibody load using ANA Screen, the prevalence of the antibody load also increased with age, especially in females. In conclusion, the prevalence of ANA varies depending on sociodemographic and biobehavioral features of the subjects, which could be relevant specifically in a population with a low pre-test probability for systemic AIDs.

Longitudinal analysis of ANA in the Systemic Lupus International Collaborating Clinics (SLICC) Inception Cohort

OBJECTIVES

A perception derived from cross-sectional studies of small systemic lupus erythematosus (SLE) cohorts is that there is a marked discrepancy between antinuclear antibody (ANA) assays, which impacts on clinicians' approach to diagnosis and follow-up. We compared three ANA assays in a longitudinal analysis of a large international incident SLE cohort retested regularly and followed for 5 years.

METHODS

Demographic, clinical and serological data was from 805 SLE patients at enrolment, year 3 and 5. Two HEp-2 indirect immunofluorescence assays (IFA1, IFA2), an ANA ELISA, and SLE-related autoantibodies were performed in one laboratory. Frequencies of positivity, titres or absorbance units (AU), and IFA patterns were compared using McNemar, Wilcoxon and kappa statistics, respectively.

RESULTS

At enrolment, ANA positivity (≥1:80) was 96.1% by IFA1 (median titre 1:1280 (IQR 1:640-1:5120)), 98.3% by IFA2 (1:2560 (IQR 1:640-1:5120)) and 96.6% by ELISA (176.3 AU (IQR 106.4 AU-203.5 AU)). At least one ANA assay was positive for 99.6% of patients at enrolment. At year 5, ANA positivity by IFAs (IFA1 95.2%; IFA2 98.9%) remained high, while there was a decrease in ELISA positivity (91.3%, p<0.001). Overall, there was >91% agreement in ANA positivity at all time points and ≥71% agreement in IFA patterns between IFA1 and IFA2.

CONCLUSION

In recent-onset SLE, three ANA assays demonstrated commutability with a high proportion of positivity and titres or AU. However, over 5 years follow-up, there was modest variation in ANA assay performance. In clinical situations where the SLE diagnosis is being considered, a negative test by either the ELISA or HEp-2 IFA may require reflex testing.

The Past, Present, and Future in Antinuclear Antibodies (ANA)

Autoantibodies are a hallmark of autoimmunity and, specifically, antinuclear antibodies (ANAs) are the most relevant autoantibodies present in systemic autoimmune rheumatic diseases (SARDs). Over the years, different methods from LE cell to HEp-2 indirect immunofluorescence (IIF), solid-phase assays (SPAs), and finally multianalyte technologies have been developed to study ANA-associated SARDs. All of them provide complementary information that is important to provide the most clinically valuable information. The identification of new biomarkers together with multianalyte platforms will help close the so-called "seronegative gap" and to correctly classify and diagnose patients with SARDs. Finally, artificial intelligence and machine learning is an area still to be exploited but in a next future will help to extract patterns within patient data, and exploit these patterns to predict patient outcomes for improved clinical management.

Differentiating between UCTD and early-stage SLE: from definitions to clinical approach

Systemic lupus erythematosus (SLE) is an autoimmune disease with heterogeneous clinical manifestations that can potentially affect every organ and system. SLE is usually identified on the basis of clinical or serological manifestations; however, some individuals can present with signs and symptoms that are consistent with SLE but are not sufficient for a definite diagnosis. Disease in these individuals can either progress over time to definite SLE or remain stable, in which case their disease is often described as intermediate, possible or probable SLE. Alternatively, such individuals might have undifferentiated connective tissue disease (UCTD). Being able to differentiate between those with stable UCTD and those with SLE at an early stage is important to avoid irreversible target-organ damage from occurring. This Review provides insight into existing and evolving perceptions of the early stages of SLE, including clinical and mechanistic considerations, as well as potential paths towards early identification and intervention. Further research into the earliest phases of SLE will be important for the development of targeted diagnostic approaches and biomarkers for the identification of individuals with early disease who are likely to progress to definite SLE.

Assessment of antinuclear antibodies (ANA): National recommendations on behalf of the Croatian society of medical biochemistry and laboratory medicine

Antinuclear antibodies (ANA) represent a family of autoantibodies targeting ubiquitous cellular constituents and are a hallmark of systemic inflammatory autoimmune rheumatic diseases named connective tissue diseases (CTD). The gold standard method for ANA determination is indirect immunofluorescence (IIF) on the human laryngeal epidermoid carcinoma cell line type 2 substrate (HEp-2), but with increasing demand for ANA testing, novel methods eased for automation emerged, which allows testing by staff less experienced in this specific field of laboratory diagnostic. In 2016 The working group (WG) for laboratory diagnostics of autoimmune diseases as part of the Committee for the Scientific Professional Development of the Croatian Society of Medical Biochemistry and Laboratory Medicine (CSMBLM) published the data of a survey regarding general practice in laboratory diagnostics of autoimmune diseases in Croatia. Results indicated high diversity in the performance of autoantibody testing as well as reporting of the results and indicated the need of creating recommendations for the assessment of ANA that would help harmonize diagnostics of systemic autoimmune rheumatic diseases in Croatia. This document encompasses twenty-seven recommendations for ANA testing created concerning indications for ANA testing, preanalytical, analytical, and postanalytical issues, including rational algorithm and quality control assurance. These recommendations are based on the relevant international recommendations and guidelines for the assessment of ANA testing and relevant literature search and should help to harmonize the approach in ANA testing and clarify differences in interpretation of the results obtained using different methods of determination.

Antinuclear Autoantibodies in Health: Autoimmunity Is Not a Synonym of Autoimmune Disease

The incidence of autoimmune diseases is increasing. Antinuclear antibody (ANA) testing is a critical tool for their diagnosis. However, ANA prevalence in healthy persons has increased over the last decades, especially among young people. ANA in health occurs in low concentrations, with a prevalence up to 50% in some populations, which demands a cutoff revision. This review deals with the origin and probable physiological or compensatory function of ANA in health, according to the concept of immunological clearance, theory of autoimmune regulation of cell functions, and the concept of functional autoantibodies. Considering ANA titers ≤1:320 as a serological marker of autoimmune diseases seems inappropriate. The role of anti-DFS70/LEDGFp75 autoantibodies is highlighted as a possible anti-risk biomarker for autoimmune rheumatic disorders. ANA prevalence in health is different in various regions due to several underlying causes discussed in the review, all influencing additive combinations according to the concept of the mosaic of autoimmunity. Not only are titers, but also HEp-2 IFA) staining patterns, such as AC-2, important. Accepting autoantibodies as a kind of bioregulator, not only the upper, but also the lower borders of their normal range should be determined; not only their excess, but also a lack of them or "autoimmunodeficiency" could be the reason for disorders.

Standardization and Quality Assessment Under the Perspective of Automated Computer-Assisted HEp-2 Immunofluorescence Assay Systems

The recent availability of automated computer-assisted diagnosis (CAD) systems for the reading and interpretation of the anti-nuclear antibody (ANA) test performed with the indirect immunofluorescence (IIF) method on HEp-2 cells, has improved the reproducibility of the results and initiated a process of harmonization of this test. Furthermore, CAD systems provide quantitative expression of fluorescence intensity, allowing the introduction of objective quality control procedures to the monitoring of the entire process. The calibration of the reading systems and the automated image interpretation are essential prerequisites for obtaining reproducible and harmonized IIF test results and form the basis for standardization, regardless of the computer algorithms used in the different systems. The use of automated CAD systems, facilitating control procedures, represents a step forward for the quality certification of the laboratory.

Utility of repeated antinuclear antibody tests: a retrospective database study

BACKGROUND

Anti-nuclear antibody (ANA) testing is frequently used as a diagnostic or screening test in patients with inflammatory or musculoskeletal symptoms. The value of repeat testing is unclear. We sought to evaluate the frequency, utility, and cost of repeat ANA testing. The main objective was to assess the positive predictive value of a repeat ANA test for the diagnosis of rheumatological conditions associated with ANA.

METHODS

In this retrospective cohort study, we analysed data from a single, multisite tertiary health network in Australia across a 7-year period. ANA and other autoimmune test results were obtained from the hospital pathology system with a positive ANA titre cutoff set at 1:160. Clinical information was sourced from clinical information systems on any patient who had a change in ANA result from negative to positive on repeat testing. The cost of repeated ANA testing was calculated using the Australian Government Medicare Benefits Schedule.

FINDINGS

From March 19, 2011, to July 23, 2018, a total of 36 715 ANA tests were done in 28 840 patients at a total cost of US$675 029 (2018 equivalent). 14 058 (38·3%) of these ANA tests were positive. 7875 (21·4%) of the ordered tests were repeats in 4887 (16·9%) of the patients, among whom 2683 (54·9%) had initially negative tests, and 2204 (45·1%) had initially positive tests. 511 (19·0%) of the 2683 patients with initially negative tests had a positive result on at least one repeat test, with a median time to first positive result of 1·74 years (IQR 0·54-3·60). A change from negative to positive ANA was associated with a new diagnosis in only five (1·1%) of the 451 patients with clinical information available and no previous diagnosis of an ANA-associated rheumatological condition, yielding a positive predictive value of 1·1% (95% CI 0·4-2·7).

INTERPRETATION

Repeat ANA testing after a negative result has low utility and results in high cost.

FUNDING

Monash Health.

A new diagnostic algorithm for pattern-oriented autoantibody testing according to the ICAP nomenclature: A pilot study

The commercial tests currently available as second-level tests to detect ANA sub-specificities are generally used independently from the ANA immunofluorescence (IIF) pattern. The aim of this study was to evaluate the efficacy of the use of a customizable pattern-oriented antigenic panel by immunoblot (IB) using the International Consensus on ANA Patterns (ICAP) classification scheme, in order to introduce a novel and updated autoimmune diagnostic flowchart. 710 sera referred for routine ANA testing were selected on the basis of the ANA pattern according to the ICAP nomenclature (nuclear speckled AC-2,4,5; nucleolar AC-8,9,10,29; cytoplasmic speckled AC-18,19,20) and on an IIF titer ≥1:320. They were then assayed by three experimental IB assays using a panel of selected antigens. ICAP-oriented IB detected 515 antibody reactivities vs. 457 of traditional anti-ENA in the nuclear speckled pattern group, 108 vs. 28 in the nucleolar pattern group, and 43 vs. 34 in the cytoplasmic speckled pattern. This pilot study may lead the way for a new approach introducing an ICAP pattern-oriented follow up testing as a valid alternative to the existing standard panels, thus enabling more patients with autoimmune rheumatic disease to be accurately diagnosed.

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.

Precision health: A pragmatic approach to understanding and addressing key factors in autoimmune diseases

The past decade has witnessed a significant paradigm shift in the clinical approach to autoimmune diseases, lead primarily by initiatives in precision medicine, precision health and precision public health initiatives. An understanding and pragmatic implementation of these approaches require an understanding of the drivers, gaps and limitations of precision medicine. Gaining the trust of the public and patients is paramount but understanding that technologies such as artificial intelligences and machine learning still require context that can only be provided by human input or what is called augmented machine learning. The role of genomics, the microbiome and proteomics, such as autoantibody testing, requires continuing refinement through research and pragmatic approaches to their use in applied precision medicine.

ANA as an entry criterion for the classification of SLE

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease with highly variable clinical and immunological manifestations. In the classification of patients with this condition, the presence of an antinuclear antibody (ANA) is an important element, with new criteria from the American College of Rheumatology and European League against Rheumatism positioning ANA positivity by an immunofluorescence assay on HEp2-cells (HEp2-IFA) or by an equivalent solid phase assay as the entry criterion. This positioning is based on assumptions about the frequency of ANA positivity in SLE as well as the reliability of the assays. Studies indicate that these assumptions are still a matter of uncertainty since both types of assay show considerable variability and patients with SLE may display negative results in ANA testing. These findings suggest caution in positioning ANA positivity as an entry criterion for classification and point to the value of alternative serological approaches for ANA determinations.

A comparison of a fluorescence enzyme immunoassay versus indirect immunofluorescence for initial screening of connective tissue diseases: Systematic literature review and meta-analysis of diagnostic test accuracy studies

The aim was to compare indirect immunofluorescence (IIF) and fluorescence enzyme immunoassay (FEIA) for initial screening of connective tissue diseases (CTDs) and to evaluate whether combining IIF with FEIA adds value. A comprehensive systematic literature review was conducted to identify fully paired, cross-sectional or case-control studies on ANA screening of CTD reporting results for IIF and FEIA. Study quality was assessed using the QUADAS-2 checklist. The reference standard was assessed against established classification criteria. The meta-analysis used hierarchical, bivariate and mixed-effects models to allow test results to vary within and across studies. Eighteen studies of good to fair quality were included in the review. IIF had a higher sensitivity than FEIA [cut-off 1:160, 7 studies, 3251 patients, 0.83 (95% CI 0.75-0.89) versus 0.73 (95% CI 0.64-0.80); cut-off 1:80, 7 studies, 12,311 patients, 0.89 (95% CI 0.84-0.93) versus 0.78 (95% CI 0.71-0.84)] but lower specificity [1:160, 0.81 (95% CI 0.73-0.87) versus 0.94 (95% CI 0.91-0.95); 1:80, 0.72 (95% CI 0.62-0.81) versus 0.94 (95% CI 0.90-0.96)]. A double-positive test had a higher likelihood ratio (LR) for CTD (26.2 (95% CI 23.0-29.9)) than a single positive test (14.4 (95% CI 13.1-15.9) FEIA+, 5.1 (95% CI 4.8-5.4) IIF+). A double-negative test result had more clinical value for ruling out CTD than a single negative test (LR 0.15 (95% CI 0.12-0.18) versus 0.21 (95% CI 0.18-0.25) IIF; 0.33 (95% CI 0.29-0.37) FEIA-). A FEIA+/IIF- discordant result had a higher LR than an IIF+/FEIA- discordant result (LR 2.4 (95% CI 1.7-3.4) versus 1.4 (95% CI 1.2-1.7)). Because of the comparatively higher specificity of FEIA and higher sensitivity of IIF, the combination of FEIA and IIF increases the diagnostic value. Clinicians should be acquainted with the clinical presentation of CTD and aware of the advantages and disadvantages of FEIA and IIF to avoid misinterpretation.

Clinical relevance of HEp-2 indirect immunofluorescent patterns: the International Consensus on ANA patterns (ICAP) perspective

The indirect immunofluorescence assay (IIFA) on HEp-2 cells is widely used for detection of antinuclear antibodies (ANA). The dichotomous outcome, negative or positive, is integrated in diagnostic and classification criteria for several systemic autoimmune diseases. However, the HEp-2 IIFA test has much more to offer: besides the titre or fluorescence intensity, it also provides fluorescence pattern(s). The latter include the nucleus and the cytoplasm of interphase cells as well as patterns associated with mitotic cells. The International Consensus on ANA Patterns (ICAP) initiative has previously reached consensus on the nomenclature and definitions of HEp-2 IIFA patterns. In the current paper, the ICAP consensus is presented on the clinical relevance of the 29 distinct HEp-2 IIFA patterns. This clinical relevance is primarily defined within the context of the suspected disease and includes recommendations for follow-up testing. The discussion includes how this information may benefit the clinicians in daily practice and how the knowledge can be used to further improve diagnostic and classification criteria.

Harmonizing by reducing inter-run variability: performance evaluation of a quality assurance program for antinuclear antibody detection by indirect immunofluorescence

Background

The introduction of automated anti-nuclear antibody (ANA) indirect immunofluorescence (IIF) analysis may allow for more harmonized ANA IIF reporting, provided that a thorough quality assurance program controls this process. The aim of this study was to evaluate various quality indicators used for ANA IIF analysis with the final goal of optimizing the iQC program.

Methods

In an experimental setup, we introduced artificial errors, mimicking plausible problems during routine practice on a QUANTA-Lyser-NOVA View® system (Inova Diagnostics, San Diego, CA, USA). Predetermined quality indicators were evaluated against predefined acceptance criteria. In addition, we retrospectively investigated the applicability of the selected quality indicators in the daily routine practice during three pre-defined periods.

Results

Both the experimental as the retrospective study revealed that pre-analytical, analytical and post-analytical errors were not highlighted by company internal quality control (iQC) materials. The use of patient derived iQC samples, median fluorescence intensity results per run and the percentage of positive ANA IIF results as additional quality indicators ensured a more adequate ANA IIF quality assurance. Furthermore, negative and moderate positive sample iQC materials merit clinical validation, as titer changes of >1 correspond to clinically important shifts. Traditional Westgard rules, including a clinically defined stop limit, revealed to be useful in monitoring of the supplemental quality indicators.

Conclusions

A thorough ANA IIF quality assurance for daily routine practice necessitates the addition of supplemental quality indicators in combination with well-defined acceptance criteria.

Association of antinuclear antibody status with clinical features and malignancy risk in adult-onset dermatomyositis

BACKGROUND

The clinical significance of antinuclear antibody (ANA) status in adults with dermatomyositis (DM) has yet to be fully defined.

OBJECTIVE

We compared the incidence of amyopathic disease, risk of malignancy, and clinical findings in ANA⁺ and ANA^- patients with adult-onset DM.

METHODS

This was a retrospective cohort study of patients with ANA⁺ or ANA^- adult-onset DM determined by enzyme-linked immunosorbent assay.

RESULTS

Of 231 patients, 140 (61%) were ANA⁺ and 91 (39%) were ANA^-. Compared with the ANA^- patients, the ANA⁺ patients had a lower frequency of dysphagia (15% vs 26% [P = .033]) and heliotrope rash (38% vs 53% [P = .026]). In all, 54 patients (23%) developed malignancy within 3 years of diagnosis of their DM; 11% of the ANA⁺ patients developed malignancy versus 43% of the ANA^- patients (P < .001). There was a strong association between ANA positivity and lower likelihood of malignancy in multivariable analysis (odds ratio, 0.16; P < .001). Conversely, ANA positivity was not associated with amyopathic disease (odds ratio, 0.94; P = .87).

LIMITATIONS

The retrospective nature of the study was a limitation.

CONCLUSION

In patients with adult-onset DM, ANA negativity is associated with increased likelihood of development of malignancy within 3 years of diagnosis of their DM. Particularly close follow-up and frequent malignancy screening may be warranted in ANA^- individuals with DM.

The Utilization of Autoantibodies in Approaches to Precision Health

Precision health (PH) applied to autoimmune disease will need paradigm shifts in the use and application of autoantibodies and other biomarkers. For example, autoantibodies combined with other multi-analyte “omic” profiles will form the basis of disease prediction allowing for earlier intervention linked to disease prevention strategies, as well as earlier, effective and personalized interventions for established disease. As medical intervention moves to disease prediction and a model of “intent to PREVENT,” diagnostics will include an early symptom/risk-based, as opposed to a disease-based approach. Newer diagnostic platforms that utilize emerging megatrends such as deep learning and artificial intelligence and close the gaps in autoantibody diagnostics will benefit from paradigm shifts thereby facilitating the PH agenda.