Detection of antinuclear antibodies: added value of solid phase assay?

Immune-Mediated Necrotizing Myopathy (IMNM): A Story of Antibodies

Immune-mediated necrotizing myopathy (IMNM) is a rare and severe disease that corresponds to a specific entity of idiopathic inflammatory myopathy. Patients with IMNM suffer from proximal muscle weakness, and present high levels of creatine kinase and necrotic myofibers. Anti-Signal Recognition Particle (SRP) and anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase autoantibodies (HMGCR) have recently been identified in two thirds of patients with IMNM and are used as a hallmark of the disease. In this review, we provide a detailed description of these antibodies and the tests used to detect them in the serum of patients. Based on in vitro studies and mouse models of IMNM, we discuss the role of autoantibodies in the pathogenesis of the disease. Finally, in the light of the latest knowledge, we conclude with a review of recent therapeutic approaches in IMNM.

Detection of antinuclear antibodies: recommendations from EFLM, EASI and ICAP

OBJECTIVES

Antinuclear antibodies (ANA) are important for the diagnosis of various autoimmune diseases. ANA are usually detected by indirect immunofluorescence assay (IFA) using HEp-2 cells (HEp-2 IFA). There are many variables influencing HEp-2 IFA results, such as subjective visual reading, serum screening dilution, substrate manufacturing, microscope components and conjugate. Newer developments on ANA testing that offer novel features adopted by some clinical laboratories include automated computer-assisted diagnosis (CAD) systems and solid phase assays (SPA).

METHODS

A group of experts reviewed current literature and established recommendations on methodological aspects of ANA testing. This process was supported by a two round Delphi exercise. International expert groups that participated in this initiative included (i) the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group "Autoimmunity Testing"; (ii) the European Autoimmune Standardization Initiative (EASI); and (iii) the International Consensus on ANA Patterns (ICAP).

RESULTS

In total, 35 recommendations/statements related to (i) ANA testing and reporting by HEp-2 IFA; (ii) HEp-2 IFA methodological aspects including substrate/conjugate selection and the application of CAD systems; (iii) quality assurance; (iv) HEp-2 IFA validation/verification approaches and (v) SPA were formulated. Globally, 95% of all submitted scores in the final Delphi round were above 6 (moderately agree, agree or strongly agree) and 85% above 7 (agree and strongly agree), indicating strong international support for the proposed recommendations.

CONCLUSIONS

These recommendations are an important step to achieve high quality ANA testing.

Concordance between myositis autoantibodies and anti-nuclear antibody patterns in a real-world, Australian cohort

OBJECTIVES

Myositis autoantibodies (MAs) were traditionally used as diagnostic biomarker for idiopathic inflammatory myopathy (IIM). Its clinical utility had recently expanded to include interstitial lung disease (ILD) diagnosis. Depending on the patient cohort, MAs false positives can be common. Correlation between anti-nuclear antibody (ANA) indirect immunofluorescent (IIF) pattern and MAs may improve its positive predictive value (PPV). The aim of our study was to determine the PPV of MAs in IIM and ILD in a real-world patient cohort. We also assessed whether concordance between MAs and ANA IIF pattern can improve the PPV of positive MA results.

METHODS

Patients with positive MAs and corresponding ANA IIF pattern were identified from Sutherland Centre of Immunology, New South Wales Health Pathology, Australia. The corresponding health records were reviewed to identify each patient's primary diagnosis. Chi-square test was used to compare the PPV between MA-ANA concordant and discordant groups.

RESULTS

Between January 2016 and July 2019, 118 patients were positive for at least one MA (mean age 66.7 years, 55% female). The most frequently detected autoantibodies were Ro52, anti-synthetase antibodies, and PM-Scl. The PPV of MAs for IIM or ILD was 47.4%. The overall concordance rate of MAs and ANA IIF pattern was 70.2%. Patients with concordant MA-ANA results were more likely to have true clinical disease (64.1% vs 17.8%, p< 0.001).

CONCLUSION

Myositis autoantibodies have a low PPV for IIM and ILD in a real-world patient cohort. A positive concordance with ANA IIF pattern can improve MA test accuracy.

How to report the antinuclear antibodies (anti-cell antibodies) test on HEp-2 cells: guidelines from the ICAP initiative

Results of the anti-nuclear antibodies-indirect immunofluorescence assay (anti-cell antibodies test) on HEp-2 cell substrates should be communicated to clinicians in a standardized way, adding value to laboratory findings and helping with critical clinical decisions. This paper proposes a test report based on the practices informed by 118 laboratories in 68 countries, with recommendations from the International Consensus on ANA Patterns (ICAP) group. Major focus is placed on the report format containing endpoint titers, immunofluorescence patterns together with anti-cell (AC) nomenclature, remarks on follow-up or reflex testing, and possible other autoantibody associations. ISO 15,189 directives were integrated into the test report. Special situations addressed include serum screening dilutions and endpoint titers, relevance of immunofluorescence patterns with special attention to cytoplasmic patterns, mixed and compound patterns, and how to report different titers corresponding to multiple patterns or autoantibodies in the same sample. This paper suggests a subtitle for the HEp-2-IIFA, namely anti-cell antibodies test, which could gradually substitute the original outdated ANA nomenclature. This ICAP pro forma report represents a further step in harmonizing the way relevant clinical information could be provided by laboratories.

Comparison of the analytical and clinical performances of two different routine testing protocols for antinuclear antibody screening

Background

The diagnosis of systemic autoimmune rheumatic diseases (SARD) is based on the detection of serum antinuclear antibodies (ANA) for which indirect immunofluorescence (IIF) is the golden standard. New solid‐phase immunoassays have been developed to be used alone or in combination with the detection of extractable antinuclear antibodies (ENA) to improve SARD diagnosis. The purpose of this study was to compare the clinical performances of different ANA screening methods alone or in combination with ENA screening methods for SARD diagnosis.

Methods

A total of 323 patients were screened for ANA by IIF, EliA™ CTD Screen, and ELISA methods. Agreements were calculated between the methods. Then, EliA™ CTD Screen positive samples were screened for ENA by line immunoassay (LIA) and fluorescence enzyme immunoassay (FEIA).

Results

The diagnostic accuracy of EliA™ CTD Screen (79% sensitivity and 91% specificity) was better than that of ELISA or IIF. The combination of EliA™ CTD plus IIF had the highest sensitivity (93%). ENA determination revealed that Ro52 and Ro60 were the most prevalent specificities. The use of IIF alone was not able of detecting up to 36% of samples positive for Ro52, and 41% for Ro60.

Conclusions

EliA™ CTD Screen has a better diagnostic performance when compared to IIF and ELISA. The combined use of EliA™ CTD Screen and IIF clearly improves the rate and accuracy of SARD diagnosis. The use of EliA™ CTD Screen as first‐line screening technique allows the detection of antibodies, which could not be detected by IIF alone.

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.

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.

Understanding and interpreting antinuclear antibody tests in systemic rheumatic diseases

Antinuclear antibodies (ANAs) are valuable laboratory markers to screen for and support the diagnosis of various rheumatic diseases (known as ANA-associated rheumatic diseases). The importance of ANA testing has been reinforced by the inclusion of ANA positivity as an entry criterion in the 2019 systemic lupus erythematosus classification criteria. In addition, specific ANAs (such as antibodies to Sm, double-stranded DNA (dsDNA), SSA/Ro60, U1RNP, topoisomerase I, centromere protein B (CENPB), RNA polymerase III and Jo1) are included in classification criteria for other rheumatic diseases. A number of techniques are available for detecting antibodies to a selection of clinically relevant antigens (such as indirect immunofluorescence and solid phase assays). In this Review, we discuss the advantages and limitations of these techniques, as well as the clinical relevance of the differences between the techniques, to provide guidance in understanding and interpreting ANA test results. Such understanding not only necessitates insight into the sensitivity and specificity of each assay, but also into the importance of the disease context and antibody level. We also highlight the value of titre-specific information (such as likelihood ratios).

The clinical relevance of anti-dsDNA antibodies determined by the Elia™ dsDNA assay in patients with negative indirect immunofluorescence on the HEp-2 cell

OBJECTIVES

Data on the clinical importance of the detection of anti-dsDNA antibodies in patients with negative indirect immunofluorescence on the HEp-2 cell (IIF) are sparse and are especially not available for all common commercially available assays. This study aimed to assess the clinical significance of anti-dsDNA antibodies determined by the Elia™ dsDNA assay in patients with negative IIF.

METHODS

We retrospectively examined the medical records of 234 consecutive subjects with detectable anti-dsDNA antibodies determined by the Elia™ dsDNA assay.

RESULTS

A total of 124 subjects with detectable anti-dsDNA autoantibodies were IIF-negative, but yielded positive or borderline results in the Elia™ CTD screen assay for antinuclear antibodies (ANA). Within this group, 6/49 IIF-negative patients (12%) with ANA-associated systemic autoimmune rheumatic disorders (AASARD) and 118/185 subjects (64%) with various other diseases (Non-AASARD) were identified. There was no statistically significant difference with regard to the concentrations of anti-dsDNA antibodies (p=0.53) between the AASARD and the Non-AASARD group. Within the AASARD group, four patients diagnosed with systemic lupus erythematosus (SLE, treated), discoid lupus erythematosus (untreated), indetermined connective tissue disease (untreated) and polymyositis (treated) had positive anti-dsDNA autoantibodies, whereas two patients with treated SLE, thereby one in remission, had borderline concentrations of anti-dsDNA antibodies.

CONCLUSIONS

Our findings suggest that the detection of anti-dsDNA antibodies in IIF-negative patients can be of clinical relevance in some cases. Our results further support the combined use of IIF and solid-phase assays in screening algorithms for ANA, in order to avoid overlooking potentially important autoantibody entities.

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.

Validation of the 2019 ACR/EULAR classification criteria of systemic lupus erythematosus in 100 Japanese patients: a real-world setting analysis

The objective of the study is to evaluate the sensitivity of the new criteria for the classification of systemic lupus erythematosus (SLE), when applied to real SLE cases. We retrospectively reviewed the electronic medical records of 100 consecutive patients who visited St. Luke's International Hospital. Patients were included if they were clinically diagnosed as having SLE and excluded if they had other autoimmune disease or if they were less than 18 years old. Each patient was evaluated if they satisfied the American College of Rheumatology (ACR) 1997 classification criteria (1997 criteria), 2012 Systemic Lupus International Collaborating Clinics criteria (2012 criteria), or 2019 ACR/European League Against Rheumatism (EULAR) criteria. Among the 100 patients, the sensitivity of the 1997, 2012, and 2019 criteria was, 97, 99, and 92%, respectively. The total patient score with the 2019 criteria ranged from 12 to 44 (mean, 27.3). All patients who were classified as non-SLE with the 2019 criteria had an anti-nuclear antibody (ANA) titre of < 1:80. The 2019 criteria for SLE accomplished modestly high sensitivity in the real-world practice, but not as high as the 1997 and 2012 criteria. They possibly misclassify the real SLE cases as non-SLE, especially if patients have a low titre (< 1:80) of ANA.

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.

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.

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.

The clinical significance of borderline results of the Elia CTD Screen assay

Background

Data on the clinical relevance of borderline results of solid-phase assays in the screening for antinuclear antibodies (ANA) are sparse. This study aimed to determine the clinical significance of borderline results of the Elia CTD Screen (ECS; Phadia/Thermo Fisher Scientific, Freiburg, Germany), a fluoroenzymeimmunoassay incorporating 17 recombinant human nuclear antigens.

Methods

We retrospectively examined the medical records of 143 subjects with borderline ECS results for ANA-associated autoimmune disorders (AASARD) and the association with the results of indirect immunofluorescence (IIF) and confirmatory assays for ANA.

Results

AASARD were diagnosed in 10 patients (7%) with systemic lupus erythematosus (n=5; four patients were prediagnosed and in clinical remission), polymyositis overlap syndromes (n=2), scleroderma, Raynaud’s syndrome and undetermined connective tissue disease (each n=1). Most frequently, homogeneous and nucleolar IIF patterns were found. Positive ANA subsets were observed in three patients. Furthermore, four patients were diagnosed with autoimmune liver diseases and yielded positive IIF in three and positive confirmatory assays in all cases. Taken together, 129 subjects had no AASARD. Within this group, 43 patients were IIF positive and most frequently showed speckled, unspecific nucleolar and only rarely homogeneous patterns. Positive ANA subsets were found in low concentrations near to the upper reference range in 18 subjects.

Conclusions

AASARD were observed in 7% of the subjects with borderline ECS and showed homogeneous or nucleolar IIF patterns in the majority of these cases. Our findings suggest that borderline results of the ECS can be clinically relevant and support the concept of a parallel or sequential screening for ANA by both ECS and IIF.

Evaluation of an Automated Screening Assay, Compared to Indirect Immunofluorescence, an Extractable Nuclear Antigen Assay, and a Line Immunoassay in a Large Cohort of Asian Patients with Antinuclear Antibody-Associated Rheumatoid Diseases: A Multicenter Retrospective Study

We assessed the diagnostic utility of the connective tissue disease (CTD) screen as an automated screening test, in comparison with the indirect immunofluorescence (IIF), EliA extractable nuclear antigen (ENA), and line immunoassay (LIA) for patients with antinuclear antibody- (ANA-) associated rheumatoid disease (AARD). A total of 1115 serum samples from two university hospitals were assayed using these four autoantibody-based methods. The AARD group consisted of patients with systemic lupus erythematosus (SLE), systemic sclerosis (SSc), Sjögren's syndrome (SS), and mixed connective tissue disease (MCTD). The qualitative results of all four autoantibody assays showed a significant association with AARDs, compared to controls (P < 0.0001 for all). The areas under the receiver operating characteristic curves (ROC-AUCs) of the CTD screen for differentiating total AARDs, SLE, SSc, SS, and MCTD from controls were 0.89, 0.93, 0.73, 0.93, and 0.95, respectively. The ROC-AUCs of combination testing with LIA were slightly higher in patients with AARDs (0.92) than those of CTD screen alone. Multivariate analysis indicated that all four autoantibody assays could independently predict AARDs. CTD screening alone and in combination with IIF, EliA ENA, and LIA are potentially valuable diagnostic approaches for predicting AARDs. Combining CTD screen with LIA might be effective for AARD patients.

Solid phase assays versus automated indirect immunofluorescence for detection of antinuclear antibodies

Solid phase assays (SPAs) and automated microscope systems are increasingly used to screen for antinuclear antibodies (ANAs). The goal of this study was to evaluate the performance of three automated ANA screening assays; NOVA Lite HEp-2 using NOVA View® (NV, Inova Diagnostics), an automated indirect immunofluorescence method, EliA™ CTD Screen (Fluorescence Enzyme Immunoassay, FEIA; Thermo Fisher) and QUANTA Flash® CTD Screen Plus (Chemiluminescence immunoassay, CIA; Inova Diagnostics). The assays were performed on 480 diagnostic samples from patients with an ANA-associated rheumatic disease (AARD; systemic lupus erythematosus, primary Sjögren's syndrome, systemic sclerosis, inflammatory myopathy, mixed connective tissue disease) and on 767 samples from diseased and healthy controls. Using cut-offs proposed by the manufacturers, the sensitivity was 95%, 80.5% and 86% for NV, FEIA and CIA, respectively. The corresponding specificity was 61% (NV), 97.5% (FEIA) and 88% (CIA). The sensitivity associated with a specificity of ~95% was 79%, 82% and 78% for NV, FEIA, and CIA, respectively. Receiver operating characteristics (ROC) curve analysis revealed no differences in area under the curve (AUC) between the 3 assays when all diseases were grouped. For Sjögren's syndrome, the AUC was higher for SPAs than for NV, whereas for systemic sclerosis, the AUC was higher for NV than for CIA. For all assays, the likelihood ratio for AARD increased with increasing antibody levels and for double positivity of NV with SPA. In conclusion, the performance of automated SPA and IIF was assay- and disease-dependent. Taking into account antibody levels and combining IIF with SPA adds value.

Chronic inflammation predicts long-term mortality in patients with Raynaud's phenomenon

BACKGROUND

Subclinical chronic inflammation could be the driving force behind the recently revealed association between abnormal nailfold capillaries as well as autoantibodies and long-term mortality in patients with incipient Raynaud's phenomenon. Whether laboratory markers that reflect a chronic inflammatory process are directly related to mortality in Raynaud's phenomenon is not known.

METHODS

In total, 2958 patients with incipient Raynaud's phenomenon without previously known connective tissue disease (CTD) were enrolled. At their initial presentation, laboratory tests for C-reactive protein (CRP), leucocytes, fibrinogen and the haemoglobin concentration were obtained. In addition, nailfold capillaries and antinuclear antibodies (ANA) were assessed. Patients' mortality was recorded through a median follow-up period of 9.3 years.

RESULTS

Baseline CRP, fibrinogen and haemoglobin concentration were associated with long-term mortality in an individual analysis of patients with incipient Raynaud's phenomenon. In a multivariable model including patients' age, nailfold capillaries and ANA, a low haemoglobin concentration remained independently related to future mortality. Amongst potential predictors for mortality in patients with Raynaud's phenomenon, a low haemoglobin concentration was most strongly related to patients' mortality risk.

CONCLUSION

In Raynaud's phenomenon, laboratory markers that can be attributed to a chronic inflammatory state independently yield prognostic information in addition to the presence of abnormal nailfold capillaries and ANA. Amongst all prognostic markers, the haemoglobin concentration is most strongly related to patients' mortality in Raynaud's phenomenon.

Analytical and clinical comparison of two fully automated immunoassay systems for the detection of autoantibodies to extractable nuclear antigens

BACKGROUND

Detection of antinuclear antibodies (ANA) by indirect immunofluorescence assay (IIFA) is increasingly substituted by fully automated solid phase immunoassays. This study evaluated the performance of an automated chemiluminescence immunoassay (CIA) and fluorescence enzyme immunoassay (FEIA) and compared their performance to that of IIFA.

METHODS

The study included an unselected prospective study population suspected of systemic autoimmune rheumatic disease. ANA were measured by IIFA, while in parallel sera were tested by CIA QUANTA Flash CTD Screen Plus on the BIO-FLASH® and FEIA EliA CTD Screen on the Phadia® 250 system. As validation, retrospective cohorts of patients with ANA-associated rheumatic disease (AARD) and healthy controls were tested.

RESULTS

Prospectively, sensitivity of IIFA, CIA and FEIA was 90%, 99% and 92%, respectively. Specificity was 76%, 76% and 84%, respectively. Total percent agreements between the three methods were 75.2% (IIFA vs. CIA), 79.2% (IIFA vs. FEIA) and 85.4% (FEIA vs. CIA). The AUC values were 0.95 for CIA and 0.93 for FEIA and did not significantly differ. Retrospectively in individual AARD cohorts, similar results were obtained comparing both CTD screens.

CONCLUSIONS

Both FEIA and CIA CTD screen significantly outperformed IIFA, with a higher specificity for FEIA and higher sensitivity for CIA. Based on ROC analysis, major contributor to the difference between the two solid phase immunoassays was the cut-off.

Current practice in laboratory diagnostics of autoimmune diseases in Croatia. Survey of the Working group for laboratory diagnostics of autoimmune diseases of the Croatian Society of Medical Biochemistry and Laboratory Medicine

INTRODUCTION

With the trend of increasing incidence of autoimmune diseases, laboratories are faced with exponential growth of the requests for tests relating the diagnosis of these diseases. Unfortunately, the lack of laboratory personnel experienced in this specific discipline of laboratory diagnostic, as well as an unawareness of a method limitation often results in confusion for clinicians. The aim was to gain insight into number and type of Croatian laboratories that perform humoral diagnostics with the final goal to improve and harmonize laboratory diagnostics of autoimmune diseases in Croatia.

MATERIALS AND METHODS

In order to get insight into current laboratory practice two questionnaires, consisting of 42 questions in total, were created. Surveys were conducted using SurveyMonkey application and were sent to 88 medical biochemistry laboratories in Croatia for the first survey. Out of 33 laboratories that declared to perform diagnostic from the scope, 19 were selected for the second survey based on the tests they pleaded to perform. The survey comprised questions regarding autoantibody hallmarks of systemic autoimmune diseases while regarding organ-specific autoimmune diseases was limited to diseases of liver, gastrointestinal and nervous system.

RESULTS

Response rate was high with 80 / 88 (91%) laboratories which answered the first questionnaire, and 19 / 19 (1.0) for the second questionnaire. Obtained results of surveys indicate high heterogeneity in the performance of autoantibody testing among laboratories in Croatia.

CONCLUSIONS

Results indicate the need of creating recommendations and algorithms in order to harmonize the approach to laboratory diagnostics of autoimmune diseases in Croatia.

Diagnostic Evaluation of ELISA and Chemiluminescent Assays as Alternative Screening Tests to Indirect Immunofluorescence for the Detection of Antibodies to Cellular Antigens

OBJECTIVES

Detection of antinuclear antibodies (ANAs) plays an important role in the diagnosis of systemic autoimmune rheumatic disease (SARD). Our goal was to evaluate the diagnostic accuracy of three commercially available enzyme-linked immunosorbent assay (ELISA) kits and one chemiluminescent assay for ANA detection, using the clinical diagnostic as the reference standard.

METHODS

We evaluated serum samples from 143 patients with an established diagnosis of SARD (group 1), 166 patients with infectious diseases and other rheumatic diseases for which the ANA test is not useful in diagnosis (group 2), and 89 outpatients with suspicion of SARD (group 3).

RESULTS

The sensitivity for ANA HEp-2, calculated in group 1, was 87.4% and varied between 62.9% and 90.0% for other tests. The specificity for ANA HEp-2, calculated in group 2, was 72.3% and varied between 45.2% and 90.4% for other tests. In group 3, the negative predictive value for ANA Hep-2 was 92.5% and varied between 89.3% and 100% for other tests.

CONCLUSIONS

Some ELISA kits have comparable or superior diagnostic sensitivity to ANA HEp-2 and could be used as an alternative method for ANA screening, therefore allowing the immediate report of the results with fewer false negatives than ANA HEp-2. Owing to the lower specificity, ELISA-positive samples should be submitted to ANA HEp-2 for confirmation of results.

Relation of Nailfold Capillaries and Autoantibodies to Mortality in Patients With Raynaud Phenomenon

BACKGROUND

In incipient Raynaud phenomenon, nailfold capillaroscopy and autoantibody tests are obtained to screen for an emerging connective tissue disease. Whether the presence of abnormal nailfold capillaries and autoantibodies are related to mortality in patients with incipient Raynaud phenomenon is not known.

METHODS AND RESULTS

In 2958 consecutive patients (78% women, median age 45 years) with incipient Raynaud phenomenon without previously known connective tissue disease, nailfold capillaroscopy and laboratory tests for antinuclear antibodies (ANA) and ANA subsets were obtained at initial presentation. During a median follow-up period of 9.3 years, 227 women (9.9% of female patients) and 129 men (20% of male patients) with Raynaud phenomenon died. In comparison with a demographically matched standard population, survival was poorer in patients with Raynaud phenomenon (log-rank test P<0.0001). In patients with Raynaud phenomenon, mortality was higher in men than in women (P<0.0001, Cox proportional hazards model). In women, the presence of abnormal nailfold capillaries, ANA, and anti-Scl-70 antibodies were related to an increase in all-cause mortality. The conjoint presence of abnormal nailfold capillaries and autoantibodies was associated with the highest mortality rates. In men, abnormal nailfold capillaries, and ANA and ANA subsets, as well, were not related to survival. In both sexes, patients' age and serum creatinine were associated with mortality.

CONCLUSIONS

In Raynaud phenomenon, male sex, age, and serum creatinine are related to mortality. Abnormal nailfold capillaries and autoantibodies are associated with an increase in all-cause mortality in female patients, but not in male patients with Raynaud phenomenon.

Clinical performance evaluation of a novel, automated chemiluminescent immunoassay, QUANTA Flash CTD Screen Plus

The QUANTA Flash(®) CTD Screen Plus is a chemiluminescent immunoassay (CIA) for the detection of the major antinuclear antibodies (ANA) on the BIO-FLASH(®) platform. NOVA View(®) is an automated fluorescence microscope that acquires digital images of indirect immunofluorescent assay (IFA) slides. Our goal was to evaluate the clinical performance of the two automated systems and compare their performance to that of traditional IFA. Sera from patients with systemic autoimmune rheumatic diseases (SARD, n = 178), along with disease and healthy controls (n = 204), were tested with the CTD CIA and with NOVA Lite(®) HEp-2 ANA, using both the manual method of reading the IFA slides and the NOVA View instrument. The CTD CIA showed 78.1% sensitivity for SARD, coupled with 94.1% specificity. Manual IFA and NOVA View showed somewhat higher sensitivity (81.5 and 84.8% in SARD, respectively), but significantly lower specificity (79.4 and 64.7%, respectively). Both automated systems displayed somewhat different performance, due to the different principals of ANA detection: IFA with NOVA View digital image interpretation had higher sensitivity, while the CTD CIA showed higher specificity. With the added benefits of full automation, the new CTD CIA is an attractive alternative to traditional ANA screening.

Takotsubo cardiomyopathy and thrombotic thrombocytopenic purpura preceding a lupus diagnosis: a case report

Takotsubo cardiomyopathy, a rare stress-related cardiomyopathy, has been observed in a few cases secondary to systemic lupus erythematosus (SLE). Herein, we report an unusual case where a postmenopausal woman presented initially with Takotsubo syndrome, later developed thrombotic thrombocytopenic purpura and cerebrovascular events, initially without clinical or laboratory features of SLE. During the course of her illness, she was found to satisfy four of the Systemic Lupus International Collaborating Clinics classification criteria for a SLE diagnosis. This unique presentation of our patient, initially with Takotsubo cardiomyopathy, the development of thrombotic thrombocytopenic purpura and cerebrovascular events preceding the diagnosis of SLE illustrates the importance of clinical observation and follow-up.

Comparison of the clinical utility of the Elia CTD Screen to indirect immunofluorescence on Hep-2 cells

We compared the Elia CTD Screen (ECS), a fluoroenzymeimmunoassay incorporating 17 human antinuclear antigens (ANA), with indirect immunofluorescence (IIF) on Hep-2 cells in order to determine the clinical utility of the ECS in additon to or without IIF.

We examined 1708 consecutive serum samples submitted for ANA testing using the ECS and IIF in parallel. Positive screen results were further examined by quantitative fluoroenzymeimmunoassays and/or immunoblots for antibody identification. The medical records were evaluated for systemic rheumatic disorders.

Concordance between ECS and IIF was observed in 1344 (78.8%) samples. ECS had a better detection rate for anti-dsDNA, -SSA/Ro, -SSB/La, -U1RNP and -Jo-1 antibodies, whereas IIF was superior in the detection of anti-CENP-B antibodies as well as anti-histone, -nucleosome and -Pl-12 antibodies, which are not included in the ECS antigen panel. ECS had a 100% sensitivity for Sjögren’s syndrome, systemic sclerosis and Sharp syndrome. The sensitivity for Sjögren’s syndrome was slightly higher for ESC than for IIF (94%). IIF had a higher diagnostic sensitivity for systemic lupus erythematosus, indeterminated connective tissue disease, Raynaud’s syndrome and limited scleroderma, compared to ESC (100% vs. 80%, 100 vs. 75%, 89 vs. 57%, 100 vs. 88.9%).

Our results suggest that the ECS represents an appropriate diagnostic tool for ANA screening. However, since some antigens are not incorporated in the ECS panel, and some ANA can also be missed by IIF, sequential or parallel screening with ECS and IIF may be reasonable when the clinical suspicion for connective tissue disease is high.

Diagnostic utility of unidentified precipitin lines (UPLs) in immune precipitation assays

Unidentified precipitin lines (UPLs) are lines in immune precipitin assays which do not characterise with known extractable nuclear antigen (ENA) antibodies. Currently, the clinical significance of UPLs is uncertain.The aim of this study was to determine the clinical and laboratory correlates of UPLs detected over a 3 year period in a regional immunopathology laboratory.A total of 144 patients with UPLs on ENA testing were retrospectively analysed.ENA by counterimmunoelectrophoresis (CIE) was performed on 11,869 patient samples with further characterisation being performed for 1437 positive results. Ten percent of the positive ENAs demonstrated UPLs. The majority of patients with UPLs were female (71%) with an average age of 60 years. Precipitin lines for both continuously growing myeloid cell line K562 and rabbit thymus extract (RTE) were more frequent (47%), compared to K562 only (41%) or RTE only (12%). The most common antinuclear antibody (ANA) patterns associated with UPLs were speckled (29%), homogenous (16%), mixed patterns (14%), with 30% negative ANA and 5% showing cytoplasmic patterns (Golgi, GWB, mitochondrial). Both ANA positive and ANA negative patients with UPLs were generally associated with connective tissue and autoimmune disease with the majority demonstrating a positive association of UPLs with Ro52 and/or Ro60/SSA detected by Euroimmun line immunoassay. UPLs frequently seen with a negative ANA were also identified in renal disease, pulmonary fibrosis/bronchiectasis and malignancy/lymphoma.UPLs have uncertain diagnostic utility at this stage and further work needs to be done to clarify this question. UPLs were found in systemic and organ specific autoimmune disease, renal, pulmonary and neoplastic disorders. UPLs can occur in both ANA positive and ANA negative sera. The nature of the precipitating antigen in UPLs is still obscure.

Current concepts and future directions for the assessment of autoantibodies to cellular antigens referred to as anti-nuclear antibodies

The detection of autoantibodies that target intracellular antigens, commonly termed anti-nuclear antibodies (ANA), is a serological hallmark in the diagnosis of systemic autoimmune rheumatic diseases (SARD). Different methods are available for detection of ANA and all bearing their own advantages and limitations. Most laboratories use the indirect immunofluorescence (IIF) assay based on HEp-2 cell substrates. Due to the subjectivity of this diagnostic platform, automated digital reading systems have been developed during the last decade. In addition, solid phase immunoassays using well characterized antigens have gained widespread adoption in high throughput laboratories due to their ease of use and open automation. Despite all the advances in the field of ANA detection and its contribution to the diagnosis of SARD, significant challenges persist. This review provides a comprehensive overview of the current status on ANA testing including automated IIF reading systems and solid phase assays and suggests an approach to interpretation of results and discusses meeting the problems of assay standardization and other persistent challenges.

Anti-nuclear antibodies in daily clinical practice: prevalence in primary, secondary, and tertiary care

For the diagnosis of systemic autoimmune rheumatic diseases (SARD), patients are screened for anti-nuclear antibodies (ANA). ANA, as assessed by indirect immunofluorescence (IIF), have a poor specificity. This hampers interpretation of positive results in clinical settings with low pretest probability of SARD. We hypothesized that the utility of positive ANA IIF results increases from primary to tertiary care. We retrospectively determined ANA, anti-ENA, and anti-dsDNA antibody prevalence in patient cohorts from primary (n = 1453), secondary (n = 1621), and tertiary (n = 1168) care settings. Results reveal that from primary care to tertiary care, ANA prevalence increases (6.2, 10.8, and 16.0%, resp.). Moreover, in primary care low titres (70% versus 51% and 52% in secondary and tertiary care, resp.) are more frequent and anti-ENA/dsDNA reactivities are less prevalent (21% versus 39% in secondary care). Typically, in tertiary care the prevalence of anti-ENA/dsDNA reactivities (21%) is lower than expected. From this descriptive study we conclude that positive ANA IIF results are more prone to false interpretation in clinical settings with low pretest probabilities for SARD, as in primary care. Whether alternative approaches, that is, immunoadsorption of anti-DFS70 antibodies or implementation of anti-ENA screen assays, perform better, needs to be determined.