International recommendations for the assessment of autoantibodies to cellular antigens referred to as anti-nuclear antibodies

Performance analysis of automated evaluation of antinuclear antibody indirect immunofluorescent tests in a routine setting

Purpose

Indirect immunofluorescence (IIF) on the human epithelial cell-line HEp-2 (or derivatives) serves as the gold standard in antinuclear antibody (ANA) screening. IIF, and its evaluation, is a labor-intensive method, making ANA testing a major challenge for present clinical laboratories. Nowadays, several automated ANA pattern recognition systems are on the market. In the current study, the EUROPattern Suite is evaluated for its use in daily practice in a routine setting.

Methods

A total of 1033 consecutive routine samples was used to screen for ANA. Results (positive/negative ANA screening, pattern identification and titer) were compared between software-generated results (EUROPattern) and visual interpretation (observer) of automatically acquired digital images.

Results

Considering the visual interpretation as reference, a relative sensitivity of 99.3% and a relative specificity of 88.9% were obtained for negative and positive discrimination by the software (EPa). A good agreement between visual and software-based interpretation was observed with respect to pattern recognition (mean kappa: for 7 patterns: 0.7). Interestingly, EPa software distinguished more patterns per positive sample than the observer (on average 1.5 and 1.2, respectively). Finally, a concordance of 99.3% was observed within the range of 1 titer step difference between EPa and observer.

Conclusions

The ANA IIF results reported by the EPa software are in very good agreement with the results reported by the observer with respect to being negative/positive, pattern recognition and titer, making automated ANA IIF evaluation an objective and time-efficient tool for routine testing.

Electronic supplementary material

The online version of this article (10.1007/s13317-018-0108-y) contains supplementary material, which is available to authorized users.

Different biochemical patterns in type II and type III mixed cryoglobulinemia in HCV positive patients

BACKGROUND

Reversible cryoprecipitability of proteins is observed as a concomitant feature of immune complex formation. Mixed cryoglobulinemia (MC) is systemic vasculitis, associated with mixed IgM and IgG cryoglobulins (CGs) showing rheumatoid factor (RF) activity. It is frequently associated with hepatitis C virus (HCV). This study investigates the presence of IgG RF and anti-nuclear antibodies (ANA) in cryoprecipitates of patients with type III and type II MC, to understand the biochemical patterns associated with different types of MC to a greater degree.

METHODS

Sera from 70 HCV untreated patients with type III or type II MC were tested by immunofixation for IgG3 and through ELISA for IgG RF. Cryoprecipitates were analysed for ANA by indirect immunofluorescence to identify specific patterns.

RESULTS

After stratification according to MC type, the ANA patterns between type II and type III MC were statistically different. IgG3 levels and IgG-RF positivity were significantly higher in type III cryoprecipitate. We observed a higher positivity of IgG3 and a significant difference between the liver fibrosis stage, ANA and IgG-RF in the cryoprecipitate.

CONCLUSION

Results show a combination of biochemical markers and autoantibodies associated to mixed cryoglobulinemia; these findings could be further investigated in order to ascertain their usefulness in assessing the risk for the development of mixed cryoglobulinemia.

Antinuclear antibodies in healthy people and non-rheumatic diseases - diagnostic and clinical implications

The presence of antinuclear antibodies (ANA) is mainly associated with connective tissue diseases (CTD). In addition, their presence is found in healthy people. These antibodies are more common in women and the elderly. Some drugs and xenobiotics are also important for the development of autoimmunity and ANA synthesis. Moreover, the deficiency of vitamin D in the body of patients correlates with occurrence of these antibodies. Unlike the healthy group, a positive ANA count was observed in patients with atopic dermatitis (AD) and in people with immune disorders. Antinuclear antibodies in low counts are also found in the course of chronic bacterial or viral infection and in patients with hematological malignancies. Also the possibility of false positive results, which may be caused by the choice of method used to determine antibodies, should be borne in mind. Taking into account all these factors, it is concluded that the ANA result itself has no diagnostic value.

Detection in whole blood of autoantibodies for the diagnosis of connective tissue diseases in near patient testing condition

A novel technology, photonic ring immunoassay (PRI), for detecting 12 autoantibodies simultaneously in whole blood in less than 15 minutes was evaluated by comparing results from 235 clinically diagnosed patients with standard laboratory tests. The overall agreement was greater than 91% for 10 of the 12 assays, with positive percent agreement greater than 89% for 9 of the assays and negative percent agreement greater than 91% for 10 of them. Thus, the clinical sensitivities and specificities were similar for the 2 methods. In addition, 199 normal blood donors were tested on the ANA 12 PRI, yielding specificities greater than 97.5% for all assays. This proof of concept study shows that this new system is suitable for point of care testing for clinically useful autoantibodies, allowing the doctor to have test results in minutes rather than days.

Antinuclear antibodies detection: A comparative study between automated recognition and conventional visual interpretation

BACKGROUND

The indirect immunofluorescence assay (IIFA) for the detection of antinuclear antibodies (ANA) was firstly described in 1958 and is still considered the reference method for ANA screening. Currently, an automated processing and recognition system for standardized and efficient ANA interpretation by human epithelial (HEp-2) cell-based immunofluorescence (IIF; EUROPattern Suite, Euroimmun) is available in China.

METHODS

In this study, the performance of this novel system for positive/negative classification, pattern recognition (including homogenous, speckled, nucleolar, nuclear dots, cytoplasmic, and centromeres patterns) and titers evaluation was evaluated by comparing to visual interpretation.

RESULTS

Referring to the total of 3681 collected samples, there was an agreement of 98.7% (κ = 0.973) between the visual and automated examination regarding positive/negative discrimination. In sera with single pattern, correct pattern recognition was observed in 94.6% of the samples. The efficiency of automated recognition for single pattern varied for the different patterns. The automatically determined patterns were correct and complete in 1071 of 1620 cases and correct and meaningful but not complete ("main pattern") in another 405 cases, enabling main pattern recognition in 91.1% of all cases. Referring to the titers evaluation, the results within the next titer were considered to be consistent. In 1603 positive sera both by visual and automated evaluation, titers of 1514 sample were consistent, accounting for 94.4%.

CONCLUSION

Attributed to the performance characteristics, EUROPattern system is suitable for clinical use as its high degree of automation and result reliability, and may help clinical laboratories to standardize of IIF evaluation.

Bank1 and NF-kappaB as key regulators in anti-nucleolar antibody development

Systemic autoimmune rheumatic disorders (SARD) represent important causes of morbidity and mortality in humans. The mechanisms triggering autoimmune responses are complex and involve a network of genetic factors. Mercury-induced autoimmunity (HgIA) in mice is an established model to study the mechanisms of the development of antinuclear antibodies (ANA), which is a hallmark in the diagnosis of SARD. A.SW mice with HgIA show a significantly higher titer of antinucleolar antibodies (ANoA) than the B10.S mice, although both share the same MHC class II (H-2). We applied a genome-wide association study (GWAS) to their Hg-exposed F2 offspring to investigate the non-MHC genes involved in the development of ANoA. Quantitative trait locus (QTL) analysis showed a peak logarithm of odds ratio (LOD) score of 3.05 on chromosome 3. Microsatellites were used for haplotyping, and fine mapping was conducted with next generation sequencing. The candidate genes Bank1 (B-cell scaffold protein with ankyrin repeats 1) and Nfkb1 (nuclear factor kappa B subunit 1) were identified by additional QTL analysis. Expression of the Bank1 and Nfkb1 genes and their downstream target genes involved in the intracellular pathway (Tlr9, Il6, Tnf) was investigated in mercury-exposed A.SW and B10.S mice by real-time PCR. Bank1 showed significantly lower gene expression in the A.SW strain after Hg-exposure, whereas the B10.S strain showed no significant difference. Nfkb1, Tlr9, Il6 and Tnf had significantly higher gene expression in the A.SW strain after Hg-exposure, while the B10.S strain showed no difference. This study supports the roles of Bank1 (produced mainly in B-cells) and Nfkb1 (produced in most immune cells) as key regulators of ANoA development in HgIA.

High Frequency of Extractable Nuclear Autoantibodies in Wheat-Related Disorders

Background and aims:

There has been broad interest to explore the presence of autoimmunity among wheat-sensitive individuals, but neither the pathogenesis nor the relevance has been established. In this study, we evaluated the frequencies and levels of autoantibodies, which are important biomarkers of autoimmunity, in subjects with wheat-related disorders and controls. Anti-nuclear antibodies (ANA) and the specific ones against extractable nuclear antigens (ENA) were investigated.

Methods:

A total of 713 subjects who showed symptoms related to wheat ingestion were addressed to Vibrant America Clinical Laboratory from December 2015 to November 2017. Serum samples were collected from all subjects and tested with a wheat protein antibody panel (IgG and IgA to 18 proteins at the peptide level) and an autoantibody panel (ANA by immunofluorescence analysis and 10 ENA antibodies). Retrospective analysis was completed using de-identified clinical data and test results.

Results:

In the retrospective analysis, 38 (5%) were seropositive in a Celiac Disease panel, 491 (83%) were seropositive in a wheat protein antibody panel “Wheat Zoomer,” and 84 (12%) were seronegative in both panels. Anti-nuclear antibodies were detected in similar portions of the celiac disease subjects (13%), the Wheat Zoomer–positive subjects (12%), and seronegative controls (15%), which is also very close to the reported occurrence of ANA positivity (15%) in the healthy population. The prevalence of anti-ENA was reported to be less than 2% in the general population; however, our study found it to be much higher in the celiac disease subjects (29%) and the wheat-sensitive subjects (27%), compared with a smaller proportion of seronegative controls (19%). The prevalence of anti-histone was especially prominent among the celiac disease subjects (73%) and the Wheat Zoomer–positive subjects (60%).

Conclusions:

High proportions of wheat-related disease subjects carry ENA antibodies that are important specific biomarkers of autoimmunity.

Autoimmune antibodies and asbestos exposure: Evidence from Wittenoom, Western Australia

BACKGROUND

Studies comparing different forms of asbestos are rare, and limited by the failure to compare results with unexposed populations. We compare autoimmune responses among former workers and residents of the crocidolite mining and milling town of Wittenoom, Western Australia, with an unexposed population.

METHODS

ANA testing using indirect immunofluorescence was performed on randomly selected serum samples from Wittenoom workers or residents and compared with those from participants of another unexposed cohort study.

RESULTS

ANA scores were higher in the Wittenoom participants compared with Busselton and the odds of being ANA positive was fivefold greater among Wittenoom participants than Busselton (OR 5.5, 95%CI 2.3-13.0).

CONCLUSIONS

This study is the first to report increased ANA positivity among persons exposed exclusively to crocidolite. This finding of a high frequency of positive ANA tests among crocidolite-exposed subjects may be an indicator for an increased risk of systemic autoimmune diseases and needs further scrutiny.

The importance of detecting anti-DFS70 in routine clinical practice: comparison of different care settings

Background:

Screening for antinuclear antibodies by indirect immunofluorescence (ANA-IIF) is essential in the diagnostic workup of ANA-associated autoimmune rheumatic diseases (AARDs). However, also healthy individuals may test positive, making the interpretation challenging. Recent reports suggest that dense fine speckled 70 antibodies (anti-DFS70) may facilitate this challenge. Here, we investigate their clinical importance based on data from four Belgian laboratories (one primary, two secondary and one tertiary care).

Methods:

At least one specific DFS70 assay (DFS70 IgG ELISA or lineblot [Euroimmun, full length antigen] and/or DFS70 IgG CLIA [Inova Diagnostics, truncated antigen]) was performed on four consecutive cohorts of homogeneous-like ANA-IIF samples (n=697). Co-occurrence with AARD-specific ANA and clinical information were documented in the anti-DFS70-positive samples.

Results:

Using a combination of solid phase techniques, we found between 7.6% and 26% anti-DFS70 in the different cohorts. Focusing on anti-DFS70 CLIA-positive samples without co-occurrence of AARD-specific ANA, we observed a trend towards lower frequency in tertiary (8% [p=0.0786]) and secondary care (12% [p=0.1275] and 6% [p<0.001]) compared to primary care (21%). Moreover, in this specific subpopulation, AARD was less frequent (0%–50% compared to 6%–77% in the total anti-DFS70-positive group).

Conclusions:

Anti-DFS70 prevalence depends on the applied assay and care setting. Our data suggest that, for an ANA-IIF-positive patient, it is rather the absence of AARD-associated ANA and clinical symptoms that contribute to the exclusion of AARD than the presence of anti-DFS70. Nevertheless, isolated anti-DFS70 helps to clarify positive ANA-IIF results, especially if pretest probability for AARD is low.

Assay variation in the detection of antinuclear antibodies in the sera of patients with established SLE

OBJECTIVE

The expression of antinuclear antibodies (ANA) is considered almost constant in systemic lupus erythematosus (SLE), although recent experience has suggested that many subjects with SLE considered for clinical trials are ANA negative at screening. The objective of this study is to determine whether assay variation can influence ANA detection in patients with established SLE.

METHODS

Sera from 103 patients with established SLE were tested using three different immunofluorescence assays (IFA) for ANA determination. ANA determinations were also performed by an ELISA and bead-based multiplex assay.

RESULTS

With IFA kits, the frequency of ANA negativity varied from 5 to 23 of 103 samples (4.9%-22.3%). The ELISA and multiplex assays showed that 12 (11.7%) and 14 (13.6%) samples were negative, respectively. Samples positive in all assays differed from those with discordant assay results in the frequency of historical anti-double-stranded DNA positivity and low complement levels at the time of blood sampling.

DISCUSSION

These findings indicate that ANA negativity occurs in patients with established SLE although the frequency varies depending on the assay kit. Given the range of negativity with well-validated assays, these findings raise questions about whether ANA positivity should be employed to determine eligibility for clinical trials.

International consensus on antinuclear antibody patterns: definition of the AC-29 pattern associated with antibodies to DNA topoisomerase I

The indirect immunofluorescence assay (IFA) on HEp-2 cells is the reference method for autoantibody screening. The HEp-2 IFA pattern provides useful information on the possible autoantibodies in the sample. The International Consensus on Antinuclear Antibody Patterns (ICAP) initiative seeks to define and harmonize the nomenclature of HEp-2 IFA patterns. The most relevant and usual patterns have been assigned an alphanumeric code from anti-cell (AC)-1 to AC-28 and were organized into a classification algorithm (www.ANApatterns.org). The systemic sclerosis-associated autoantibodies to DNA topoisomerase I (Topo I) produce a peculiar composite 5-element HEp-2 IFA pattern (Topo I-like pattern) comprising the staining of the nucleus, metaphase chromatin plate, nucleolar organizing region, cytoplasm and nucleolus. In a recent assessment of the European Consensus Finding Study Group on autoantibodies, a well-defined anti-Topo I sample was blindly analyzed and classified according to ICAP AC patterns by 43 participant laboratories across Europe. There were wide variations among these laboratories in reporting nuclear, nucleolar and cytoplasmic patterns, indicating the inadequacy of the existing AC patterns to report the Topo I-like pattern. Several ICAP member laboratories independently demonstrated the overall consistency of the HEp-2 IFA Topo I-like pattern using HEp-2 slides from different manufacturers. The ICAP committee reviewed 24 candidate images and selected the four most representative images to be available on the ICAP website. The proper recognition of the AC-29 pattern should trigger suspicion of the presence of anti-Topo I antibodies, which may engender appropriate analyte-specific reflex tests to confirm the autoantibody specificity.

Automated Processing and Evaluation of Anti-Nuclear Antibody Indirect Immunofluorescence Testing

Indirect immunofluorescence (IIF) is considered by the American College of Rheumatology (ACR) and the international consensus on ANA patterns (ICAP) the gold standard for the screening of anti-nuclear antibodies (ANA). As conventional IIF is labor intensive, time-consuming, subjective, and poorly standardized, there have been ongoing efforts to improve the standardization of reagents and to develop automated platforms for assay incubation, microscopy, and evaluation. In this study, the workflow and performance characteristics of a fully automated ANA IIF system (Sprinter XL, EUROPattern Suite, IFA 40: HEp-20-10 cells) were compared to a manual approach using visual microscopy with a filter device for single-well titration and to technologist reading. The Sprinter/EUROPattern system enabled the processing of large daily workload cohorts in less than 8 h and the reduction of labor hands-on time by more than 4 h. Regarding the discrimination of positive from negative samples, the overall agreement of the EUROPattern software with technologist reading was higher (95.6%) than when compared to the current method (89.4%). Moreover, the software was consistent with technologist reading in 80.6–97.5% of patterns and 71.0–93.8% of titers. In conclusion, the Sprinter/EUROPattern system provides substantial labor savings and good concordance with technologist ANA IIF microscopy, thus increasing standardization, laboratory efficiency, and removing subjectivity.

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.

Recognition and Relevance of Anti-DFS70 Autoantibodies in Routine Antinuclear Autoantibodies Testing at a Community Hospital

Antinuclear autoantibodies (ANA) displaying a dense fine speckled pattern (DFS, ICAP AC-2) on HEp-2 cells are frequently observed in clinical laboratory referrals, often associated with anti-DFS70 specificity. Anti-DFS70 positive patients rarely develop systemic autoimmune rheumatic disease (SARD), especially in the absence of clinical evidence or additional anti-extractable nuclear antigen (ENA) antibodies, prompting suggestions that an isolated DFS70-specific ENA may be an exclusionary finding for SARD. In this study, the frequency and diagnostic significance of anti-DFS70 autoantibodies was investigated in a community hospital cohort of patients undergoing routine ANA testing. ANA screening was performed by HEp-20-10-based indirect immunofluorescence, followed by ENA profiling using a multiparametric line immunoassay (LIA). Of 6,511 patient samples tested for ANA in 2016, the DFS pattern was identified in 1,758 (27.0%), 720 (41.0%) of which were anti-DFS70 positive by LIA. Of these, 526 (73.1%) revealed isolated anti-DFS70 reactivity, while 194 (26.9%) showed additional ENA specificities. Among 1,038 anti-DFS70 negative or borderline samples, 778 (75.0%) were ENA profile negative, while the remaining 260 (25.0%) showed a varied presence of other ENA specificities. Chart reviews of patients with an isolated anti-DFS70 ANA affirmed that ANA-related SARD is rare in the absence of clinical evidence or other ENA specificities, there being no case thus far identified. Rheumatoid arthritis patients occasionally had an isolated anti-DFS70 ANA and were positive for rheumatoid factor and anti-cyclic citrullinated peptide antibodies. In conclusion, the recognition of a DFS ANA pattern using a mitotic-rich HEp-2 substrate, followed by confirmation of anti-DFS70 specificity should be a routine ANA testing service. Use of an expanded ENA profile and clinical correlation is necessary to affirm the "isolation" of anti-DFS70 as the cause of an ANA. Recognition of isolated anti-DFS70 ANA enables reassurance of patients that SARD is unlikely, thus avoiding referral for more extensive testing. The presence of significant elevations of other ENAs may reflect SARD and warrants close clinical correlation and follow-up.

Analytical variability in the determination of anti-double-stranded DNA antibodies: the strong need of a better definition of the old and new tests

Anti-dsDNA antibodies are a heterogeneous group of antibodies, quite specific for SLE. Their variability is related to the assay used, the immunoglobulin class secondary antibody, and the dsDNA source. The standardization of measuring anti-dsDNA antibodies is still poor and different methods yield different results. Several novel technologies were developed during the last decades that represent viable alternatives to the traditional methods such as the chemiluminescent immunoassay (CIA) and multiplex flow immunoassay (MFI). Additionally, positive results for anti-dsDNA antibodies can be detected in patients with inflammatory arthritis (IA) treated with different biologics reducing its clinical specificity for SLE. Anti-dsDNA antibody levels were evaluated in 246 patient samples: 70 SLE and 176 disease control (including 96 IA during treatment with different biologics), using three enzyme immunoassays (indirect enzyme immunoassay, Bio-Rad Laboratories; chemiluminescent immunoassay, Inova Diagnostics; multiplex flow immunoassay, Bio-Rad Laboratories) and three Crithidia luciliae immunofluorescence tests (CLIFT) (Euroimmun AG, Bio-Rad Laboratories, INOVA Diagnostics). Diagnostic performances were assessed both including and excluding the IA patients. Agreements, measured by the Cohen's Kappa between all methods, ranged from moderate to substantial (0.47-0.68). The clinical sensitivities for the anti-dsDNA antibody tests varied from 5.7% by CLIFT A up to 33.3% provided by EIA while the clinical specificities varied from 89.8% by MFI to 98.9% provided by CLIFT B and C. Newer technologies, such as MFI and CIA, showed great potential as a diagnostic application. Significant variations among anti-dsDNA antibody assays were observed confirming the lack of standardization.

Antiphosphatidylserine/prothrombin (aPS/PT) antibodies are associated with Raynaud phenomenon and migraine in primary thrombotic antiphospholipid syndrome

Objectives

Antibodies to phosphatidylserine/prothrombin complex (aPS/PT) detectable in sera of some patients with antiphospholipid syndrome (APS) have been shown to correlate with thrombosis. However, associations of aPS/PT antibodies with APS related disorders remain unclear.

Aim

To evaluate whether there are any associations between aPS/PT antibodies and Raynaud phenomenon, migraine and/or valvular lesions in primary thrombotic APS (PAPS).

Methods

We enrolled 67 consecutive patients (56 women) with thrombotic PAPS (VTE in 80.6%), aged 46.2 ± 13.5 years. The exclusion criteria were: acute coronary syndromes or stroke within preceding 6 months, cancer, severe comorbidities and pregnancy. The IgG and IgM aPS/PT antibodies were determined by ELISA with the cut-off of 30 units. We recorded Raynaud phenomenon, migraine and valvular lesions.

Results

Positive IgM or/and IgG aPS/PT antibodies were observed in 29 patients (43.3%), with a higher prevalence of IgM antibodies ( n = 27, 40.3%) compared with IgG isotype ( n = 12, 17.9%, p = 0.014). aPS/PT antibodies were observed most commonly in patients with triple aPL ( n = 12, 85.7%) compared with those with double ( n = 5, 35.7%) or single aPL antibodies (n = 12, 30.8%, p = 0.03), with no association with demographics, the ANA titre, the type of thrombotic events or medications. Raynaud phenomenon, migraine and valvular lesions were observed in 15% ( n = 10), 30% ( n = 20) and 18% ( n = 12) of the patients, respectively. Raynaud phenomenon and migraine, but not valvular lesions, were markedly more frequent in PAPS patients presenting with positive aPS/PT antibodies ( n = 10, 34.5% vs. n = 0, 0%; p = 0.0001).

Conclusions

In PAPS patients aPS/PT antibodies are related to the occurrence of both Raynaud phenomenon and migraine.

Challenges in the Standardization of Autoantibody Testing: a Comprehensive Review

Standardization and harmonization are complementary tools to achieve higher testing quality in laboratory medicine. Both are of great relevance and are strongly needed in autoimmune diagnostics, due to the impressive advance in basic research and technological development observed in this diagnostic field in recent years that has led to the introduction of many new tests and new analytical methods. It is, therefore, essential that this strong innovative thrust is translated into clinical practice in a coordinated way to avoid confusion and the risk of potentially harmful errors for the patient. However, while standardization of antibody assays is a very complex task, harmonization of procedures and behaviors is a more feasible target and should necessarily include all the phases of the total testing process-in the pre-analytical phase, appropriateness of test requests, harmonization of autoantibody terminology, and adoption of uniform nomenclature for laboratory tests; in the analytical phase, harmonization of measurements, and sharing of test profiles and diagnostic algorithms; and in the post-analytical phase, harmonization of data reporting, and criteria for interpreting immunoserological results, especially harmonization of units, reference intervals, decision limits, and definition and notification of critical values. We here provide and discuss some examples of harmonization initiatives related to anti-nuclear antibodies, TSH receptor, and anti-thyroid peroxidase antibodies and to antibodies associated with autoimmune hepatitis and with celiac disease. These initiatives could be the starting steps to achieve a wider consensus and a closer interaction among stakeholders in the path of autoimmune diagnostics harmonization to enhance clinical effectiveness and provide greater patient safety.

Diagnostic utility of automated indirect immunofluorescence compared to manual indirect immunofluorescence for anti-nuclear antibodies in patients with systemic rheumatic diseases: A systematic review and meta-analysis

OBJECTIVE

This study aimed to review and compare the analytical and clinical performance of automated indirect immunofluorescence (AIIF) and manual indirect immunofluorescence (MIIF) as anti-nuclear antibody screening assays for patients with systemic rheumatic diseases (SRDs), such as systemic lupus erythematosus (SLE) and systemic sclerosis (SSc).

METHODS

A systematic literature search was performed in the Medline, Embase, Cochrane, Web of Science, and Scopus databases for studies published before August 2017. A bivariate random effects model was used to calculate the summary diagnostic values.

RESULTS

Twenty-two studies involving 6913 positive and 1818 negative samples of MIIF, as well as 524 combined SRD, 132 SLE, and 104 SSc patients, and 520 controls were available for meta-analysis. The summary positive concordance (PC) of qualitative result between AIIF and MIIF was 93.7%, whereas PCs of total pattern (68.5%; homogeneous, 52.3%; speckled, 56.5%; nucleolar, 52.7%; centromere, 51.4%; nuclear dot, 11.7%) and titer (77.8%) exhibited significantly lower values. The summary clinical sensitivities of AIIF vs. MIIF were 84.7% vs 78.2% for combined SRDs, 95.5% vs. 93.9% for SLE, and 86.5% vs. 83.7% for SSc, respectively. Meanwhile, the summary specificities of AIIF vs. MIIF were 75.6% vs. 79.6% for combined SRDs, 74.2% vs. 83.3% for SLE, and 74.2% vs. 83.3% for SSc, respectively. Although the differences in sensitivity and specificity between AIIF and MIIF were not significant in most subgroups, the summary specificity of SLE and SSc showed statistically significant changes.

CONCLUSIONS

Our systematic meta-analysis demonstrates that AIIF is comparable to MIIF in distinguishing between the positive and negative results, and screening SRDs based on clinical sensitivities and standardization. However, improvements in the pattern and titer recognition and clinical specificities are necessary.

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.

Bench to bedside review of myositis autoantibodies

Idiopathic inflammatory myopathies represent a heterogeneous group of autoimmune diseases with systemic involvement. Even though numerous specific autoantibodies have been recognized, they have not been included, with the only exception of anti-Jo-1, into the 2017 Classification Criteria, thus perpetuating a clinical-serologic gap. The lack of homogeneous grouping based on the antibody profile deeply impacts the diagnostic approach, therapeutic choices and prognostic stratification of these patients. This review is intended to highlight the comprehensive scenario regarding myositis-related autoantibodies, from the molecular characterization and biological significance to target antigens, from the detection tools, with a special focus on immunofluorescence patterns on HEp-2 cells, to their relative prevalence and ethnic diversity, from the clinical presentation to prognosis. If, on the one hand, a notable body of literature is present, on the other data are fragmented, retrospectively based and collected from small case series, so that they do not sufficiently support the decision-making process (i.e. therapeutic approach) into the clinics.

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.

Performance of Antinuclear Antibodies for Classifying Systemic Lupus Erythematosus: A Systematic Literature Review and Meta-Regression of Diagnostic Data

OBJECTIVE

To review the published literature on the performance of indirect immunofluorescence (IIF)-HEp-2 antinuclear antibody (ANA) testing for classification of systemic lupus erythematosus (SLE).

METHODS

A systematic literature search was conducted in the Medline, Embase, and Cochrane databases for articles published between January 1990 and October 2015. The research question was structured according to Population, Intervention, Comparator, Outcome (PICO) format rules, and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations were followed where appropriate. Meta-regression analysis for diagnostic tests was performed, using the ANA titer as independent variable, while sensitivity and specificity were dependent variables.

RESULTS

Of 4,483 publications screened, 62 matched the eligibility criteria, and another 2 articles were identified through reference analysis. The included studies comprised 13,080 SLE patients in total, of whom 12,542 (95.9%) were reported to be IIF-ANA positive at various titers. For ANA at titers of 1:40, 1:80, 1:160, and 1:320, meta-regression gave sensitivity values of 98.4% (95% confidence interval [95% CI] 97.6-99.0%), 97.8% (95% CI 96.8-98.5%), 95.8% (95% CI 94.1-97.1%), and 86.0% (95% CI 77.0-91.9%), respectively. The corresponding specificities were 66.9% (95% CI 57.8-74.9%), 74.7% (95% CI 66.7-81.3%), 86.2% (95% CI 80.4-90.5%), and 96.6% (95% CI 93.9-98.1%), respectively.

CONCLUSION

The results of this systematic literature review and meta-regression confirm that IIF-ANAs have high sensitivity for SLE. ANAs at a titer of 1:80 have sufficiently high sensitivity to be considered as an entry criterion for SLE classification criteria, i.e., formally test other classification criteria for SLE only if ANAs of at least 1:80 have been found.

Serology in autoimmune hepatitis: A clinical-practice approach

Serology is key to the diagnosis of autoimmune hepatitis (AIH). Clinicians need to be aware of which tests to request, how to interpret the laboratory reports, and be familiar with the laboratory methodology. If correctly tested, >95% of AIH patients show some serological reactivity. Indirect immunofluorescence on triple rodent tissue is recommended as first screening step, since it allows the detection of all liver-relevant autoantibodies, except for anti-soluble liver antigen (SLA) antibody, which needs to be detected by molecular based assays. The threshold of immunofluorescence positivity is a titer equal or exceeding 1/40, but for patients younger than 18years even lower titers are clinically significant. Anti-nuclear antibody (ANA) and/or anti-smooth muscle (SMA) antibody characterize type 1 AIH. ANA in AIH typically shows a homogeneous staining pattern on HEp2 cells, without any specific target antigen. Anti-SMA displays different staining patterns on indirect immunofluorescence: the vascular/glomerular (VG) and the vascular/glomerular/tubular (VGT) patterns are considered specific for AIH, whilst the V pattern can be found in a variety of diseases. Type 2 AIH, which is rare and affects mostly children/adolescents, is characterized by anti-liver kidney microsomal 1 and/or anti-liver cytosol 1 antibodies. The presence of anti-neutrophil cytoplasmic antibody (ANCA), particularly atypical p-ANCA (pANNA), points to the diagnosis of AIH, especially in absence of other autoantibodies. Since it is associated with sclerosing cholangitis and inflammatory bowel disease, these conditions have to be ruled out. The only antibody specific for AIH is anti-SLA, which is associated with a more severe disease course.

Autoimmune liver disease-related autoantibodies in patients with biliary atresia

AIM

To investigate the prevalence and clinical significance of autoimmune liver disease (ALD)-related autoantibodies in patients with biliary atresia (BA).

METHODS

Sera of 124 BA patients and 140 age-matched non-BA controls were assayed for detection of the following autoantibodies: ALD profile and specific anti-nuclear antibodies (ANAs), by line-blot assay; ANA and anti-neutrophil cytoplasmic antibody (ANCA), by indirect immunofluorescence assay; specific ANCAs and anti-M2-3E, by enzyme linked immunosorbent assay. Associations of these autoantibodies with the clinical features of BA (i.e., cytomegalovirus infection, degree of liver fibrosis, and short-term prognosis of Kasai procedure) were evaluated by Spearman’s correlation coefficient.

RESULTS

The overall positive rate of serum autoantibodies in preoperative BA patients was 56.5%. ALD profile assay showed that the positive reaction to primary biliary cholangitis-related autoantibodies in BA patients was higher than that to autoimmune hepatitis-related autoantibodies. Among these autoantibodies, anti-BPO was detected more frequently in the BA patients than in the controls (14.8% vs 2.2%, P < 0.05). Accordingly, 32 (25.8%) of the 124 BA patients also showed a high positive reaction for anti-M2-3E. By comparison, the controls had a remarkably lower frequency of anti-M2-3E (P < 0.05), with 6/92 (8.6%) of patients with other liver diseases and 2/48 (4.2%) of healthy controls. The prevalence of ANA in BA patients was 11.3%, which was higher than that in disease controls (3.3%, P < 0.05), but the reactivity to specific ANAs was only 8.2%. The prevalence of ANCAs (ANCA or specific ANCAs) in BA patients was also remarkably higher than that in the healthy controls (37.9% vs 6.3%, P < 0.05), but showed no difference from that in patients with other cholestasis. ANCA positivity was closely associated with the occurrence of postoperative cholangitis (r = 0.61, P < 0.05), whereas none of the autoantibodies showed a correlation to cytomegalovirus infection or the stages of liver fibrosis.

CONCLUSION

High prevalence of autoantibodies in the BA developmental process strongly reveals the autoimmune-mediated pathogenesis. Serological ANCA positivity may be a useful predictive biomarker of postoperative cholangitis.

Simultaneous Distinction of Monospecific and Mixed DFS70 Patterns During ANA Screening with a Novel HEp-2 ELITE/DFS70 Knockout Substrate

Systemic autoimmune connective tissue disorders are characterized by circulating antinuclear antibodies (ANA). Although there are several technologies available for ANA screening, indirect immunofluorescence (IIF) using Human epithelial cells-2 (HEp-2) substrate remains the primary and recommended method because of its superior sensitivity. HEp-2 substrates can detect a multitude of patterns resulting from autoantibody binding to various protein and nucleic acid autoantigens distributed throughout the nucleus and cytoplasm of the cells. The great diversity of monospecific and mixed patterns resulting from positive reactions on HEp-2 substrate also complicate the interpretation and accuracy of reporting. One specific example which received utmost attention recently is the dense fine speckled 70 (DFS70) pattern resulting from autoantibodies that specifically bind to a protein called lens epithelium derived growth factor (LEDGF). Lack of clear association with a specific systemic autoimmune disease and high prevalence in healthy populations have made accurate interpretation of DFS70 pattern important. Accurate distinction of DFS70 pattern from disease-associated patterns using conventional HEp-2 substrate is challenging. Moreover, frequent co-occurrence of DFS70 pattern along with disease-associated patterns such as homogeneous, speckled, and mixed homogeneous-speckled patterns complicate the IIF interpretation. The goal of this paper is to demonstrate the utility of a novel engineered HEp-2 IIF substrate that retains all advantages of conventional HEp-2 substrate while simultaneously providing the ability to distinguish DFS70 pattern with high confidence in both monospecific and mixed ANA positive examples. The new substrate is further able to unmask disease-associated ANA patterns previously concealed by DFS70 pattern.

Autoimmune comorbidity in achalasia patients

BACKGROUND AND AIM

Idiopathic achalasia is a rare esophageal motor disorder. The disease state manifests local and systemic inflammation, and it appears that an autoimmune component and specific autoantibodies participate in the pathogenesis. The study aims to determine the prevalence of autoimmune and chronic inflammatory diseases in patients with achalasia and compare the results with those from patients with gastroesophageal reflux disease (GERD).

METHODS

It was a cross-sectional and included 114 patients with idiopathic achalasia and 114 age-matched and sex-matched control patients with GERD. Data on the presence of autoimmune and inflammatory diseases, the time of presentation, and any family history of autoimmune disease were obtained from the hospital's medical records.

RESULTS

Seventy three (64%) were female patients (mean age: 42.3 ± 15.5; median disease duration: 12 months). We identified the presence of autoimmune disease in 19 patients with achalasia (16.7%), hypothyroidism was the main diagnosis, and it was present in 52.6% of patients compared with 4.2% in controls. Thirteen of the 19 achalasia patients (68.4%) with autoimmune disease had history of familial autoimmunity. We identified 11 achalasia (9.6%) and 5 GERD patients (4.16%) with an inflammatory condition. Compared with the GERD, the achalasia group was 3.8 times more likely to have an autoimmune disease (95% CI: 1.47-9.83), 3.0 times more likely to have thyroidopathies (95% CI: 1.00-9.03), and 3.02 times more likely to suffer from any chronic inflammatory disease (95% CI: 1.65-6.20).

CONCLUSIONS

The non-negligible number of patients with autoimmune diseases identified among the patients with idiopathic achalasia supports the hypothesis that achalasia has an autoimmune component.

Recent Approaches To Optimize Laboratory Assessment of Antinuclear Antibodies

The presence of antinuclear antibodies (ANAs) is a hallmark of a number of systemic autoimmune rheumatic diseases, and testing is usually performed as part of the initial diagnostic workup when suspicion of an underlying autoimmune disorder is high. The indirect immunofluorescence antibody (IFA) technique is the preferred method for detecting ANAs, as it demonstrates binding to specific intracellular structures within the cells, resulting in a number of staining patterns that are usually categorized based on the cellular components recognized and the degree of binding, as reflected by the fluorescence intensity or titer. As a screening tool, the ANA patterns can guide confirmatory testing useful in elucidating a specific clinical diagnosis or prognosis. However, routine use of ANA IFA testing as a global screening test is hampered by its labor-intensiveness, subjectivity, and limited diagnostic specificity, among other factors. This review focuses on current efforts to standardize the nomenclature of ANA patterns and on alternative methods for ANA determination, as well as on recent advances in image-based computer algorithms to automate IFA testing in clinical laboratories.

Performance analysis of automated evaluation of Crithidia luciliae-based indirect immunofluorescence tests in a routine setting - strengths and weaknesses

BACKGROUND

Antibodies directed against dsDNA are a highly specific diagnostic marker for the presence of systemic lupus erythematosus and of particular importance in its diagnosis. To assess anti-dsDNA antibodies, the Crithidia luciliae-based indirect immunofluorescence test (CLIFT) is one of the assays considered to be the best choice. To overcome the drawback of subjective result interpretation that inheres indirect immunofluorescence assays in general, automated systems have been introduced into the market during the last years. Among these systems is the EUROPattern Suite, an advanced automated fluorescence microscope equipped with different software packages, capable of automated pattern interpretation and result suggestion for ANA, ANCA and CLIFT analysis.

METHODS

We analyzed the performance of the EUROPattern Suite with its automated fluorescence interpretation for CLIFT in a routine setting, reflecting the everyday life of a diagnostic laboratory. Three hundred and twelve consecutive samples were collected, sent to the Central Diagnostic Laboratory of the Maastricht University Medical Centre with a request for anti-dsDNA analysis over a period of 7 months.

RESULTS

Agreement between EUROPattern assay analysis and the visual read was 93.3%. Sensitivity and specificity were 94.1% and 93.2%, respectively. The EUROPattern Suite performed reliably and greatly supported result interpretation.

CONCLUSIONS

Automated image acquisition is readily performed and automated image classification gives a reliable recommendation for assay evaluation to the operator. The EUROPattern Suite optimizes workflow and contributes to standardization between different operators or laboratories.

EASI – European Autoimmunity Standardisation Initiative: facing the challenges of diagnostics in autoimmunity

The European Autoimmunity Standardisation Initiative (EASI) has been founded in order to improve autoimmune diagnostics by stimulating the interaction between the clinicians and laboratory specialists, by standardization of autoantibody tests, and by harmonization of testing algorithms. The ultimate goal of EASI is to utilize autoimmune diagnostics in the best way in order to optimize patient care. This mini-review gives an overview of the historical perspective of EASI and summarizes the major achievements.

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.

ANA Testing: What should we know about the methods, indication and interpretation?

Though ANA is a common test requested in several settings, one may not be aware of the potential traps for interpretation. Nowadays, there is a trend for autoantibodies diagnostics to move from traditional time honored manual methods to high throughput automated platforms. Nevertheless, the clinical significance and assay performance characteristics may be different from those “historical” methods. Though indirect immunofluorescence is the gold standard method for ANA tests, different laboratories vary in the slides (from different cell lines and commercial source, e.g., Hep 2, Hep 2000, etc.), screening dilutions, terminology, reporting format and expertise. Hence, discrepancy in results among different laboratories is not uncommon and could be confusing. Knowing the assay characteristic and limitations helps proper results interpretation and facilitate patient’s management. Indeed, the titer and pattern by indirect immunofluorescence do provide valuable information in screening patients. In particular, DFS pattern with the associated anti-DFS70 antibodies has been shown to have a role to risk stratify cases referred for suspected autoimmune rheumatic disease.

[Management of systemic lupus erythematosus]

In the last few decades a number of small, often largely unrecognized steps have fundamentally changed the management of systemic lupus erythematosus (SLE). The current goal is to stop all disease activity without long-term use of more than 5 mg prednisolone per day. Remission, i.e. absence of activity in the SLE activity score of choice, is the defined target in the treat to target approach. The essential basic measures include life-long hydroxychloroquine as well as protection from sunlight (UV) and vitamin D substitution. Patients suffering from SLE need more vaccinations than the healthy population and control of risk factors for atherosclerosis is critical for long-term survival. Methotrexate is on par with azathioprine. If disease activity cannot be controlled in this way, belimumab is an approved therapeutic option. Cyclophosphamide is still used but only in life-threatening situations, such as lupus nephritis or central nervous system (CNS) vasculitis and in drastically reduced doses. Alternatively, off-label mycophenolate mofetil (MMF) can be used particularly for lupus nephritis and off-label rituximab in refractory disease courses. Numerous novel approaches are being tested in controlled trials and it is hoped that new drugs will be available for SLE patients within a few years.

Next-Generation Autoantibody Testing by Combination of Screening and Confirmation-the CytoBead® Technology

Occurrence of autoantibodies (autoAbs) is a hallmark of autoimmune diseases, and the analysis thereof is an essential part in the diagnosis of organ-specific autoimmune and systemic autoimmune rheumatic diseases (SARD), especially connective tissue diseases (CTDs). Due to the appearance of autoAb profiles in SARD patients and the complexity of the corresponding serological diagnosis, different diagnostic strategies have been suggested for appropriate autoAb testing. Thus, evolving assay techniques and the continuous discovery of novel autoantigens have greatly influenced the development of these strategies. Antinuclear antibody (ANA) analysis by indirect immunofluorescence (IIF) on tissue and later cellular substrates was one of the first tests introduced into clinical routine and is still an indispensable tool for CTD serology. Thus, screening for ANA by IIF is recommended to be followed by confirmatory testing of positive findings employing different assay techniques. Given the continuous growth in the demand for autoAb testing, IIF has been challenged as the standard method for ANA and other autoAb analyses due to lacking automation, standardization, modern data management, and human bias in IIF pattern interpretation. To address these limitations of autoAb testing, the CytoBead® technique has been introduced recently which enables automated interpretation of cell-based IIF and quantitative autoAb multiplexing by addressable microbead immunoassays in one reaction environment. Thus, autoAb screening and confirmatory testing can be combined for the first time. The present review discusses the history of autoAb assay techniques in this context and gives an overview and outlook of the recent progress in emerging technologies.

Detection of autoantibodies to 3-hydroxy-3-methylglutaryl-coenzyme a reductase by ELISA in a reference laboratory setting

BACKGROUND

We investigated the performance of an ELISA for the detection of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) IgG antibodies in immune-mediated necrotizing myopathies (IMNM).

METHODS

Patients positive for HMGCR antibodies (n=61) or negative (n=78) by protein immunoprecipitation (IP), and healthy controls (n=100) were used to evaluate the ELISA. Unique consecutive serum samples (n=155) received at ARUP Laboratories for HMGCR IgG testing by ELISA were also investigated and analysed for serum muscle enzymes (aldolase, creatine kinase, and myoglobin). The ELISA's sensitivity, specificity, and percentage agreement were assessed relative to IP. Correlation between specific muscle enzyme concentration and the presence of HMGCR antibody was determined.

RESULTS

Overall agreement between ELISA and IP was 93.4%. Using the IP as reference, the sensitivity and specificity of the ELISA was 95.1%, and 100%, respectively. Inter- and intra-assay coefficient of variation of the ELISA was <10.0%, and ≤15.0%, respectively. In the consecutive cohort, 21 (13.6%) samples tested positive for HMGCR IgG. Concentrations of aldolase, creatine kinase, and myoglobin were significantly higher (all p<0.0001) in patients positive for HMGCR antibodies at the time of evaluation.

CONCLUSIONS

We confirm significant reliability of HMGCR antibodies as measured by the ELISA for the evaluation of IMNM.

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.