QUANTA Flash Research Articles

B-072 Analytical Evaluation of a Novel Fully Automated Multiplexed Microarray Immunoassay for the Simultaneous Detection of Eleven Autoantibodies Associated with Connective Tissue Diseases in a Spanish Reference Laboratory

Abstract Background Detection of different autoantibodies is key in the identification of autoimmune diseases; however, most available devices are either individual tests and/or manual/semi-automated. Development of fully-automated multiplexed devices for autoantibody testing is needed. We evaluated the analytical performance of the novel MosaiQ® AiPlex CTD (AiPlex-CTD) microarray, used with the fully-automated MosaiQ system, for simultaneous qualitative detection of eleven autoantibodies associated with connective tissue diseases (CTD), compared with selected CE-marked devices. Methods AiPlex-CTD microarrays (AliveDx, Switzerland) were prepared by printing antigens onto functionalized glass chips. Microarrays consisting of 2 separate sides (1 side was printed, leaving the other side available for future addition of antigens) were assembled into magazines (containing 250 microarrays) for processing on the MosaiQ 125 instrument. Serum samples from a Spanish refence laboratory, characterized as reactive to ≥1 autoantibodies using Quanta Flash® CTD Screen (Werfen, Spain) or as non-reactive by FIDISTM Connective Profile (Theradiag, France). All samples were tested with AiPlex-CTD. Positive percent agreement (PPA) and negative percent agreement (NPA), overall and for individual analytes were calculated. Results Compared with Quanta Flash® CTD Screen, AiPlex-CTD showed PPA ranging from 80% for Sm to 100% for SS-A 60, TRIM21, U1RNP, Jo-1 and Scl-70. No reactive samples were available for Sm/RNP and Ribosomal P. Compared with FIDIS, NPA ranged from 95% for dsDNA, Scl-70 and CENP-B and 100% for SS-A 60, TRIM21, SS-B, Sm, Sm/RNP, U1RNP, Jo-1 and Ribosomal P. Performance details for individual analytes are shown in the Table. Conclusions In this sample cohort, AiPlex-CTD demonstrated high concordance with the compared CE-marked devices for the automated qualitative detection of the autoantibodies included in the assay, which is line with previous observations in a larger cohort using FIDIS and other CE-marked devices. This high throughput multiplexed platform has the potential to help optimize CTD testing by simplifying complex testing pathways.

B-073 Analytical Performance of a Novel, Fully Automated Multiplexed Microarray Immunoassay Prototype for the Simultaneous Detection of Fifteen Autoantibodies Associated with Connective Tissue Diseases

Abstract Background There is currently a limited offer of automated multi-analyte tests for autoantibody testing in autoimmune connective tissue diseases (CTD). We assessed the analytical performance of a novel, single-use, multiplexed microarray immunoassay prototype (MosaiQ AiPlex CTDplus), used with the fully automated MosaiQ® system, for the simultaneous detection of fifteen autoantibodies associated with CTD, compared with selected CE-marked devices. Methods Banked human serum samples, characterized as reactive to ≥1 autoantibody or non-reactive were included. Reactive samples were characterized with FIDISTM Connective Profile (Theradiag) for CENP B, Jo-1, Ribosomal P, Scl-70, Sm, Sm/RNP, SS-A 60, TRIM21 (SS-A 52), SS-B and U1RNP; EliA CCP (Phadia) for CCP2, QUANTA Lite® Chromatin (Werfen) for Chromatin, QUANTA Flash® DFS70* (Werfen) for DFS70, Anti-dsDNA-IgG-ELISA (DRG) for dsDNA, and Immunodot (Euroimmun) for RNA polymerase III (RNAP III). For CCP2, only reactive samples were included. For the remaining analytes, non-reactive samples were characterized using immunofluorescence (ANA-Ro IgG FLUORESCENT HEp-2000®; Immuno Concepts, Germany) and ANAscreen ELISA (ORGENTEC-Diagnostika-GmbH, Germany). Each individual non-reactive sample was tested with the investigational device once; reactive samples were tested in duplicates. Positive percentage agreement (PPA) and negative percentage agreement (NPA) for individual analytes were calculated. For CCP2 only PPA is presented as no negative samples were included. Results Compared with relevant devices, the investigational prototype showed PPA ranging from 75% for chromatin to 99% for SS-A 60 and TRIM21. NPA ranged from 95% for chromatin, RNAP III, Scl-70 and Sm to 100% for DFS70, SS-A 60 and TRIM21. Performance details are shown in the Table. Conclusions The investigational prototype demonstrated substantial agreement with the compared CE-marked devices. Further studies will allow for expanded performance assessment of the investigational device. This fully-automated multiplexed platform has the potential to contribute to optimizing CTD evaluation by simplifying complex testing pathways and analyzing large number of samples per day.

#2646 Precision verification and method comparison of anti-MPO anti-hsPR3 immunoassay on Alegria2 instrument

Abstract Background and Aims Antibodies to myeloperoxidase (anti-MPO) and proteinase 3 (anti-PR3) are recognized as the only clinically relevant antineutrophil cytoplasmic antibodies (ANCA) specificities so far. ANCA testing can be used in different clinical settings, especially in situations that require rapid diagnosis like renal-pulmonary syndrome that require result within 24 hours. The aim of this study was to perform analytical verification of the new automated single test ELISA based method on Alegria2 instrument to test if the reagents and analyser were acceptable for the routine use. Method For precision assessment we tested two concentration levels of commercial control material in triplicate for five days in a row. We used EASI acceptable criteria for precision for anti-MPO as well as for anti-hsPR3. For method comparison we included 50 patients with history or suspicion of vasculitis. Anti-MPO and anti-PR3 were measured using 5 different reagents: Anti-Myeloperoxidase ELISA (IgG) and anti-PR3-hn-hr ELISA (IgG) on Euroimmun Analyzer I-2P (EUROIMMUN AG, Lubeck, Germany), MPO and PR3 II chemiluminiscent immunoassay (CLIA) on IDS iSYS (IDS ISYS, Pouilly en Auxois, France), QUANTA Flash® MPO and QUANTA Flash® PR3 CLIA on BIO-FLASH® (Inova Diagnostics Inc, San Diego, USA), Anti-MPO and anti-PR3 hs on Alegria2 ELISA based method (Orgentec, Mainz, Germany), and Anti-MPO and anti-PR3 ELISA (Orgentec, Mainz, Germany). Results were categorized as positive or negative and we calculated kappa statistics as well as intraclass correlation coefficient. Complete statistical analysis was done using MedCalc statistical software (MedCalc version 14.8.1, Ostend, Belgium). Results Within-laboratory precision (CV%) for anti-MPO for normal and pathological controls were 5.73% and 15.14% respectively. For anti-PR3 hs within-laboratory precision (CV%) for normal and pathological controls were 5.46% and 18.89% respectively. Intraclass correlation coefficient showed excellent degree of consistency in average measures (0.9778 (95% CI: 0.9665-0.9862)) for anti-MPO and good reliability on single ratings (0.8981 (95% CI: 0.8522-0.9344). For anti PR3 intraclass correlation coefficient showed excellent degree of consistency in average measures (0.9257 (95% CI: 0.8873-0.9539)) but only moderate consistency in single ratings (0.7136 (95% CI: 0.6115-0.8053)). Separate Cohen`s kappa testing revealed almost perfect agreement for most reagent combination for anti- MPO (kappa from 0.825 to 0.958). For anti-PR3 we found moderate agreement between QUANTA Flash® PR3 and PR3 II IDS iSYS (kappa 0.520) but mostly substantial agreement (kappa from 0.629 to 0.865). We also found almost perfect agreement between anti-PR3 hs on Alegria2 and QUANTA Flash® PR3 (kappa = 0.901). Conclusion Our results showed a rather small relative variability and met the precision criteria defined by EASI initiative. Satisfactory agreement between methods is very reassuring but due to the lack of standardisation in autoimmune diagnostics imposes that information about methodological differences must be clearly stated on laboratory report. According to our results the new method for anti-MPO and anti-PR3 proved to be suitable for the routine use.

Clinical Performance of Two Automated Immunoassays, EliA CTD Screen and QUANTA Flash CTD Screen Plus, for Antinuclear Antibody Screening.

BackgroundRecently, two fully automated immunoassays for antinuclear antibody (ANA) screening were introduced EliA CTD Screen (Thermo Fisher Scientific, Freiburg, Germany) and QUANTA Flash CTD Screen Plus (Inova Diagnostics, San Diego, USA). We evaluated their clinical performance in comparison with the indirect immunofluorescence assay (IIFA) and analyzed samples with discrepant results.MethodsIn total, 406 serum samples (206 from patients undergoing routine checkups and 200 from rheumatology clinic patients) were assayed using EliA, QUANTA Flash, and IIFA. We evaluated assay concordance and agreement and confirmed the presence of anti-extractable nuclear antigen (ENA) antibodies in samples with discrepant automated immunoassay and IIFA results. Additionally, we compared the clinical performance of each assay in diagnosing ANA-associated rheumatic disease (AARD) and adjusted the cut-off values.ResultsIn rheumatology clinic samples, the concordance and agreement were 91.5% and strong between EliA and QUANTA Flash, 79.0% and weak between EliA and IIFA, and 80.5% and moderate between QUANTA Flash and IIFA, respectively. In automated immunoassay-positive, IIFA-negative samples (N=15), all anti-ENA antibodies detected (6/15) were anti-Sjögren’s syndrome antigen A/Ro (Ro60) antibodies. The automated immunoassays and IIFA showed high accuracy for diagnosing AARD, and adjusted cut-off values improved their sensitivities (EliA with 0.56 ratio, 82.9% sensitivity; QUANTA Flash with 9.7 chemiluminescent units, 87.8% sensitivity).ConclusionsThe two automated immunoassays showed reliable performance compared with IIFA and can be efficiently used with the IIFA in clinical immunology laboratories. Clinical cut-off values can be adjusted according to the workflow in each laboratory.

Comparison of the analytical and clinical performances of four anti-cyclic citrullinated peptide antibody assays for diagnosing rheumatoid arthritis.

Anti-cyclic citrullinated peptide antibody (anti-CCP) is one of the most important serologic markers for diagnosing rheumatoid arthritis (RA). This study aimed to compare the analytical and clinical performances of the second- and third-generation anti-CCP assays. Four automated anti-CCP assays were evaluated: Chorus anti-CCP (Diesse Diagnostica), Elecsys anti-CCP (Roche Diagnostics), Atellica® IM anti-CCP IgG (Siemens Healthineers), and Quanta Flash® CCP3 (Inova Diagnostics Inc.). Analytical performance included the precision, linearity, correlation, and concordance rate. For evaluating the clinical performance, 240 patient samples (120 positive and 120 negative samples, determined by the Chorus anti-CCP assay) were used, including those with a diagnosis of RA (n = 132) and non-RA (n = 108). Using receiver operating characteristic (ROC) curve analysis, the sensitivity and specificity were evaluated. All four assays that were evaluated showed good precision and linearity, and their correlation and concordance rates were in acceptable ranges. The area under the curve (AUC) values ranged from 0.888 to 0.914, showing a good diagnostic performance. The sensitivity and specificity of all assays were similar (88.0-97.2%). All four anti-CCP assays showed good analytical and diagnostic performances for diagnosing RA. After adjusting the cutoff values, these assays are expected to show enhanced sensitivity and specificity. Key Points • Previous studies have described the diagnostic performance of a few immunologic markers in RA diagnosis, but nothing has been proven to be sufficiently good in clinical practice. • All four automated anti-CCP assays showed good analytical and diagnostic performances for diagnosing RA in clinical practice. • After adjusting the cutoff values, these assays are expected to show enhanced sensitivity and specificity. • The present study provides reassuring evidence that any of the studied commercially available anti-CCP tests for detecting rheumatoid arthritis provide similar diagnostic information to institutions that adopt these specific testing systems.

Detection of anti‐domain I antibodies by chemiluminescence enables the identification of high‐risk antiphospholipid syndrome patients: A multicenter multiplatform study

BackgroundClassification of the antiphospholipid syndrome (APS) relies predominantly on detecting antiphospholipid antibodies (aPLs). Antibodies against a domain I (DI) epitope of anti‐β2glycoprotein I (β2GPI) proved to be pathogenic, but are not included in the current classification criteria. ObjectivesInvestigate the clinical value of detecting anti‐DI IgG in APS. Patients/MethodsFrom eight European centers 1005 patients were enrolled. Anti‐cardiolipin (CL) and anti‐β2GPI were detected by four commercially available solid phase assays; anti‐DI IgG by the QUANTA Flash® β2GPI domain I assay. ResultsOdds ratios (ORs) of anti‐DI IgG for thrombosis and pregnancy morbidity proved to be higher than those of the conventional assays. Upon restriction to patients positive for anti‐β2GPI IgG, anti‐DI IgG positivity still resulted in significant ORs. When anti‐DI IgG was added to the criteria aPLs or used as a substitute for anti‐β2GPI IgG/anti‐CL IgG, ORs for clinical symptoms hardly improved. Upon removing anti‐DI positive patients, lupus anticoagulant remained significantly correlated with clinical complications. Anti‐DI IgG are mainly present in high‐risk triple positive patients, showing higher levels. Combined anti‐DI and triple positivity confers a higher risk for clinical symptoms compared to only triple positivity. ConclusionsDetection of anti‐DI IgG resulted in higher ORs for clinical manifestations than the current APS classification criteria. Regardless of the platform used to detect anti‐β2GPI/anti‐CL, addition of anti‐DI IgG measured by QUANTA Flash® did not improve the clinical associations, possibly due to reduced exposure of the pathogenic epitope of DI. Our results demonstrate that anti‐DI IgG potentially helps in identifying high‐risk patients.

Two Novel Technologies for the Detection of Anti-cardiolipin and Anti β2–Glycoprotein Antibodies in the Real Life: Chemiluminescent in Comparison to the Addressable Laser Bead Immunoassays

ABSTRACTIn the present study, we evaluated two novel technologies, the chemiluminescent immunoassay (CIA) QUANTA Flash on BIO-FLASH (Inova Diagnostics, San Diego, CA, USA) and the addressable laser bead immunoassay (ALBIA) on BioPlex™ 2200 (Bio-Rad, Hercules, CA, USA) for the detection of anti-cardiolipin IgG/IgM (aCL) and anti-β2–glycoprotein IgG/IgM (aβ2GPI) antibodies. The study was performed on 134 samples from consecutive patients (59 males and 75 females, mean age 54 ± 10 years) who consulted a rheumatologist because thrombosis and/or pregnancy complications were present or another immunological disease (Sjogren’s syndrome, inflammatory arthritis). Fourteen patients of the total fulfilled 25the Sydney criteria for APS and for these patients previous results of aPLs were available. Sera were tested for aCL and aβ2GPI of IgG and IgM isotypes using CIA (BIO-FLASH) and ALBIA (BioPlex™ 2200). Overall agreement between CIA and ALBIA ranged from 88.1% (aCL IgG) to 97.8% (aβ2GPI IgG). Cohen’s kappa coefficient ranged from 0.53 to 0.91, implying moderate to almost perfect agreement. Almost perfect agreement was found between BioPlex™ 2200 and BIO-FLASH aβ2GPI IgG and aCL IgM with Cohen’s kappa of 0.91 and 0.88, respectively. On the other hand, moderate agreement was found between BioPlex™ 2200 and BIO-FLASH aCL IgG and β2GPI IgM assays with Cohen’s kappa of 0.57 and 0.53, respectively. The two novel technologies look promising and comparable but further studies with larger cohorts are needed to contribute to the better understanding of the new aPLs antibodies assays performance.

Comparison of second- and third-generation immunoassays for detection of anti-cyclic citrullinated peptide antibodies

Anti-cyclic citrullinated peptide antibodies (anti-CCPs) are important diagnostic markers for rheumatoid arthritis (RA). We evaluated the analytical and clinical performance of the QUANTA Flash CCP3 (INOVA Diagnostics, USA), a fully automated third-generation anti-CCP assay, in comparison with three second-generation anti-CCP (CCP2) assays. A total of 300 sera (67 from RA patients, 64 from other rheumatic diseases, 43 from osteoarthritis [OA], and 126 from other conditions) were tested with QUANTA Flash CCP3, Kallestad Anti-CCP II (Bio-Rad, USA), Elecsys Anti-CCP (Roche Diagnostics GmbH, Germany), and ARCHITECT Anti-CCP (Abbott Diagnostics, USA). Within-run and total imprecision (% coefficient of variation) of the QUANTA Flash CCP3 were <6%, and its linearity was acceptable over the claimed range (4.0–2,749.7 chemiluminescent units). The frequency of anti-CCP was similar between QUANTA Flash CCP3 and the other CCP2 assays in the RA (67.2% vs. 62.7–70.1%), other rheumatic diseases (7.8% vs. 6.3%), and OA (2.3% vs. 0–2.3%) groups. The concordance rate between QUANTA Flash CCP3 and the other assays ranged from 96.3% to 97.7% (kappa from 0.87 to 0.92). For the diagnosis of RA, the sensitivity/specificity was 67.2%/95.7%, 62.7%/98.3%, 70.2%/96.6%, and 67.2%/97.9%, and the areas under the receiver operating characteristic curves were 0.851, 0.791, 0.853, and 0.867 for QUANTA Flash CCP3, Kallestad, Elecsys, and ARCHITECT assays, respectively. The performance of the QUANTA Flash CCP3 was satisfactory and comparable to that of the three CCP2 assays. This fully automated assay would be a practical and reasonable option in clinical laboratories.

Anti-DFS70 among HIV-positive individuals - A prospective study.

Anti-DFS70 is an anti-nuclear antibody directed against the DFS70 protein, which is produced in response to several stressful events. Since its discovery, this autoantigen-antibody complex has drawn the attention of many researchers, yet many questions remain unanswered. The DFS70 protein is crucial for HIV integration into the host DNA; however, the relationship between anti-DFS70 and HIV is unknown. A protective role of anti-DFS70 against HIV is possible due to the competition between the HIV integrase and the anti-DFS70 antibody on the same target site on DFS70. The current study aimed to assess the prevalence of anti-DFS70 in HIV-positive individuals seeking for possible interrelation. A total of 100 HIV-positive individuals followed up at the HIV unit at Sheba Medical Center were tested for the detection of anti-DFS70. A total of 92 non-HIV subjects, randomly selected, were tested and compared as controls. Chemiluminescence assay by QUANTA Flash was performed to evaluate the presence of anti-DFS70 antibodies. None of the HIV-positive individuals had a positive test result for anti-DFS70 (0%) compared to 10 out of 92 non-HIV individuals (10.9%). This is the first study addressing the prevalence of anti-DFS70 in HIV-positive patients. The rate of anti-DFS70 positivity was found to be significantly lower in HIV-positive individuals than in non-HIV individuals (p=0.002). The absence of anti-DFS70 in HIV-positive subjects might imply that individuals who lack these antibodies are more susceptible to HIV infection. Further studies with large populations are needed to confirm this hypothesis.

Clinical value of anti-domain I-β2Glycoprotein 1 antibodies in antiphospholipid antibody carriers. A single centre, prospective observational follow-up study

BackgroundThere seems to be a clear correlation between antibodies against domain I (anti-DI) of β2Glycoprotein I and severe clinical profiles in antiphospholipid syndrome (APS) patients. We investigated the clinical significance of anti-DI antibodies in a cohort of aPL carriers. MethodsOne hundred and five carriers persistently positive for IgG anti-β2Glycoprotein 1 antibodies (a-β2GPI) and/or IgG anticardiolipin (aCL) and/or lupus anticoagulants (LAC) were tested for the presence of anti-DI antibodies using the QUANTA Flash® Beta2GPI-Domain I chemiluminescence immunoassay. ResultsAnti-DI antibodies were detected in 44 aPL carriers (41.9%) and they were significantly associated to triple aPL positivity (LAC plus IgG a-β2GPI plus IgG aCL antibodies). Isolated LAC and a-β2GPI antibodies were significantly associated to anti-DI negative aPL carriers. During a 82.2 month mean follow-up, ten aPL carriers (9.5%) developed a first thrombotic event so becoming APS patients. Anti-DI antibodies, triple aPL positivity, thromboembolic risk factors and autoimmune disorders significantly prevailed in carriers becoming APS. Logistic regression analysis showed that anti-DI positivity was an independent risk factor for thrombosis. ConclusionsAnti-DI antibody positivity can be considered a new risk factor predictive of the first thrombotic event in aPL carriers, instead, negative anti-DI may be useful to identify low-risk aPL carriers.

Comparison of Serological Biomarkers in Rheumatoid Arthritis and Their Combination to Improve Diagnostic Performance.

The diagnosis of rheumatoid arthritis (RA) is based on a combined approach that includes serological markers such as rheumatoid factor (RF) and anti-citrullinated peptide/protein antibodies (ACPA). The goal of this study was to evaluate the clinical performance of several RF and ACPA immunoassays for the diagnosis of RA, as well as the diagnostic value of a combinatory approach with these markers. The study cohort included 1,655 patients from the Swiss Clinical Quality Management registry with sera from 968 patients with RA and 687 disease controls, including patients with axial spondyloarthritis (n = 450) and psoriatic arthritis (n = 237). ACPA were determined by anti-CCP2 IgG enzyme-linked immunosorbent assay (ELISA), QUANTA Flash® CCP3 IgG [chemiluminescent immunoassay (CIA)], and QUANTA Lite® CCP3 IgG ELISA. RF was determined by ELISA (QUANTA Lite® RF IgM, RF IgA, and RF IgG) and with two research use only CIAs (QUANTA Flash® RF IgM and RF IgA). All three ACPA assays showed good discrimination between RA patients and controls and good clinical performance. Overall, CCP3 performed better than CCP2. More pronounced differences were observed between the RF assays. We observed that CIA platforms for both RF IgM and RF IgA showed better performance than the ELISA platforms. Excellent and good total agreements were found between ELISA and CIA for CCP3 (total agreement 95.3%, kappa = 0.90), and between CCP2 and CCP3 ELISA (total agreement 86.6%, kappa = 0.73), respectively. RF IgM CIA and ELISA had a good qualitative agreement (86.5%, kappa = 0.73); RF IgA CIA and ELISA showed a moderate total agreement (78.5%, kappa = 0.53). When combinatory analyses were performed, the likelihood of RA increased with dual positivity and triple positivity and combining different markers resulted in higher odds ratio than the individual markers in all cases. ACPA and RF showed good clinical performance in this large Swiss cohort of RA patients and controls. Overall, the performance of CCP3 was superior to CCP2. The combination of these biomarkers in an interval model represents a potential tool for the diagnosis of RA patients.

Evaluation of classical and novel autoantibodies for the diagnosis of Primary Biliary Cholangitis-Autoimmune Hepatitis Overlap Syndrome (PBC-AIH OS).

Background and aimsUp to 20% of Primary Biliary Cholangitis (PBC) patients are estimated to have features that overlap with Autoimmune Hepatitis (AIH). Patients with PBC-AIH overlap syndrome (PBC-AIH OS) have been reported to exhibit suboptimal responses to ursodeoxycholic acid therapy, and are more likely to progress to cirrhosis. Anti-double stranded DNA (anti-dsDNA) and anti-p53 have been previously suggested to be potential autoantibodies for identifying patients with PBC-AIH OS. In our well defined PBC patient cohorts, a comprehensive assessment of various classical and novel autoantibodies was evaluated for their utility in identifying PBC-AIH OS patients.MethodsPBC-AIH OS was classified according to the Paris criteria and PBC as per the European Association for the Study of the Liver guidelines. Biobanked serum samples from 197 patients at the University of Calgary Liver Unit and the University of Alberta were analyzed for classical and novel autoantibodies. Anti-dsDNA was measured by the Crithidia luciliae immunofluorescence (CLIFT) assay (1:20 dilution) and chemiluminescence (CIA: QUANTA Flash®, Inova Diagnostics, San Diego). Anti-p53, anti-Ro52/TRIM21, anti-YB 1, anti-GW182, anti-Ge-1, and anti-Ago 2 were measured by either an addressable laser bead immunoassay (ALBIA) or line immunoassay (LIA). Autoantibodies against MIT3, gp210, sp100, LKM1, SLA, and the novel autoantibodies Hexokinase-1 (HK-1), and Kelch like protein 12 (KLHL-12) were measured using QUANTA Lite® ELISA assays. We applied non-parametric methods to compare the biomarkers frequencies between study groups. We used multivariate adjusted models and AUROC to compare the diagnostic accuracy of the different autoantibodies alone or in combination with serum biochemistry.Results16 out of 197 PBC patients (8.1%) were classified as PBC-AIH OS. Compared to PBC patients, PBC-AIH OS patients were similar in age (median: 59 vs. 63, P = 0.21) and female predominance (94% vs. 89%, P = 1.00). Anti-dsDNA-by CLIFT (37.5% in PBC-AIH OS vs 9.9% in PBC alone, P <0.01) was the only autoantibody associated with PBC-AIH OS; a finding consistent with previous reports. Significant elevation in serum ALT (62 IU/L in PBC-AIH OS vs 37 IU/L in PBC alone, P < 0.01), and serum IgG (17.6 g/L in OS vs 12.1 g/L in PBC alone, P <0.01) were observed in patients with PBC-AIH OS receiving medical/immunosuppressive therapy. In a multivariate model, positive anti-dsDNA by CLIFT, ALT and IgG were significant predictors of PBC-AIH OS with an area under the receiver operator curve (AUROC) value of 0.84.ConclusionsConsistent with previous findings, the presence of anti-dsDNA by CLIFT is associated with PBC-AIH OS. Contrary to previous reports, anti-p53 was not associated with PBC-AIH OS. Our comprehensive evaluation of various classical and novel autoantibody biomarkers including Ro52/TRIM21, anti-p53, anti-KLHL-12 and anti-HK-1 were not significantly associated with PBC-AIH OS. Our findings highlight the ongoing need for the research and development of new autoantibody biomarkers to aid in the diagnosis of PBC-AIH OS.

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.

Beyond thrombosis: Anti-β2GPI domain 1 antibodies identify late pregnancy morbidity in anti-phospholipid syndrome

Antibodies against β2 glycoprotein I (anti-β2GPI) have been identified as the main pathogenic autoantibody subset in anti-phospholipid syndrome (APS); the most relevant epitope is a cryptic and conformation-dependent structure on β2GPI domain (D) 1. Anti-β2GPI domain profiling has been investigated in thrombotic APS, leading to the identification of antibodies targeting D1 as the main subpopulation. In contrast, scarce attention has been paid to obstetric APS, hence this study aimed at characterizing the domain reactivity with regards to pregnancy morbidity (PM).To this end, 135 women with persistently positive, medium/high titre anti-β2GPI IgG, without any associated systemic autoimmune diseases and at least one previous pregnancy were included: 27 asymptomatic carriers; 53 women with obstetric APS; 20 women with thrombotic APS; and 35 women with both thrombotic and obstetric complications. Anti-D1 and anti-D4/5 antibodies were tested using a chemiluminescent immunoassay and a research ELISA assay, respectively (QUANTA Flash® β2GPI Domain 1 IgG and QUANTA Lite® β2GPI D4/5 IgG, Inova Diagnostics).Positivity for anti-D1 antibodies, but not anti-D4/5 antibodies, was differently distributed across the 4 subgroups of patients (p < 0.0001) and significantly correlated with thrombosis (χ2 = 17.28, p < 0.0001) and PM (χ2 = 4.28, p = 0.039). Patients with triple positivity for anti-phospholipid antibodies displayed higher anti-D1 titres and lower anti-D4/5 titres compared to women with one or two positive tests (p < 0.0001 and p = 0.005, respectively). Reactivity against D1 was identified as a predictor for PM (OR 2.4, 95% confidence interval [CI] 1.2–5.0, p = 0.017); in particular, anti-D1 antibodies were predictive of late PM, conveying an odds ratio of 7.3 (95% CI 2.1–25.5, p = 0.022). Positivity for anti-D1 antibodies was not associated with early pregnancy loss. Anti-D4/5 antibodies were not associated with clinical APS manifestations.As a whole, our data suggest that anti-D1 antibodies are significantly associated not only with thrombosis, but also with late PM, while positive anti-D4/5 antibodies are not predictive of thrombosis or PM.

Anti-citrullinated protein antibodies in the diagnosis of rheumatoid arthritis (RA): diagnostic performance of automated anti-CCP-2 and anti-CCP-3 antibodies assays

This study compares the diagnostic performance of a second generation anti-cyclic citrullinated peptide antibody (CCP2) with a third generation anti-CCP antibodies assay (CCP3), as well as the combination of both tests. Serum samples of 127 patients were analyzed. IgG anti-CCP 2 and IgM rheumatoid factor were determined by EliA™ technique on a Phadia 250 instrument (Thermo Fisher Scientific), anti-CCP3 by the Quanta Flash™ anti-CCP3 IgG kit, BIO-FLASH Rapid Response Chemiluminscence Analyzer (INOVA Diagnostics). Diagnostic performance was compared using ROC-curves, sensitivity, specificity, likelihood ratios, and predictive values. Logistic regressions were used to investigate whether using both tests (anti-CCP2 and anti-CCP3) gives a better prediction of rheumatoid arthritis. At the manufacturer’s cut-offs sensitivity and specificity were 79.4 and 61.0% for CCP3 and 80.9 and 69.5% for CCP2. No significant differences could be observed regarding the areas under the curve (AUC) of both ROC-curves. The optimal cut-off point for CCP2 was 10.5 U/ml (sensitivity of 75.0% and specificity of 80.0%) and 5.6 U/ml for CCP3 (sensitivity of 86.9% and specificity of 61.0%). Binary logistic regressions indicated that the likelihood of having rheumatoid arthritis (RA) is significantly higher when testing positive on both CCP2 and CCP3 compared to CCP2 or CCP3 alone. In our cohort, comparable performance was found between the two CCP assays. Positivity for both CCP2 and CCP3 resulted in the most specific identification of RA patients. In patients with joint complaints suspected of having RA and with a weakly positive CCP 2 (≥7 and ≤16 U/ml) CCP3 testing could be of additive value for diagnosing RA.

Comparison of enzyme-linked immunosorbent assay and rapid chemiluminescent analyser in the detection of myeloperoxidase and proteinase 3 autoantibodies

Antibodies to myeloperoxidase (MPO) and proteinase 3 (PR3) are vital in the diagnosis and management of ANCA-associated vasculitis. A chemiluminescent immunoassay (CLIA; Quanta Flash) provides MPO and PR3 antibody results in 30 minutes, which is much faster than enzyme-linked immunosorbent assay (ELISA). We compared the performance of ELISA (Orgentec) and CLIA (Quanta Flash) for MPO and PR3 antibody quantitation on 303 samples, comprising 196 consecutive samples received in a single diagnostic laboratory over a 3 month period, and 107 samples collected from 42 known vasculitis patients over a 40 month period. We observed a correlation between both methods using spearman correlation coefficients (MPO, rs=0.63, p<0.01; PR3, rs=0.69, p<0.01). There was agreement between both methods in determining a positive or negative result. In the vasculitis cohort, CLIA performed well at clinically important stages of disease; diagnosis (eight samples all positive by both assays) and disease relapse (correlation for both MPO and PR3 antibody quantitation rs=0.84, p=0.03 and rs=0.78, p<0.01, respectively). Three samples were discordant at clinical relapse, testing positive by CLIA, including one high positive associated with relapse requiring a change in treatment. In summary, CLIA appears to be at least as accurate as ELISA for measurement of MPO and PR3 antibodies.

Performance Characteristics of Different Anti-Double-Stranded DNA Antibody Assays in the Monitoring of Systemic Lupus Erythematosus.

Objective We sought to evaluate different anti-double-stranded DNA assays for their performance characteristics in monitoring disease activity fluctuations in systemic lupus erythematosus (SLE). Methods 36 active SLE patients were followed monthly. At each study visit (total n = 371), blood was collected and disease activity was scored using the SELENA-SLEDAI (excluding anti-dsDNA or complement components) and by a physician's global assessment (PGA). Four anti-dsDNA tests were compared. Linear mixed-effects models with random intercept and fixed slopes were used to evaluate the relationship between the longitudinal fluctuations of disease activity and anti-dsDNA titers. Results At enrollment, positivity for QUANTA Lite and high-avidity anti-dsDNA assay was both 64% and significantly lower than anti-dsDNA positivity by QUANTA Flash (83%) and CLIFT (96%). Linear mixed-effects modeling indicated that the change in clinical SELENA-SLEDAI scores was associated with the titers of all anti-dsDNA with QUANTA Flash yielding the highest marginal R2 (0.15; p < 0.01). QUANTA Flash was the only anti-dsDNA assay significantly associated with the change in PGA (marginal R2 = 0.05; p < 0.01). Conclusion These data indicate that anti-dsDNA antibodies determined by QUANTA Flash have a value in monitoring SLE disease activity.

Role of anti‐domain 1‐β2glycoprotein I antibodies in the diagnosis and risk stratification of antiphospholipid syndrome

Essentials Antibodies to domain 1 of β2 glycoprotein I (aD1) are a subset of antiphospholipid antibodies. We evaluated the added diagnostic value of an automated aD1 assay in antiphospholipid syndrome. AD1 IgG correctly classifies patients at risk for thrombosis. Agreement between aD1 and aβ2GPI IgG is high, limiting the added value of aD1 in our setting. Click to hear Professor de Groot's perspective on new mechanistic understanding in antiphospholipid syndrome Background Laboratory diagnosis of antiphospholipid syndrome (APS) includes lupus anticoagulant (LAC), anticardiolipin (aCL) or anti-β2 glycoprotein I (aβ2 GPI) antibodies. Antibodies targeting domain 1 of β2 GPI (aD1) constitute a pathogenic subset of autoantibodies. Objectives In this cohort study, we determined the clinical performance characteristics, additional diagnostic value and the contribution to APS risk stratification of an automated aD1 assay. Patients/Methods LAC, aCL, aβ2 GPI and aD1 IgG were measured in 101 APS patients, 123 patients with autoimmune disorders, 82 diseased controls and 120 healthy controls. aD1 antibodies were detected by QUANTA Flash(®) Beta2GPI-Domain 1 chemiluminescence immunoassay. Results With a cut-off value of 20.0 CU, the aD1 IgG assay identifies APS patients in a clinically affected patient cohort with a sensitivity of 53.5% and specificity of 98.8%. It implied a high odds ratio (OR) for clinical events (OR, 17.0; 95% confidence interval [CI], 7.1-40.5). aD1 IgG did not add diagnostic value to the formal aPL panel because aβ2 GPI IgG was nearly as specific but more sensitive for APS (sensitivity 56.4%) with a higher OR for clinical events (36.2; 95% CI, 11.1-117.9). High aD1 titers identify triple-positive patients and patients with thrombosis in a β2 GPI-dependent LAC-positive population. Agreement between aD1 IgG and aβ2 GPI IgG was high (positive and negative agreement 91.7% and 98.4%, respectively). Conclusion Detection of aD1 IgG correctly classifies patients at risk of thrombosis. However, the contribution of aD1 IgG to APS diagnosis and risk stratification depends upon the solid phase assays used for aCL and aβ2 GPI detection.

Fully-automated, chemiluminescence IgA and IgG anti-tissue transglutaminase (tTG) antibodies serum assays for the screening of celiac disease

AimCeliac disease (CD) is a systemic immune-mediated enteropathy sustained by gluten ingestion in genetically susceptible subjects. The European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) has recently revised the diagnostic criteria, emphasizing the crucial role of serological testing in the diagnosis of this condition. This study was hence aimed to evaluate a new chemiluminescence assay for measuring anti-transglutaminase (tTG) and anti-endomysium (EMA) antibodies in a general population of unselected outpatients. Materials and methodsThe IgA and IgG anti-tissue transglutaminase (tTG) antibodies (Quanta Flash® IgA and Quanta Flash® IgG tTG, Inova Diagnostics, San Diego, CA, USA) were measured with the fully-automated BIO-FLASH® analyzer (Inova Diagnostics) in serum samples of 727 consecutive patients without a diagnosis of CD. Data were compared with those of anti-endomysium antibody (EmA) obtained in the same population. ResultsA total of 96.4% samples display a negative concordance (anti-tTG negative and EMA negative), O% were positive for EMA and negative for anti-tTG IgA and IgG, 3.6% were both positive for tTG IgA and EMA, whereas 0.6% displayed discordant results (positive for anti-tTG and negative for EMA). The concordance (99%) and inter-rater agreement (Kappa Statistics, 0.943; p<0.001) between anti-tTG IgA and EmA antibodies were excellent, with sensitivity and specificity of 99% and 100%, respectively. ConclusionThe results of this study show that Quanta Flash® IgA assay alone may be regarded as a reliable approach for screening of CD, with no need to perform EMA detection.

Clinical evaluation of a novel chemiluminescent immunoassay for the detection of anti-citrullinated peptide antibodies

BackgroundWe evaluated the analytical and clinical performances of a novel, automated chemiluminescent immunoassay in comparison with several anti-citrullinated protein antibody (ACPA) assays (2nd and 3rd generations) based on various platforms and technologies. MethodsSamples from rheumatoid arthritis (RA) patients (n=141) and controls (n=153) were collected based on an ordered ACPA test. All samples were tested with QUANTA Flash® CCP3, QUANTA Lite® CCP3, QUANTA Lite® CCP3.1, CCPlus and EliA® CCP assays. Rheumatoid factor (RF) was determined using Quantex RF(II). An additional cohort consisting of RA patients from three different sources (116, 79 and 50 samples), 61 juvenile idiopathic arthritis (JIA) patients and 233 controls were used in an extended evaluation on QUANTA Flash® CCP3 only. Precision and linearity of the QUANTA Flash® CCP3 were assessed according to CLSI guidelines. ResultsAll ACPA assays showed good qualitative and quantitative agreements. The Quanta Flash CCP3 assay showed good analytical and clinical performance. Based on the extended cohort, the sensitivity, specificity and likelihood ratios of the novel Quanta Flash® CCP3 were defined as 70.2%, 97.4% and 27.3/0.31, respectively. ConclusionGood agreements between different ACPA assays based on diverse platforms were found. Quanta Flash CCP3 is a reliable test for the fully automated and rapid detection of ACPA.