Comparison between multiplex assays for autoantibody detection in systemic lupus erythematosus

Potential biomarkers for diagnosis and assessment of disease activity in systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease involving multiple system functions. Our study aimed to screen out more effective new indicators that can assist clinical diagnosis and judge disease activity.

METHODS

We first screened serum levels of 45 cytokines of SLE patients (n = 3) and healthy controls (n = 3). Subsequently, we selected five elevated cytokines for verification with an expanded sample size. Then, the relationship between cytokines and laboratory parameters was also investigated. Finally, we used receiver operating characteristic (ROC) curves to assess the clinical value of these cytokines.

RESULTS

Through screening of 45 cytokines, 15 were found to be elevated in SLE patients. We chose five cytokines (IL-6, IL-10, IL-1RA, IP-10 and LIF) for further research and found elevated expression of all five cytokines in SLE patients. Serum levels of IL-10, IL-1RA and LIF were positively correlated with SLEDAI-2K score. Besides, the level of IL-10 was significantly positively correlated with serum IgG and erythrocyte sedimentation rate (ESR); IL-1RA was significantly negatively correlated with C3 and C4; and LIF was significantly positively correlated with serum IgG, C-reactive protein (CRP), and ESR. Furthermore, IL-1RA and LIF were strongly positively correlated with 24-hour urine protein levels. The ROC analysis showed that IL-1RA has good diagnostic value, and IL-10 and LIF levels can be utilized to discriminate between active and inactive SLE.

CONCLUSION

IL-1RA can be used as a biomarker for diagnosing SLE, while IL-10 and LIF can be indicators to discriminate between active and inactive SLE.

Laboratory evaluation of anti-dsDNA antibodies

Antibodies to dsDNA are an important laboratory parameter for diagnosis, monitoring and classification of systemic lupus erythematosus (SLE). In clinical laboratories, several techniques are used to detect and quantify anti-dsDNA antibodies. Each technique has its advantages and disadvantages regarding sensitivity, specificity, avidity and assay procedure. Assays differ with respect to the antigen source (native versus synthetic versus molecular biological) used and the way the antigen is presented (e.g. in solution, covalently linked to a solid phase,…). Consequently, correlation between assays can be poor and standardization of anti-dsDNA antibody tests is challenging. We here provide an overview of the currently available anti-dsDNA tests frequently used in clinical laboratories [Crithidiae luciliae immunofluorescence test (CLIFT), Enzyme linked immune sorbent assay (ELISA), fluoroenzyme immunoassay (FEIA), chemiluminescence (CIA), multiplexed bead-based assays and Farr-RIA] and their performance characteristics. From this literature study, we concluded that performance characteristics differ between assays. Often, a combination of techniques is necessary for the best result interpretation.

Clinical and serological associations of autoantibodies in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by the formation of antigen-antibody complexes which trigger an immune response. We investigate certain autoantibodies including nucleosome, double-stranded DNA (dsDNA), Smith, ribonucleoprotein, and Sjögren's syndrome-related antigens, and examine their associations with disease activity, damage accrual, and SLE-related clinical and serological manifestations in patients with SLE. We conducted a cross-sectional study with a total 293 patients (90.4% female, mean age 46.87±12.94 years) and used the Systemic Lupus Erythematosus Disease Activity Index 2000 and Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI) to evaluate disease activity and disease-related damage, respectively. Systemic Lupus Erythematosus Disease Activity Index scores were significantly higher in anti-nucleosome-positive (3.87±2.72 vs 2.52±2.76, p=0.004) and anti-dsDNA-positive (3.08±2.91 vs 2.04±2.48, p=0.010) patients compared with patients without these antibodies. SDI scores were also significantly higher in anti-nucleosome-positive patients (1.61±1.99 vs 0.89±1.06, p=0.004). The presence of antinucleosome (p=0.019) and anti-dsDNA antibodies (p=0.001) both correlated significantly with the incidence of nephritis; anti-La antibodies were associated with arthritis (p=0.022), and we also observed a relationship between the presence of antinucleosome antibodies and leukopenia (p=0.011). Patients with antinucleosome or anti-dsDNA antibodies had a higher disease activity and were likely to have nephritis. Antinucleosome was also associated with more damage accrual. A greater understanding of these autoantibodies could lead to the development of new approaches to more accurate assessments of SLE.

Performance of Anti-Topoisomerase I Antibody Testing by Multiple-Bead, Enzyme-Linked Immunosorbent Assay and Immunodiffusion in a University Setting

BACKGROUND/OBJECTIVE

The criterion standard for anti-topoisomerase I antibody (anti-topo I antibody) testing in systemic sclerosis (SSc) uses immunodiffusion (ID) techniques, but enzyme-linked immunosorbent assay (ELISA) and multiple-bead technology are often used in current settings to save time and cost. Our aim was to assess the performance of the multiple-bead assay, ELISA, and ID testing methods.

METHODS

We conducted a retrospective study of patients at the University of Michigan whose extractable nuclear antigen 10 autoantibody panel tested positive for the anti-topo I antibody by multiple-bead technology during a 1-year period. All samples positive by multiple-bead assay were sent to the RDL Laboratories and reflexed for ELISA, and all anti-topo I antibodies positive by ELISA were further tested by ID. Clinical data were reviewed by a rheumatologist and assessed for presence of SSc. Data were analyzed via frequency tables.

RESULTS

Approximately 9500 extractable nuclear antigen 10 panels were ordered by physicians at the University of Michigan. Of these, 129 patients were positive for the anti-topo I antibody by multiple-bead assay, 51 were positive by multiple-bead assay and ELISA, and 21 were positive by multiple-bead assay, ELISA, and ID. We found that 26.4% of patients positive by multiple-bead assay, 47.1% positive by multiple-bead assay and ELISA, and 95.2% positive by multiple-bead assay, ELISA, and ID had SSc.

CONCLUSIONS

Multiple-bead assays have a high rate of false-positive results for the anti-topo I antibody in patients without clinical evidence of SSc. A stepwise approach of confirmation of positive multiple-bead assay results using both ELISA and ID improves the predictive value of antibody testing for the diagnosis of SSc.

Development of a Novel Multiplex Bead-based Assay for Measuring Autoantibodies on Flow Cytometric Platform

Background: Autoantibodies (AAbs) are important biomarkers for the diagnosis of Autoimmune Diseases (ADs). The detection of AAbs performed by current methods (indirect immunofluorescence test (IIFT)/Immunoblot (dot/line)/enzyme-linked immunosorbent assay ELISA) which have limitations in terms of performing multiple assays to arrive at laboratory diagnosis. We validated a novel multiplex bead-based assay (NMBA) that could quantify five common antibodies, simultaneously, on a flow-cytometry platform.Methods: A total of five recombinant antigens (SS-A Ro60, CENP B, RNP 70, Scl 70 and Histones) were covalently coupled onto beads and tested using known positive sera (positive for AAbs) and analyzed using flow cytometer.Results: The sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) were obtained for each antigen, analyzed by both assays (NMBA and IIFT). It showed comparable or higher values for the NMBA. The Spearman's rank correlation coefficient (Rho) were ≥ 0.97, (P < .05), indicating that multiplexing of the five autoantigens did not alter the results obtained when antigens were tested individually. The mean intra-assay precision measured by coefficient of variation (CV) was7.56 ± 1.6% and the mean inter-assay CV was 10.03 ± 1.34%. The time taken from sample receipt to reporting of results was 90 minutes in NMBA as compared to 150 minutes of IIFTConclusion: The NMBA could quantitatively measure antibodies against five autoantigens, simultaneously in patient's sera. The assay is faster, objective, reproducible, requires low sample volume, and stable. Moreover, the flow cytometer in diagnostic laboratory settings for hematological and transplant immunology tests, can also be used for testing AAbs.

Prevalence of autoantibody responses in acute coronavirus disease 2019 (COVID-19)

Immunopathology may play a significant role in the pathogenesis of Coronavirus-Induced Disease-19 (COVID-19). Immune-mediated tissue damage could result from development of rapid autoimmune responses, characterized by production of self-reactive autoantibodies. In this study, we tested specimens from acutely ill patients hospitalized with COVID-19 for autoantibodies against nuclear, vasculitis-associated, and phospholipid antigens. Detectable autoantibodies were present in 30% of the patients in our cohort, with the majority of reactive specimens demonstrating antibodies to nuclear antigens. However, antinuclear antibodies were only weakly reactive and directed to single antigens, as is often seen during acute infection. We identified strongly reactive antibodies to nuclear antigens only in patients with a prior history of autoimmune disease. In our cohort, the prevalence of antiphospholipid antibodies was low, and we did not detect any vasculitis-associated autoantibodies. We found similar levels of inflammatory markers and total immunoglobulin levels in autoantibody positive versus negative patients, but anti-SARS-CoV-2 antibody levels were increased in autoantibody positive patients. Together, our results suggest that acute COVID-19 is not associated with a high prevalence of clinically significant autoantibody responses of the type usually associated with autoimmune rheumatic disease.

•

Autoantibodies against nuclear antigens are detectable in 25% of patients hospitalized with acute COVID-19.

•

Anti-nuclear antigen antibodies were weakly reactive and most often directed to single antigens.

•

Vasculitis-associated autoantibodies were not detected in specimens from patients with acute COVID-19.

•

Anti-phospholipid antibodies were infrequently detected in patients with acute COVID-19.

Anti-Ro52 Autoantibodies Are Related to Chronic Graft-vs.-Host Disease After Allogeneic Hematopoietic Stem Cell Transplantation

Chronic graft-vs.-host disease (cGVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Previous studies have shown that autoantibodies play an important role in the development of cGVHD. Anti-nuclear autoantibodies (ANA) is the most frequently detected autoantibodies in patients with cGVHD, but the role of anti-Ro52 autoantibodies (anti-Ro52) in cGVHD remains largely unknown. In this study, we analyzed autoantibodies from 84 patients after allo-HSCT, including 42 with active cGVHD and 42 without cGVHD. Autoantibodies were found in 36 (42.9%) patients. Among these autoantibody-positive patients, 28 (77.8%) patients had active cGVHD. The most frequent autoantibodies in patients with active cGVHD were ANA (50.0%), anti-Ro52 (28.6%) and anti-mitochondrial autoantibodies type 2 (4.8%). We further explored the association between anti-Ro52 and cGVHD. Patients with active cGVHD had higher anti-Ro52 levels than patients without cGVHD (P < 0.05). The increases of anti-Ro52 levels were more significant in patients with moderate/severe cGVHD compared to those of patients without cGVHD (P < 0.05). Stratified and multivariable logistic regression analysis demonstrated that moderate/severe cGVHD was an independent risk factor for the levels of anti-Ro52 (P < 0.01). ROC analysis confirmed anti-Ro52 as a risk factor for progression of skin cGVHD. Moreover, the anti-Ro52 levels were highly correlated with the levels of B cell-activating factor (BAFF) and IgG1 antibodies. Our study demonstrates that anti-Ro52 is associated with cGVHD. The increased levels of anti-Ro52 were associated with higher levels of BAFF and IgG1 antibodies, suggesting a mechanistic link between elevated anti-Ro52 levels and aberrant B cell homeostasis.

Predictive autoimmunity using autoantibodies: screening for anti-nuclear antibodies

Background:

Early detection of antinuclear antibodies (ANA) in asymptomatic subjects is useful to predict autoimmune diseases years before diagnosis. ANA have been determined by indirect immunofluorescence (IIF) using human epithelial type 2 (HEp-2) cells, which is considered the gold standard technique. Multiplex technology (BioPlex ANA Screen) has been introduced for ANA evaluation in recent years. Nevertheless, concordance between BioPlex and IIF is low and there is no harmonization between both methods for detection of autoantibodies. This study has aimed to clarify the clinical significance of autoantibodies detected by BioPlex ANA Screen in subjects with undiagnosed clinical suspicion of autoimmune disease and to determine the predictive value of autoantibodies detected by BioPlex ANA Screen.

Methods:

A 3-year follow-up study was performed of 411 subjects without a clear diagnosis of autoimmune diseases in whom autoantibodies were detected by BioPlex ANA Screen that were negative by IIF on HEp-2 cells.

Results:

At 3 years of follow-up, 312 (76%) subjects were positive for autoantibodies by IIF and 99 subjects continued to be negative. A diagnosis of autoimmune disease was found in most of the subjects (87%).

Conclusions:

BioPlex ANA Screen has greater sensitivity than IIF on HEp-2 cells for autoantibodies detection. Early detection of these antibodies by BioPlex can predict possible development of autoimmune diseases.

Detection of SSA and SSB Antibodies Associated with Primary Sjögren's Syndrome Using Enzyme-Linked Immunosorbent Assay

Antibodies to Ro52/Ro60 (SSA) and La (SSB) are strongly associated to the autoimmune disease primary Sjögren's syndrome and are important in the serologic diagnosis of the disease. Several methods for detection of these antibodies exist such as indirect immunofluorescence, commercial western blot kits, in-house assays, and numerous commercial enzyme-linked immunosorbent assays (ELISAs). Dependent on the type of assay, sensitivity and specificity may vary notably. Especially ELISAs, where the antibody reactivity to synthetic peptides, recombinant or native proteins are determined, are often applied. This chapter describes detection of SSA and SSB antibodies by ELISA.

Cell-bound complement activation products (CB-CAPs) have high sensitivity and specificity in pediatric-onset systemic lupus erythematosus and correlate with disease activity

OBJECTIVE

Elevated levels of cell-bound complement activation products (CB-CAPs) (C4d deposition on B lymphocytes (BC4d) and/or erythrocytes (EC4d)) are sensitive and specific in diagnosis and monitoring of adult systemic lupus erythematosus (SLE). Our objective was to evaluate the role of CB-CAPs for diagnosis and monitoring of pediatric-onset SLE (pSLE).

METHODS

A prospective cohort study of 28 pSLE and 22 juvenile arthritis patients was conducted. SLE disease activity was determined using a clinical Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) that excluded serologies. Autoantibodies were measured using solid-phase immunoassays, C3 and C4 using immunoturbidimetry, and CB-CAPs using quantitative flow cytometry. Abnormal CB-CAPs were defined as EC4d or BC4d above the 99th percentile for healthy adults (>14 and > 60 net mean fluorescence intensity (MFI), respectively). Performance characteristics of CB-CAPs were assessed using area under the curve (AUC) for receiver operating characteristics. Linear mixed effect models evaluated the correlation between CB-CAPs and clinical SLEDAI over 6 months.

RESULTS

BC4d yielded higher AUC (0.91 ± 0.04) than C3 (0.63 ± 0.08) and C4 (0.67 ± 0.08) ( p < 0.05). Abnormal CB-CAPs were 78% sensitive and 86% specific for diagnosis of pSLE (Youden's index = 0.64 ± 0.11). In contrast to BC4d, EC4d levels correlated with clinical SLEDAI ( p < 0.01).

CONCLUSION

CB-CAPs (EC4d and BC4d) have higher sensitivity and specificity than low complement in pSLE, and may help with diagnosis of pSLE. EC4d could provide a useful biomarker for disease activity monitoring.

Mesenchymal stem cell transplantation in systemic lupus erythematous, a mesenchymal stem cell disorder

Systemic lupus erythematosus (SLE) is a chronic autoimmune and inflammatory disorder with involvement of several organs and systems such as the kidney, lung, brain and the hematopoietic system. As the most prevailing organ manifestation, lupus nephritis is the major cause of mortality and morbidity in SLE patients. The most classically and widely administered immunosuppressive medications, namely corticosteroids and cyclophosphamide, have eventuated in a remarkable amelioration in disease complications over the last few years and reduced the progression to end-stage multiorgan failure. Mesenchymal stem cells (MSCs) are considered as non-hematopoietic and multipotential progenitor cells, which are able to differentiate into multiple cell lineages such as chondrocytes, osteoblasts, myoblasts, endothelial cells, adipocytes, neuron-like cells, hepatocytes and cardiomyocytes. MSCs from SLE patients have demonstrated defects such as aberrant cytokine production. Moreover, impaired phenotype, growth and immunomodulatory functions of MSCs from patients with SLE in comparison to healthy controls have been reported. Therefore, it is hypothesized that SLE is potentially an MSC-mediated disease and, as a result, allogeneic rather than autologous MSC transplantation can be argued to be a potentially advantageous therapy for patients with SLE. On the other hand, the MSC senescence phenomenon may meet the current therapeutic approaches with challenges and demand more attention. Here, we discuss MSC transplantations to date in animal models and humans and focus on the MSC senescence complications in SLE patients.

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.

Emerging technologies in autoantibody testing for rheumatic diseases

Testing for the presence of antinuclear antibodies (ANAs) is a key step in the diagnosis of systemic lupus erythematosus (SLE) and other systemic autoimmune rheumatic diseases (SARD). The standard slide-based indirect immunofluorescence (IIF) test is widely used, but is limited by a relative lack of specificity for SLE and not all SARD-ANAs are detected. Alternative immunoassays that might offer enhanced diagnostic and prognostic information have evolved, and some of these have entered clinical practice. This review summarizes the current state of ANA testing and multiplex techniques for detecting other autoantibodies, the possibility of point-of-care testing, and approaches for applications in early disease stages.

Clinical associations of the positive anti Ro52 without Ro60 autoantibodies: undifferentiated connective tissue diseases

Aims

Autoantibodies targeting Ro52 and Ro60 antigens are historically reported as anti SSA/Ro. In general anti SSA/Ro results are either anti Ro52+Ro60+ or anti Ro52−Ro60+ antibodies. Anti Ro52 without anti Ro60 (Ro52+ Ro60−) antibodies are often not reported routinely. This study intends to review the potential significance of these autoantibodies in the management of connective tissue diseases.

Method

A retrospective survey of Ro52+Ro60− was carried out as part of the service evaluation of extractable nuclear antigen antibodies (ENA) reporting from the immunology laboratory, the NHS Greater Glasgow and Clyde (GGC), UK. The clinical documents and laboratory results of 97 patients with Ro52+Ro60− and 100 patients with Ro52+Ro60+ were reviewed.

Results

Seventy-one patients (73%) with anti Ro52+Ro60− antibodies have been diagnosed with autoimmune conditions including undifferentiated connective tissue diseases (n=14, 14%), systemic lupus erythematosus (n=10, 10%), Sjögren’s syndrome (n=10, 10%) and rheumatoid arthritis (n=13, 13%). Twenty-three patients (24%) with anti Ro52+Ro60− antibodies have no autoimmune features but were found to have significant clinical conditions including malignancies. In contrast, 87 patients (87%) with anti Ro52+Ro60+ antibodies have autoimmune conditions including Sjögren’s syndrome (n=34, 34%), systemic lupus erythematosus (SLE; n=23, 23%), undifferentiated connective tissue diseases (n=12, 12%) and rheumatoid arthritis (n=6, 6%).

Conclusion

Anti Ro52 without anti Ro60 (Ro52+Ro60−) antibodies should be reported. In the majority of patients these autoantibodies were associated with various autoimmune diseases. Anti Ro52+Ro60− antibodies were also found in patients with significant clinical conditions including malignancies even though there was no suggestion of autoimmunity at the time of testing.

Demographic associations for autoantibodies in disease-free individuals of a European population

The presence of autoantibodies usually precedes autoimmune disease, but is sometimes considered an incidental finding with no clinical relevance. The prevalence of immune-mediated diseases was studied in a group of individuals from the Estonian Genome Project (n = 51,862), and 6 clinically significant autoantibodies were detected in a subgroup of 994 (auto)immune-mediated disease-free individuals. The overall prevalence of individuals with immune-mediated diseases in the primary cohort was 30.1%. Similarly, 23.6% of the participants in the disease-free subgroup were seropositive for at least one autoantibody. Several phenotypic parameters were associated with autoantibodies. The results suggest that (i) immune-mediated diseases are diagnosed in nearly one-third of a random European population, (ii) 6 common autoantibodies are detectable in almost one-third of individuals without diagnosed autoimmune diseases, (iii) tissue non-specific autoantibodies, especially at high levels, may reflect preclinical disease in symptom-free individuals, and (iv) the incidental positivity of anti-TPO in men with positive familial anamnesis of maternal autoimmune disease deserves further medical attention. These results encourage physicians to evaluate autoantibodies in addition to treating a variety of patient health complaints to detect autoimmune-mediated disease early.

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

Background

Antinuclear antibody (ANA)5 testing is routinely performed during evaluation of patients with a suspected connective tissue disease (CTD), yet the question of which method is most appropriate remains controversial. The purpose of this study was to evaluate the clinical utility of ANA testing by an enzyme immunoassay (EIA), an immunofluorescence assay (IFA), and a multiplex immunoassay (MIA) in a routine laboratory population.

Methods

Samples (n = 1000) were collected from specimens submitted for ANA testing by EIA (Bio-Rad). All samples were subsequently analyzed by IFA (Zeus) and MIA (Bio-Rad). The sample cohort was weighted to represent the routine testing population. Diagnostic information was obtained by chart review.

Results

For the diagnosis of a CTD, ROC curve analysis demonstrated no significant differences between IFA (area under the curve 0.81) and EIA (0.84) (P = 0.25), with overlay of a single point for the MIA. When normalized to a specificity of approximately 90%, the sensitivities of the MIA, EIA, and IFA were 67%, 67%, and 56%, respectively. By varying the clinical cutoff, the IFA could achieve the highest sensitivity of 94%; however, the corresponding specificity was only 43%. In contrast, a strongly positive EIA had a specificity of 97%, although, at this cutoff, the sensitivity was only 40%.

Conclusions

Although the overall diagnostic performance of the IFA, EIA, and MIA were not statistically different, the clinical sensitivity and specificity varied dramatically based on the positive/negative cutoff. Knowledge about the performance characteristics of each method will significantly aid in the interpretation of ANA testing.

Comparison of two extractable nuclear antigen testing algorithms: ALBIA versus ELISA/line immunoassay

Extractable nuclear antigen (ENA) antibody testing is often requested in patients with suspected connective tissue diseases. Most laboratories in Australia use a two step process involving a high sensitivity screening assay followed by a high specificity confirmation test. Multiplexing technology with Addressable Laser Bead Immunoassay (e.g., FIDIS) offers simultaneous detection of multiple antibody specificities, allowing a single step screening and confirmation. We compared our current diagnostic laboratory testing algorithm [Organtec ELISA screen / Euroimmun line immunoassay (LIA) confirmation] and the FIDIS Connective Profile. A total of 529 samples (443 consecutive+86 known autoantibody positivity) were run through both algorithms, and 479 samples (90.5%) were concordant. The same autoantibody profile was detected in 100 samples (18.9%) and 379 were concordant negative samples (71.6%). The 50 discordant samples (9.5%) were subdivided into 'likely FIDIS or current method correct' or 'unresolved' based on ancillary data. 'Unresolved' samples (n = 25) were subclassified into 'potentially' versus 'potentially not' clinically significant based on the change to clinical interpretation. Only nine samples (1.7%) were deemed to be 'potentially clinically significant'. Overall, we found that the FIDIS Connective Profile ENA kit is non-inferior to the current ELISA screen/LIA characterisation. Reagent and capital costs may be limiting factors in using the FIDIS, but potential benefits include a single step analysis and simultaneous detection of dsDNA antibodies.

Single-cell antibody nanowells: a novel technology in detecting anti-SSA/Ro60- and anti-SSB/La autoantibody-producing cells in peripheral blood of rheumatic disease patients

Background

Anti-SSA/Ro60 and anti-SSB/La are essential serological biomarkers for rheumatic diseases, specifically Sjögren’s syndrome (SS) and systemic lupus erythematosus (SLE). Currently, laboratory detection technology and platforms are designed with an emphasis on high-throughput methodology; therefore, the relationship of sensitivity with specificity remains a significant area for improvement. In this study, we used single-cell antibody nanowells (SCAN) technology to directly profile individual B cells producing antibodies against specific autoantigens such as SSA/Ro60 and SSB/La.

Methods

Peripheral blood mononuclear cells were isolated using Ficoll gradient. Fluorescently labeled cells were added to fabricated nanowells and imaged using a high-speed epifluorescence microscope. The microengraving process was conducted using printed slides coated with immunoglobulins. Printed slides were hybridized with fluorescence-conjugated immunoglobulin G (IgG), SSA/Ro60, and SSB/La antigens. Microarray spots were analyzed for nanowells with single live B cells that produced antigen-specific autoantibodies.

Results

Our results indicate that SCAN can simultaneously detect high frequencies of anti-SSA/Ro60 and anti-SSB/La with a specific IgG isotype in peripheral blood mononuclear cells of patients, as well as measure their individual secretion levels. The data showed that patients with SS and SLE exhibited higher frequency and greater concentration of anti-SSA/Ro60- and anti-SSB/La-producing B cells in the IgG isotype. Furthermore, individual B cells of patients produced higher levels of IgG-specific anti-SSA/Ro60 autoantibody, but not IgG-specific anti-SSB/La autoantibody, compared with healthy control subjects.

Conclusions

These results support the application of SCAN as a robust multiparametric analytical bioassay that can directly measure secretion of autoantibody and accurately report antigen-specific, autoantibody-producing cells.

Detection of autoantibodies using chemiluminescence technologies

Context: Although autoantibody detection methods such as indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assays (ELISAs) have been available for many years and are still in use the innovation of fast, fully automated instruments using chemiluminescence technology in recent years has led to rapid adoption in autoimmune disease diagnostics. In 2009, BIO-FLASH, a fully automated, random access chemiluminescent analyzer, was introduced, proceeded by the development of the QUANTA Flash chemiluminescent immunoassays (CIA) for autoimmune diagnostics.

Objective: To summarize the evolution of CIAs for the detection of autoantibodies and to review their performance characteristics.

Methods: Pubmed was screened for publications evaluating novel QUANTA Flash assays and how they compare to traditional methods for the detection of autoantibodies. In addition, comparative studies presented at scientific meetings were summarized.

Results: Several studies were identified that compared the novel CIAs with conventional methods for autoantibody detection. The agreements ranged from moderate to excellent depending on the assay. The studies show how the CIA technology has enhanced the analytical and clinical performance characteristics of many autoantibody assays supporting both diagnosis and follow-up testing.

Conclusion: CIA has started to improve the diagnostic testing of autoantibodies as an aid in the diagnosis of a broad range of autoimmune diseases.

Autoantibodies to Dense Fine Speckles in Pediatric Diseases and Controls

OBJECTIVE

Autoantibodies to the dense fine speckled 70 kDa antigen (DFS70) are reported to be more common in individuals who do not have an antinuclear antibody (ANA)-associated rheumatic disease (AARD) than in patients with AARD. The frequency of anti-DFS70 antibodies has been thoroughly studied in adult but not in pediatric populations. The primary objective of this observational study was to determine the frequency of anti-DFS70 in pediatric AARD and reference cohorts.

METHODS

Sera from 743 children with AARD and related conditions, and 345 samples from reference cohorts (healthy children and those being investigated for AARD) were studied for anti-DFS70 autoantibodies as measured by a chemiluminescence immunoassay. A de-identified administrative database was used to retrieve demographic, serologic, and clinical data.

RESULTS

Anti-DFS70 antibodies were seen in 2.1% of healthy children and in 4.5% of sera from pediatric individuals referred for ANA testing. The frequency of anti-DFS70 was highest in juvenile localized scleroderma (LS; 4/29, 13.8%), juvenile dermatomyositis (JDM; 2/11, 18.2%), childhood systemic lupus erythematosus (cSLE; 19/331, 5.7%), diffuse cutaneous systemic sclerosis (1/22, 4.5%), celiac disease (2/49, 4.1%), and juvenile idiopathic arthritis (JIA; 5/202, 2.5%). Of note, anti-DFS70 antibodies were observed in 3/26 children (11.5%) with uveitis and JIA-associated uveitis.

CONCLUSION

The frequency of anti-DFS70 autoantibodies in healthy pediatric subjects is within the lower range of that reported in adults. Anti-DFS70 antibodies can be found in childhood SSc and cSLE, but has a remarkably high frequency in children with LS, JDM, and uveitis.

EUROPattern Suite technology for computer-aided immunofluorescence microscopy in autoantibody diagnostics

Antinuclear autoantibodies (ANA) are highly informative biomarkers in autoimmune diagnostics. The increasing demand for effective test systems, however, has led to the development of a confusingly large variety of different platforms. One of them, the indirect immunofluorescence (IIF), is regarded as the common gold standard for ANA screening, as described in a position statement by the American College of Rheumatology in 2009. Technological solutions have been developed aimed at standardization and automation of IIF to overcome methodological limitations and subjective bias in IIF interpretation. In this review, we present the EUROPattern Suite, a system for computer-aided immunofluorescence microscopy (CAIFM) including automated acquisition of digital images and evaluation of IIF results. The system was originally designed for ANA diagnostics on human epithelial cells, but its applications have been extended with the latest system update version 1.5 to the analysis of antineutrophil cytoplasmic antibodies (ANCA) and anti-dsDNA antibodies.

Diagnostic profile on the IFA 40: HEp-20-10 - an immunofluorescence test for reliable antinuclear antibody screening

Indirect immunofluorescence assay is the recommended gold standard to test for antinuclear antibodies (ANA), which are important biomarkers for systemic rheumatic autoimmune diseases. It is internationally accepted that indirect immunofluorescence assay ANA screening is most sensitive on human epithelial (HEp-2) cells. The cells present a multitude of antigens that display distinguishable localization patterns in interphase and mitotic cells in indirect immunofluorescence analysis. Here, we present the IFA 40: HEp-20-10 test kit (Euroimmun AG, Lübeck, Germany), which is cleared for sale on the US market by the FDA. The test has been designed for qualitative and semiquantitative screening of ANA in human sera. It uses the commonly applied 1:40 cutoff dilution and the enhanced HEp-20-10 cell line for more efficient pattern recognition and has been validated in various studies and by method comparison. The IFA 40: HEp-20-10 test fulfills the essential criteria for reliable application in autoimmune diagnostics.

Cell-bound complement activation products in systemic lupus erythematosus: comparison with anti-double-stranded DNA and standard complement measurements

OBJECTIVE

To compare the performance characteristics of cell-bound complement (C4d) activation products (CBCAPS) on erythrocyte (EC4d) and B cells (BC4d) with antibodies to double-stranded DNA (anti-dsDNA) and complement C3 and C4 in systemic lupus erythematosus (SLE).

METHODS

The study enrolled 794 subjects consisting of 304 SLE and a control group consisting of 285 patients with other rheumatic diseases and 205 normal individuals. Anti-dsDNA and other autoantibodies were measured using solid-phase immunoassays while EC4d and BC4d were determined using flow cytometry. Complement proteins were determined using immunoturbidimetry. Disease activity in SLE was determined using a non-serological Systemic Lupus Erythematosus Disease Activity Index SELENA Modification. A two-tiered methodology combining CBCAPS with autoantibodies to cellular and citrullinated antigens was also developed. Statistical analyses used area under receiver operating characteristic curves and calculations of area under the curve (AUC), sensitivity and specificity.

RESULTS

AUC for EC4d (0.82±0.02) and BC4d (0.84±0.02) was higher than those yielded by C3 (0.73±0.02) and C4 (0.72±0.02) (p<0.01). AUC for CBCAPS was also higher than the AUC yielded by anti-dsDNA (0.79±0.02), but significance was only achieved for BC4d (p<0.01). The combination of EC4d and BC4d in multivariate testing methodology with anti-dsDNA and autoantibodies to cellular and citrullinated antigens yielded 80% sensitivity for SLE and specificity ranging from 70% (Sjogren's syndrome) to 92% (rheumatoid arthritis) (98% vs. normal). A higher proportion of patients with SLE with higher levels of disease activity tested positive for elevated CBCAPS, reduced complement and anti-dsDNA (p<0.03).

CONCLUSIONS

CBCAPS have higher sensitivity than standard complement and anti-dsDNA measurements, and may help with the differential diagnosis of SLE in combination with other autoantibodies.

Successful treatment of DEAP-HUS with eculizumab

BACKGROUND

Deficiency of complement factor H-related (CFHR) proteins and CFH autoantibody-positive hemolytic uremic syndrome (DEAP-HUS) represents a unique subgroup of complement-mediated atypical HUS (aHUS). Autoantibodies to the C-terminus of CFH block CFH surface recognition and mimic mutations found in the genetic form of (CFH-mediated) aHUS. CFH autoantibodies are found in 10-15 % of aHUS patients and occur--so far unexplained--almost exclusively in the background of CFHR1 or CFHR3/CFHR1 deletions.

METHODS

As a well-defined role for eculizumab in the treatment of complement-mediated aHUS is becoming established, its role in DEAP-HUS is less conspicuous, where a B-cell-depleting and immunosuppressive treatment strategy is being proposed in the literature.

RESULTS

We here show eculizumab to be safe and effective in maintaining a disease-free state, without recurrence, in a previously plasma-therapy-dependent DEAP-HUS patient, and in another patient in whom, although showing a good clinical response to plasma therapy, the therapy was hampered by allergic reactions to fresh frozen plasma and contend there is a rationale for the use of eculizumab in concert with an immunosuppressive strategy in the treatment of DEAP-HUS. Considering the high rate of early relapse, the possible coexistence and contribution of both known and unknown complement-gene mutations, the probable pathogenic role of CFHR1 as a complement alternative pathway (CAP) regulator, the experimental nature of measuring and using anti-CFH autoantibodies to guide management, and until the positive reports of immunosuppression in addition to plasma therapy are confirmed in prospective studies, we feel that a complement-directed therapy should not be neglected in DEAP-HUS. Serial CFH autoantibody titer testing may become a valuable tool to monitor treatment response, and weaning patients off eculizumab may become an option once CFH autoantibody levels are depleted.

CONCLUSIONS

A prospective study of eculizumab treatment in a larger cohort of DEAP-HUS patients is required to validate the applicability of our positive experience.

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

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

The spectrum of anti-chromatin/nucleosome autoantibodies: independent and interdependent biomarkers of disease

Autoantibodies directed to chromatin components date back to the discovery of the LE cell and the LE cell phenomenon circa 1950, and subsequent evidence that major components of that reaction were chromatin components and histones in particular. Over time, immunoassays ranging from ELISA and line immunoassays to more modern bead-based assays incorporated histone and DNA mixtures, purified histones, and purified nucleosomes leading to a more thorough understanding of the genesis and pathogenetic relationships of antibodies to chromatin components in systemic lupus erythematosus and other autoimmune conditions. More recently, interest has focussed on other components of chromatin such as high mobility group (HMG) proteins both as targets of B cell responses and pro-inflammatory mediators. This review will focus on immunoassays that utilize chromatin components, their clinical relationships, and newer evidence implicating HMG proteins and DNA neutrophil extracellular traps (NETs) as important players in systemic autoimmune rheumatic diseases.

Current state of diagnostic technologies in the autoimmunology laboratory

The methods for detecting and measuring autoantibodies have evolved markedly in recent years, encompassing three generations of analytical technologies. Many different immunoassay methods have been developed and used for research and laboratory practice purposes, from the early conventional (or monoplex) analytical methods able to detect single autoantibodies to the more recent multiplex platforms that can quantify tens of molecules. Although it has been in use for over 50 years, indirect immunofluorescence remains the standard method for research on many types of autoantibodies, due to its characteristics of diagnostic sensitivity and also to recent technological innovations which permit it a greater level of automation and standardization. The recent multiplex immunometric methods, with varying levels of automation, present characteristics of higher diagnostic accuracy, but are not yet widely diffused in autoimmunology laboratories due to the limited number of autoantibodies that are detectable, and due to the high cost of reagents and systems. Technological advancement in autoimmunology continues to evolve rapidly, and in the coming years new proteomic techniques will be able to radically change the approach to diagnostics and possibly also clinical treatment of autoimmune diseases. The scope of this review is to update the state of the art of technologies and methods for the measurement of autoantibodies, with special reference to innovations in indirect immunofluorescence and in multiple proteomic methods.

Evaluation of a multiplex ELISA for autoantibody profiling in patients with autoimmune connective tissue diseases

The performance of immunoassays for the detection of autoantibodies is of critical importance in the diagnosis and assessment of patients with autoimmune connective tissue diseases (ACTD). Our objective was to compare the features of two multiplexed assays—INNO-LIA ANA and Gennova-PictArray ENA ELISA—for measurement of multiple autoantibodies and their utility as a clinical tool in ACTD diagnosis. The antigens included SS-A/Ro (60 and 52), SSB/La, Sm, Sm/RNP, CENP-B, Jo-1, and Scl-70. Stored sera from 85 ACTD patients and 80 controls consisting of patients with vasculitis, rheumatoid arthritis and infectious diseases, as well as healthy subjects were analyzed jointly with clinical and laboratory data. Agreement between the two methods varied between 58 and 99% (Cohen's kappa: 0.21–0.71) mostly for SSA and SSB. The frequency of specific autoantibodies measured using the two methods was more variable for SSA, SSB, and RNP/Sm. There were a higher number of ambiguous results when using INNO-LIA. The optimized cut-off values of the Gennova-PictArray resulted in over 99% specificities in samples obtained from the control group. Sensitivity patterns were more accurate in Gennova-PictArray than in INNO-LIA, as suggested in previously reported studies. A third method could be applied to determine which of the two methods is more accurate.

Serology of Lupus Erythematosus: Correlation between Immunopathological Features and Clinical Aspects

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the aberrant production of a broad and heterogenous group of autoantibodies. Even though the presence of autoantibodies in SLE has been known, for more than 60 years, still nowadays a great effort is being made to understand the pathogenetic, diagnostic, and prognostic meaning of such autoantibodies. Antibodies to ds-DNA are useful for the diagnosis of SLE, to monitor the disease activity, and correlate with renal and central nervous involvements. Anti-Sm antibodies are highly specific for SLE. Anti-nucleosome antibodies are an excellent marker for SLE and good predictors of flares in quiescent lupus. Anti-histone antibodies characterize drug-induced lupus, while anti-SSA/Ro and anti-SSB/La antibodies are associated with neonatal lupus erythematosus and photosensitivity. Anti-ribosomal P antibodies play a role in neuropsychiatric lupus, but their association with clinical manifestations is still unclear. Anti-phospholipid antibodies are associated with the anti-phospholipid syndrome, cerebral vascular disease, and neuropsychiatric lupus. Anti-C1q antibodies amplify glomerular injury, and the elevation of their titers may predict renal flares. Anti-RNP antibodies are a marker of Sharp's syndrome but can be found in SLE as well. Anti-PCNA antibodies are present in 5–10% of SLE patients especially those with arthritis and hypocomplementemia.

Highlights on novel technologies for the detection of antibodies to Ro60, Ro52, and SS-B

OBJECTIVE

We aimed to compare a chemiluminescent immunoassay (CIA, QUANTA Flash) on BIO-FLASH with a multiplex flow immunoassay (MFI) on BioPlex 2200 for the detection of antibodies to Ro60, Ro52, and SS-B.

METHODS

The study included 241 samples, from patients suffering from systemic autoimmune diseases (n = 108) as well as disease controls (n = 133). All samples were tested for anti-Ro52, anti-Ro60, and anti-SS-B (La) antibodies on QUANTA Flash (INOVA Diagnostics, San Diego, USA) and BioPlex 2200 (Bio-Rad Laboratories Inc., Hercules, USA). Discrepant samples were tested by two independent methods: BlueDot/ANA and QUANTRIX Microarray (both D-tek, Belgium).

RESULTS

The overall qualitative agreements were 95.4% (95% confidence interval, CI 92.0-97.7%) for anti-Ro52, 98.8% (95% CI 96.4-99.7%) for anti-Ro60, and 91.7% (95% CI 87.5-94.9%) for anti-SS-B antibodies. There were 34 discrepant samples among all assays (20 anti-SS-B, 11 anti-Ro52, 3 anti-Ro60). 30/33 of retested samples (by D-tek dot blot) agreed with the QUANTA Flash results. Similar findings were obtained with QUANTRIX Microarray kit.

CONCLUSION

QUANTA Flash and BioPlex 2200 show good qualitative agreement. The clinical performances were similar for anti-Ro52 and anti-Ro60 autoantibodies while differences were observed for anti-SS-B (La) antibodies.

Standardization of autoantibody testing: a paradigm for serology in rheumatic diseases

Autoantibody measurement is an excellent tool to confirm the diagnosis of rheumatic autoimmune diseases. Hence, reliability and harmonization of autoantibody testing are essential, but these issues are still a matter of debate. Intrinsic variability in analytes and reagents as well as heterogeneity of the techniques are the main reasons for discrepancies in inter-laboratory variations and reporting of test results. This lack of reliability might be responsible for wrong or missed diagnoses, as well as additional costs due to assay repetition, unnecessary use of confirmatory tests and/or consequent diagnostic investigations. To overcome such issues, the standardization of autoantibody testing requires efforts on all aspects of the assays, including the definition of the analyte, the pre-analytical stages, the calibration method and the reporting of results. As part of such efforts, the availability of suitable reference materials for calibration and quality control would enable the development of a reliable reference system. Strong-positive sera from patients have been used as reference materials in most of the autoantibody assays for rheumatic diseases; however, antigen-affinity-purified immunoglobulin fractions or in some cases reliable monoclonal antibody preparations offer more adequate tools for standardization. Systematic assessments of reference materials are currently underway, and preliminary results appear to be encouraging.

The association among leukocyte apoptosis, autoantibodies and disease severity in systemic lupus erythematosus

Background

Both apoptosis and autoantibodies are important factors associated with disease activity in the pathogenesis of systemic lupus erythematosus (SLE). This study tested the hypothesis that increased leukocyte apoptosis is associated with elevated levels of autoantibodies and the disease activity of SLE.

Methods

Leukocyte apoptosis was determined by flow cytometry, including annexin V, APO2.7, and 7-amino-actinomycin D (7-AAD) on each subtype of leukocyte in 23 patients with SLE. Leukocyte apoptosis was also evaluated in nine patients with Sjogren’s syndrome (SJS) and in 20 volunteer subjects. Titers of common autoantibodies and the disease activity index (SLEDAI-2 k) of the SLE patients were also determined.

Results

Except for annexin V and APO 2.7 of monocytes and late apoptosis (annexin V + 7-ADD) of lymphocytes, apoptosis in the total and in subsets of leukocytes were significantly higher in SLE patients than in controls (all p < 0.05, post hoc analysis). The mean percentage of late apoptosis of leukocytes (annexin V + 7-AAD) positively correlated with levels of anti-Ro52/60 (r = 0.513, p < 0.01), anti-La (r = 0.439, p = 0.04), and anti-Mi-2 (r = 0.492, p = 0.02), and inversely correlated with both C3 and C4 levels, although not statistically significant. The percentage of APO2.7 of CD19+ cells positively correlated with SLEDAI-2 K score (p = 0.01).

Conclusions

Leukocyte apoptosis is significantly higher in patients with SLE and correlates well with the levels of several autoantibodies. The APO2.7 of B-lymphocyte (CD19+) cells positively correlates with the disease activity of SLE.

Comparison of autoantibody specificities between traditional and bead-based assays in a large, diverse collection of patients with systemic lupus erythematosus and family members

OBJECTIVE

Replacement of standard immunofluorescence methods with bead-based assays for antinuclear antibody (ANA) testing is a new clinical option. The aim of this study was to evaluate a large, multiethnic cohort of patients with systemic lupus erythematosus (SLE), blood relatives, and unaffected control individuals for familial aggregation and subset clustering of autoantibodies by high-throughput serum screening technology and traditional methods.

METHODS

Serum samples (1,540 SLE patients, 1,154 unaffected relatives, and 906 healthy, population-based controls) were analyzed for SLE autoantibodies using a bead-based assay, indirect immunofluorescence (IIF), and immunodiffusion. Autoantibody prevalence, sensitivity for disease detection, clustering of autoantibodies, and associations between newer methods and standard immunodiffusion results were evaluated.

RESULTS

The frequencies of ANAs in the sera from African American, Hispanic, and European American patients with SLE were 89%, 73%, and 67%, respectively, by BioPlex 2200 bead-based assay and 94%, 84%, and 86%, respectively, by IIF. When comparing the serum prevalence of 60-kd Ro, La, Sm, nuclear RNP A, and ribosomal P autoantibodies across assays, the sensitivity of detection ranged from 0.92 to 0.83 and the specificity ranged from 0.90 to 0.79. Autoantibody cluster analysis showed associations of autoantibody specificities in 3 subsets: 1) 60 kd Ro, 52-kd Ro, and La, 2) spliceosomal proteins, and 3) double-stranded DNA (dsDNA), chromatin, and ribosomal P. Familial aggregation of Sm/RNP, ribosomal P, and 60-kd Ro in SLE patient sibling pairs was observed (P ≤ 0.004). Simplex-pedigree SLE patients had a greater prevalence of dsDNA (P = 0.0003) and chromatin (P = 0.005) autoantibodies compared to patients with a multiplex SLE pedigree.

CONCLUSION

The frequencies of ANAs detected by a bead-based assay are lower than those detected by IIF in European American patients with SLE. These assays have strong positive predictive values across ethnic groups, provide useful information for clinical care, and provide unique insights into familial aggregation and autoantibody clustering.

Automated indirect immunofluorescence evaluation of antinuclear autoantibodies on HEp-2 cells

Indirect immunofluorescence (IIF) on human epithelial (HEp-2) cells is considered as the gold standard screening method for the detection of antinuclear autoantibodies (ANA). However, in terms of automation and standardization, it has not been able to keep pace with most other analytical techniques used in diagnostic laboratories. Although there are already some automation solutions for IIF incubation in the market, the automation of result evaluation is still in its infancy. Therefore, the EUROPattern Suite has been developed as a comprehensive automated processing and interpretation system for standardized and efficient ANA detection by HEp-2 cell-based IIF. In this study, the automated pattern recognition was compared to conventional visual interpretation in a total of 351 sera. In the discrimination of positive from negative samples, concordant results between visual and automated evaluation were obtained for 349 sera (99.4%, kappa = 0.984). The system missed out none of the 272 antibody-positive samples and identified 77 out of 79 visually negative samples (analytical sensitivity/specificity: 100%/97.5%). Moreover, 94.0% of all main antibody patterns were recognized correctly by the software. Owing to its performance characteristics, EUROPattern enables fast, objective, and economic IIF ANA analysis and has the potential to reduce intra- and interlaboratory variability.

Multiple Autoantibodies Display Association with Lymphopenia, Proteinuria, and Cellular Casts in a Large, Ethnically Diverse SLE Patient Cohort

Purpose. This study evaluates high-throughput autoantibody screening and determines associated systemic lupus erythematosus (SLE) clinical features in a large lupus cohort. Methods. Clinical and demographic information, along with serum samples, were obtained from each SLE study participant after appropriate informed consent. Serum samples were screened for 10 distinct SLE autoantibody specificities and examined for association with SLE ACR criteria and subcriteria using conditional logistic regression analysis. Results. In European-American SLE patients, autoantibodies against 52 kD Ro and RNP 68 are independently enriched in patients with lymphopenia, anti-La, and anti-ribosomal P are increased in patients with malar rash, and anti-dsDNA and anti-Sm are enriched in patients with proteinuria. In African-American SLE patients, cellular casts associate with autoantibodies against dsDNA, Sm, and Sm/nRNP. Conclusion. Using a high-throughput, bead-based method of autoantibody detection, anti-dsDNA is significantly enriched in patienets with SLE ACR renal criteria as has been previously described. However, lymphopenia is associated with several distinct autoantibody specificities. These findings offer meaningful information to allow clinicians and clinical investigators to understand which autoantibodies correlate with select SLE clinical manifestations across common racial groups using this novel methodology which is expanding in clinical use.

Yeast surface display-based microfluidic immunoassay

In this paper, we present a new microfluidic immunoassay platform, which is based on the synergistic combination of the yeast surface display (YSD) technique and the microfluidic technology. Utilizing the YSD technique, antigens specific to the target antibody are displayed on the surface of engineered yeast cells with intracellular fluorescent proteins. The displayed antigens are then used for the detection of the target antibody, with the yeast cells as fluorescent labels. Multiplex immunoassay can be readily realized by using yeast cells expressing different intracellular fluorescent proteins to display different antigens. The implementation of this YSD-based immunoassay on the microfluidic platform eliminates the need for the bulky, complex and expensive flow cytometer. To improve the detection sensitivity and to eliminate the need for pumping, a functionalized micro pillar array (MPA) is incorporated in the microfluidic chip, resulting in a detection limit of 5 ng/mL (or 1 ng in terms of amount) and enhanced compatibility with practical applications such as clinical biopsy. This new platform has a high potential to be integrated into microfluidic detection systems to enable portable diagnostics in the future.

Autoantibody detection by direct counting of antigen-displayed yeast cells

In this study, we report a new immunoassay platform based on yeast surface display technology for detection of autoantibodies involved in autoimmune diseases, e.g., systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS). The autoantigens of Ro52/SSA epitope and SmD were chosen to be displayed on the yeast surface with their respective antibodies as the analytes. By using magnetic beads modified with protein G, yeast cells bound with specific target antibody can be captured. The amount of analytes could be determined by counting the number of fluorescent yeast cells captured in a magnetic field. The platform showed promising results in the detection of SLE autoantibodies with high sensitivity and multiplex detection capability over the traditional approaches.

Multiplexed quantification of 63 proteins in human urine by multiple reaction monitoring-based mass spectrometry for discovery of potential bladder cancer biomarkers

Three common urological diseases are bladder cancer, urinary tract infection, and hematuria. Seventeen bladder cancer biomarkers were previously discovered using iTRAQ - these findings were verified by MRM-MS in this current study. Urine samples from 156 patients with hernia (n=57, control), bladder cancer (n=76), or urinary tract infection/hematuria (n=23) were collected and subjected to multiplexed LC-MRM/MS to determine the concentrations of 63 proteins that are normally considered to be plasma proteins, but which include proteins found in our earlier iTRAQ study. Sixty-five stable isotope-labeled standard proteotypic peptides were used as internal standards for 63 targeted proteins. Twelve proteins showed higher concentrations in the bladder cancer group than in the hernia and the urinary tract infection/hematuria groups, and thus represent potential urinary biomarkers for detection of bladder cancer. Prothrombin had the highest AUC (0.796), with 71.1% sensitivity and 75.0% specificity for differentiating bladder cancer (n=76) from non-cancerous (n=80) patients. The multiplexed MRM-MS data was used to generate a six-peptide marker panel. This six-peptide panel (afamin, adiponectin, complement C4 gamma chain, apolipoprotein A-II precursor, ceruloplasmin, and prothrombin) can discriminate bladder cancer subjects from non-cancerous subjects with an AUC of 0.814, with a 76.3% positive predictive value, and a 77.5% negative predictive value. This article is part of a Special Section entitled: Understanding genome regulation and genetic diversity by mass spectrometry.

Measurement of autoantibodies in pediatric-onset systemic lupus erythematosus and their relationship with disease-associated manifestations

OBJECTIVE

To evaluate an autoantibody profile in pediatric-onset systemic lupus erythematosus (SLE) patients to determine clinical and statistical associations with disease-associated manifestations.

METHODS

Sera from 53 SLE patients and 22 healthy individuals were collected. Antibodies to C1q, histone, chromatin, ribosomal P, dsDNA, and high-avidity dsDNA were measured by enzyme-linked immunosorbent assays. Patient records were evaluated for clinical and laboratory associations.

RESULTS

The most prevalent autoantibodies found in the SLE cohort were anti-C1q antibodies (n = 32, 60%), which correlated significantly with proteinuria and decreased complement levels (P < 0.05). Anti-C1q and antihistone antibodies were significantly elevated in patients with class III/IV nephritis compared with class I/II/V nephritis (P = 0.041). SLE patients with active nephritis at the time of sample collection demonstrated significantly elevated levels of anti-C1q antibodies compared with those without active nephritis, also exhibiting 100% sensitivity for active nephritis, proteinuria, and urinary casts. Antibodies to C1q, dsDNA, histone, and chromatin were significantly elevated in patients with active disease (P < 0.01). Chart-documented anti-dsDNA antibodies were positive in 28 SLE patients, INOVA anti-dsDNA antibodies in 25 patients, and high-avidity anti-dsDNA antibodies in 8 patients. Antihistone correlated significantly with leukopenia and hemolytic anemia (P < 0.05).

CONCLUSIONS

This study indicates the importance of measuring anti-C1q antibodies in pediatric-onset SLE patients because elevated anti-C1q antibodies may be more indicative of renal disease activity, showing significant correlation with proteinuria, urinary casts, and active nephritis. Antibodies to C1q, histone, chromatin, and dsDNA exhibited the strongest association with clinical features, indicating the importance of measuring all of these antibodies in pediatric-onset SLE patients.

Comparison of indirect immunofluorescence and multiplex antinuclear antibody screening in systemic sclerosis

Indirect immunofluorescence antinuclear antibodies (IIF-ANA) are detected in approximately 90% of scleroderma patients, and the staining pattern correlates with scleroderma-specific antibody subsets. Solid-phase ANA assays that are dependent on multiplex bead technology (MULTIPLEX-ANA) are replacing immunofluorescence in many commercial labs; however, performance of these assays has not been compared to IIF-ANA in scleroderma. The purpose of this study was to evaluate whether a proportion of scleroderma patients have negative testing on MULTIPLEX-ANA assays and demonstrate whether negative MULTIPLEX-ANA is associated with particular scleroderma-specific autoantibodies. A retrospective chart review was completed on all 238 scleroderma patients evaluated in the Georgetown scleroderma clinic between June 1, 2008 and May 31, 2009. Autoantibody results, demographics, and scleroderma features were collected. Data were analyzed using unpaired t test and Mann-Whitney U test for continuous variables, and Fisher's exact test for dichotomous variables. Simple kappa coefficient was used to measure the level of agreement between MULTIPLEX-ANA and IIF-ANA results. Two-tailed p values <0.05 were considered significant. MULTIPLEX-ANA testing was available in 57 patients and only 29 (51%) tested positive. In contrast, IIF-ANA was positive in 91% of these patients. Using simple kappa coefficient, there was a good agreement between the MULTIPLEX-ANA, and presence of Scl70, RNP, and centromere antibodies (0.76; 95% CI 0.59, 0.92), but there was no agreement between MULTIPLEX-ANA and presence of other IIF-ANA patterns including nucleolar ANA (-0.40; 95% CI -0.64, -0.16). Because RNA polymerase III and nucleolar antibodies are seen in 43% of the entire scleroderma population, we are concerned that these false-negative tests could result in delays in referral and diagnosis. Until the MULTIPLEX-ANA assays can be modified to include the antigens for RNA polymerase III and the nucleolar ANA subsets, IIF-ANA remains the recommended screening test for ANA in suspected scleroderma.