Detection of autoantibodies using chemiluminescence technologies

Diagnostic Accuracy of IgA Anti-Transglutaminase Assessed by Chemiluminescence: A Systematic Review and Meta-Analysis

A new chemiluminescence immunoassay method (CLIA) for detecting IgA anti-transglutaminase (atTG IgA) in celiac disease (CD) has prompted inquiries into its diagnostic performance. We conducted a systematic review and meta-analysis comparing CLIA with traditional enzyme-linked immunosorbent assay (ELISA) and fluorescence enzyme immunoassay (FEIA). We searched PubMed, Medline, and Embase databases up to March 2024. The diagnostic references were intestinal biopsy and ESPGHAN guidelines. We calculated the sensitivity and specificity of atTG IgA assessed by CLIA and the odds ratio (OR) between the assays. Eleven articles were eligible for the systematic review and seven for the meta-analysis. Sensitivity and specificity of atTG IgA CLIA-assay were 0.98 (95% CI, 0.95-0.99) and 0.97 (95% CI, 0.94-0.99), respectively. The sensitivity of atTG IgA antibody detection did not significantly vary across the three assay modalities examined (CLIA vs. ELISA OR: 1.08 (95% CI, 0.56-2.11; p = 0.8); CLIA vs. FEIA OR: 6.97 (95% CI, 0.60-81.03; p = 0.1). The specificity of atTG IgA assessed by FEIA was higher than for CLIA (OR 0.17 (95% CI, 0.05-0.62); p < 0.007). According to the systematic review, normalization of atTG IgA levels in CD patients following a gluten-free diet was delayed when using CLIA compared to ELISA and FEIA methods. Conflicting findings were reported on the antibody threshold to use in order to avoid biopsy confirmation.

[Obstetric Antiphospholipid Syndrome: Insights on the Diagnosis, Treatment, and Hot Issues]

Obstetric antiphospholipid syndrome (OAPS) is an autoimmune disorder associated with various pathological pregnancies, such as recurrent miscarriage, stillbirth, severe pre-eclampsia and severe placental insufficiency. The persistent presence of antiphospholipid antibodies (aPLs) is the most important laboratory characteristic of OAPS. OAPS severely affects the reproductive health of women of childbearing age in China. Reports indicate that approximately 9.6% stillbirths, 11.5% severe pre-eclampsia, and 54% recurrent miscarriages are associated with OAPS or aPLs. However, the pathogenesis of OAPS remains unclear. Previously, thrombosis at the maternal-fetal interface (MFI) was considered the main mechanism of OAPS-related pathological pregnancies. Consequently, the use of low molecular weight heparin and aspirin throughout pregnancy was recommended to improve outcomes in OAPS patient. In recent years, many studies have found that thrombosis in MFI is uncommon, but various inflammatory factors are significantly increased in the MFI of OAPS patients. Based on these findings, some clinicians have started using anti-inflammatory treatments for OAPS, which have preliminarily improved the pregnancy outcomes. Nevertheless, there is no consensus on these second-line treatments of OAPS. Another troubling issue is the clinical diagnosis of OAPS. Similar to other autoimmune diseases, there are only classification criteria for OAPS, and clinical diagnosis of OAPS depends on the clinicians' experience. The present classification criteria of OAPS were established for clinical and basic research purposes, not for patient clinical management. In clinical practice, many patients with both positive aPLs and pathological pregnancy histories do not meet the strict OAPS criteria. This has led to widespread issues of incorrect diagnosis and treatment. Timely and accurate diagnosis of OAPS is crucial for effective treatment. In this article, we reviewed the epidemiological research progress on OAPS and summarized its classification principles, including: 1) the persistent presence of aPLs in circulation; 2) manifestations of OAPS, excluding other possible causes. For the first point, accurate assessment of aPLs is crucial; for the latter, previous studies regarded only placenta-related pregnancy complications as characteristic manifestations of OAPS. However, recent studies have indicated that adverse pregnancy outcomes related to trophoblast damage, such as recurrent miscarriage and stillbirth, also need to be considered in OAPS. We also discussed several key issues in the diagnosis and treatment of OAPS. First, we addressed the definition of non-standard OAPS and offered our opinion on defining non-standard OAPS within the framework of the 2023 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) APS criteria. Then, we discussed the advantages and disadvantages of different aPL testing methods, emphasizing that harmonizing results across platforms and establishing specific reference values are keys to resolving controversies in aPL testing results. We also introduced the application of non-criteria aPLs, especially anti-phosphatidylserine/prothrombin antibody (aPS/PT) and anti-β2 glycoprotein Ⅰ domain Ⅰ antibody (aβ2GPⅠDⅠ). Additionally, we discussed aPL-based OAPS risk classification strategies. Finally, we proposed potential treatment methods for refractory OAPS. The goal is to provide a reference for the clinical management of OAPS.

Recent Advances in Aptasensors for Rapid Pesticide Residues Detection

Pesticides are applied widely to increase agricultural output and quality, however, this practice results in residual issues that not only harm the environment but also put people and animals' lives and health at risk. As a result, it is critical to find pesticide residues in a variety of sources, including crops, water supplies, and soil. Aptamers are more flexible in their synthesis and modification, have a high level of specificity, are inexpensive, and have good stability compared to conventional detection methods. They have therefore attracted a lot of interest in the industry. This study reviews the most recent aptasensor advancements in the detection of pesticide residues. Firstly, aptamers specifically binding to many pesticides are summarized. Secondly, the combination of aptasensors with colorimetric, fluorescent, surface enhanced Raman spectroscopy (SERS), resonance Light Scattering (RLS), chemiluminescence (CL), electrochemical, and electrochemiluminescence (ECL) technologies are systematically introduced, and their advantages and disadvantages are expounded. Importantly, the aptasensors for the detection of various pesticides (organochlorine, organophosphorus, neonicotinoids, carbamates, and pyrethroids) that have been developed so far are systematically analyzed and discussed. Finally, the furture prospects and challenges of the aptasensors are highlighted. It is expected to offer suggestions for the later creation of novel, highly effective and sensitive aptasensors for the detection of pesticide residues.

Anti-β2GPI-domain I antibody is associated with extra-criteria manifestations in a large prospective antiphospholipid syndrome cohort in China

BACKGROUND

Anti-β2GPI-domain I (β2GPI-DI) antibody is pathogenic in patients with antiphospholipid syndrome (APS), but its additional clinical associations and diagnostic value are controversial.

METHODS

A total of 378 patients were included, of which 119 patients diagnosed with primary APS, 50 with APS secondary to SLE (SAPS group), 209 with SLE without APS (SLE group). Serum anti-β2GPI-DI IgG was measured using chemiluminescent immunoassay. Extra-criteria manifestations were analysed, including thrombocytopenia, autoimmune haemolytic anaemia, valvular lesions, APS nephropathy and non-vascular neurological manifestations.

RESULTS

In 169 patients with APS, 55 (32.5%) were positive for anti-β2GPI-DI IgG, accounting for 77.5% of those with anti-β2GPI IgG positivity. It is shown that 96.4% of those with anti-β2GPI-DI IgG also showed triple positivity in classic antiphospholipid antibodies (aPLs). The positivity of anti-β2GPI-DI IgG was significantly associated with recurrent thrombosis before APS diagnosis (p=0.015), microvascular thrombosis (p=0.038), but not with pregnancy morbidity (PM). Notably, patients with extra-criteria manifestations showed significantly higher positivity (p=0.001) and titres (p<0.001) in anti-β2GPI-DI IgG, especially for thrombocytopenia and APS nephropathy. In multivariable analysis, anti-β2GPI-DI IgG positivity (OR 2.94, 95% CI 1.29 to 6.70), secondary APS, arterial hypertension and Coombs' test positivity independently predicted extra-criteria manifestations (C-index 0.83, 95% CI 0.77 to 0.90). After a median follow-up of 25 months, patients with anti-β2GPI-DI IgG also showed a tendency of more extra-criteria events, but not thrombotic events. Anti-β2GPI-DI was positive among 8.1% of the SLE controls, and showed high specificity (91.9%) in diagnosing SAPS among patients with SLE as compared with classic aPLs.

CONCLUSION

Anti-β2GPI-DI IgG was associated with extra-criteria manifestations in patients with APS. Further studies are warranted to validate its predictive values and potential role in daily practice.

Anti-Proteinase 3 Antibodies as a Biomarker for Ulcerative Colitis and Primary Sclerosing Cholangitis in Children

OBJECTIVES

Anti-neutrophil cytoplasmic antibody (ANCA) directed against proteinase 3 (PR3) is a marker for granulomatosis with polyangiitis, but is also found in patients with inflammatory bowel disease (IBD), mainly ulcerative colitis (UC). The aim of our study was to investigate ANCA and PR3-ANCA in paediatric IBD.

METHODS

We tested 326 paediatric IBD patients and 164 controls for anti-Saccharomyces cerevisiae antibodies (ASCA), ANCA (indirect immunofluorescence, IIF) and PR3-ANCA (chemiluminescence immunoassay). We applied the Paris classification for paediatric IBD and documented liver manifestations such as primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH).

RESULTS

We found PR3-ANCA in 49/121 (40%) of UC, 20/187 (11%) of Crohn disease (CD) and 2/18 (11%) of IBD-unclassified (IBD-U) patients but in none of the controls. 54% UC and 12% CD patients were positive for ANCA (IIF). PR3-ANCA positive UC patients were characterised by more extensive disease (P = .070). Fourteen of 21 (67%) of UC patients with backwash ileitis were anti-PR3 ANCA-positive (P = .011). We diagnosed PSC or PSC/AIH in 19 UC and 3 IBD-U patients. Fifteen of 22 (68%) patients with PSC or PSC/AIH were anti-PR3-ANCA positive in contrast to 36 of 117 (32%) patients without PSC (P = .001). PR3-ANCA positive patients showed higher levels of gamma-glutamyl transferase, alanine transaminase and aspartate transferase (P < 0.001, 0.001, 0.006, respectively). Forty-seven percent of CD and 6% of UC patients were ASCA-IgA positive. PR3-ANCA-positive and -negative patients showed no significant differences concerning age at diagnosis, disease activity, need for drugs, and number of hospitalisations.

CONCLUSIONS

Our study provides data for PR3-ANCA as a potential serological marker for paediatric UC and PSC.

Multiparametric autoantibody analysis: a new paradigm for the diagnosis of connective tissue diseases

BACKGROUND

In patients affected by connective tissue diseases (CTDs), the identification of wide autoantibody profiles may prove useful in early diagnosis, in the evaluation of prognosis (risk stratification), and in predicting response to therapy. The aim of the present study was to evaluate the utility of multiparametric autoantibody analysis performed by a new fully automated particle-based multi-analyte technology (PMAT) digital system in a large multicenter cohort of CTD patients and controls.

METHODS

Serum samples from 787 patients with CTD (166 systemic lupus erythematosus; 133 systemic sclerosis; 279 Sjögren's syndrome; 106 idiopathic inflammatory myopathies; 103 undifferentiated CTD), 339 patients with other disorders (disease controls) (118 infectious diseases, 110 organ-specific autoimmune diseases, 111 other rheumatic diseases), and 121 healthy subjects were collected in 13 rheumatologic centers of the FIRMA group. Sera were analyzed with the Aptiva-PMAT instrument (Inova Diagnostics) for a panel of 29 autoantibodies.

RESULTS

Multiparametric logistic regression showed that enlarged antibody profiles have a higher diagnostic efficiency than that of individual antibodies or of antibodies that constitute classification criteria for a given disease and that probability of disease increases with multiple positive autoantibodies.

CONCLUSIONS

This is the first study that analyzes the clinical and diagnostic impact of autoantibody profiling in CTD. The results obtained with the new Aptiva-PMAT method may open interesting perspectives in the diagnosis and sub-classification of patients with autoimmune rheumatic diseases.

Development of a chemiluminescence immunoassay to accurately detect African swine fever virus antibodies in serum

The outbreak of African swine fever (ASF) has caused significant economic losses to animal husbandry worldwide. Currently, there is no effective vaccine or treatment available to control the disease, and therefore, efficient disease control is dependent on early detection and diagnosis of ASF virus (ASFV). In this study, a chemiluminescent immunoassay (CLIA) was developed using the ASFV protein p54 as a serum diagnostic antigen and an anti-p54 monoclonal antibody. After optimizing the working parameters of the CLIA, the sensitivity of the established CLIA was 1:128, ASFV-specific serum antibody was identified, and there was no cross-reaction with other swine virus antibodies. After testing 49 clinical serum samples, the consistency rate between the CLIA and the World Organization for Animal Health (OIE) recommended commercial kit was 100 %. Thus, this CLIA had a high degree of specificity, sensitivity, and reliability, and could be used as a rapid detection method for epidemiological investigations of ASFV infection.

Comparison of Different Test Systems for the Detection of Antiphospholipid Antibodies in a Chinese Cohort

Background

Diagnosis of antiphospholipid syndrome (APS) is based on the positivity of laboratory criteria antiphospholipid antibodies (aPLs). Test results for aPLs could be contradictory among different detection methods as well as commercial manufacturers. This study aimed to assess and compare the diagnostic and analytic performances of four commercial assays prevalently used in China.

Methods

A total of 313 patients including 100 patients diagnosed with primary APS, 52 with APS secondary to SLE, 71 with SLE, and 90 health controls were recruited. Serum IgG, IgM, and IgA for aCL, and aβ2GPI antibodies were detected with two ELISA and two CLIA systems, and test system with the best diagnostic value was explored of its correlation with key clinical features.

Results

CLIA by YHLO Biotech Co. was considered as the system with the best predictive power, where 58.55 and 57.89% of APS patients were positive for aCL or aβ2GPI for at least one antibody (IgG or IgM or IgA). Overall, CLIA showed better performance characteristics than traditional ELISA test systems.

Conclusion

CLIA was considered as a better platform for aPL detection in APS diagnosis. A combination of other detection platforms could assist in differential diagnosis as well as in identifying high-risk patients.

Fibromyalgia and Depression in Women: An 1H-NMR Metabolomic Study

Fibromyalgia is a chronic and systemic syndrome characterized by muscle, bone, and joint pain. It is a gender-specific condition with a 9:1 incidence ratio between women and men. Fibromyalgia is frequently associated with psychic disorders affecting the cognitive and emotional spheres. In the reported work, we compared 31 female fibromyalgia patients to 31 female healthy controls. They were analyzed for biochemical clinical parameters, for autoimmune markers, and were subjected to 1H-NMR metabolomics analysis. To identify a correlation between the metabolomic profile and the psychic condition, a subset of 19 fibromyalgia patients was subjected to HAM-A and HAM-D Hamilton depression tests. Multivariate statistical analysis showed the dysmetabolism of several metabolites involved in energy balance that are associated with systemic inflammatory conditions. The severity of depression worsens dysmetabolic conditions; conversely, glycine and glutamate, known for their critical role as neuromodulators, appear to be potential biomarkers of fibromyalgia and are associated with different severity depression conditions.

Advances in the diagnosis of autoimmune diseases based on citrullinated peptides/proteins

Introduction: Autoimmune diseases are still one of the hard obstacles associated with humanity. There are many exogenous and endogenous etiological factors behind autoimmune diseases, which may be combined or dispersed to stimulate the autoimmune responses. Protein citrullination represents one of these factors. Harnessing specific citrullinated proteins/peptides could early predict and/or diagnose some of the autoimmune diseases. Many generations of diagnostic tools based on citrullinated peptides with comparable specificity/sensitivity are available worldwide.Areas covered: In this review, we discuss the deimination reaction behind the citrullination of most known autoantigens targeted, different generations of diagnostic tools based on citrullinated probes with specificity/sensitivity of each as well as newly developed assays. Furthermore, the most advanced molecular analytical tools to detect the citrullinated residues in the biological fluid and their performance are also evaluated, providing new avenues to early detect autoimmune diseases with high accuracy.Expert opinion: With the current specificity/sensitivity tools available for autoimmune disease detection, emphasis must be placed on developing more advance and effective, early, rapid, and simple diagnostic devices for autoimmune disease monitoring (similar to a portable device for sugar test at home). The molecular analytical devices with dual and/or multiplexe functions should be more simplified and invested in clinical laboratories.

Anti-dsDNA, anti-nucleosome, anti-C1q, and anti-histone antibodies as markers of active lupus nephritis and systemic lupus erythematosus disease activity

Introduction

Previous studies of anti‐dsDNA, nucleosome (Nucl), histone (His), and C1q antibodies have revealed their clinical value in systemic lupus erythematosus (SLE). However, the correlation between four autoantibodies and SLE activity, lupus nephritis (LN) remains controversial, and data are insufficient on longitudinal monitoring. This study aimed at evaluating the value of these autoantibodies in active LN, and their performance on cross‐sectional evaluating and longitudinal monitoring of SLE disease activity.

Methods

Serum levels of four autoantibodies in 114 SLE patients, 219 other autoimmune disease patients (OAD), and 59 healthy controls were assayed by a quantitative immunoassay. Sera of 38 inpatients were obtained again after treatment.

Results

We found that serum levels of four autoantibodies were significantly higher in SLE than OAD patients (p < 001), active LN than non‐renal SLE patients (p < .05), and higher in SLE patients with moderate and severe disease activity than mild disease activity (p < .01). Horizontally, serum level of each autoantibody was correlated with SLE disease activity index (SLEDAI) (p < .05), and correlation coefficient of anti‐dsDNA was the highest (r = .585). For longitudinal monitoring, the decreased levels of four autoantibodies were found following treatment (p < .001). Serum level variations of these antibodies were positively correlated with variations of SLEDAI (p < .05). The correlation coefficient of anti‐Nucl was the highest (r = .629). Although the levels of C3 and C4 increased after treatment, the change was not related to the change of SLEDAI (p > .05).

Conclusions

Anti‐C1q, anti‐dsDNA, anti‐Nucl, and anti‐His perform well in diagnosing active LN and monitoring SLE disease activity. They could be indicators of active LN and SLE disease activity.

The prevalence of antiphospholipid antibodies in women with late pregnancy complications and low-risk for chromosomal abnormalities

BACKGROUND

Antiphospholipid antibodies (aPL) are known to increase the risk of obstetrical complications. However, aPL significance and prevalence in women with late-onset pregnancy complications (LO-PC) need further clarification.

OBJECTIVES

To investigate the prevalence of aPL in a cohort of women who experienced LO-PC and to compare it with a cohort of uneventful pregnancies.

METHODS

One hundred pregnant women who experienced LO-PC, had a low risk for chromosomal abnormalities, and absence of fetal abnormalities were recruited from August 2018 to August 2019. One hundred women with uneventful pregnancy were included as controls. aPL testing was performed on serum samples derived from prenatal screening test and included both criteria and "extra criteria" aPL.

RESULTS

Patients with LO-PC had significantly higher aPL prevalence when compared with controls (31/100 [31%] vs 10/100 [10%]; P < .001). More in detail, up to 26% of women with LO-PC were positive for one aPL, with an overall prevalence significantly higher than controls (26% vs 9%; P < .05). Among single aPL positivity, patients had significantly higher rate of positivity and titers of anticardiolipin IgG (10% vs 2%; mean ± standard deviation 11 ± 13 vs 4 ± 9.6 chemoluminescent unit; P < .05) and phosphatidylserine-prothrombin antibodies (aPS/PT) IgM (15% vs 6%; mean ± standard deviation 10.2 ± 21.7 vs 3.7 ± 13.7 U; P < .05). Testing for aPS/PT (IgM/IgG) alone allowed the identification of 17 patients negative for criteria aPL. aPL-positive patients had a significantly higher risk of preterm birth (34-36 + 6 weeks; 10% vs 8%; P < .012).

CONCLUSIONS

We report a high prevalence of aPL in our cohort. Testing for both criteria and "extra criteria" aPL in women with previous LO-PC could improve the diagnostic accuracy identifying women at higher risk for recurrent pregnancy complications.

Measuring ACPA in the general population or primary care: is it useful?

Rheumatoid arthritis (RA) is associated with a significant disease burden and high costs for society. Because the disease has identifiable preclinical stages, screening and prevention have become a possibility in RA. Anticitrullinated peptide antibodies (ACPAs) are arguably the most likely candidate biomarker to screen for RA. This paper reviews the evidence for the use of ACPAs as a screening test in the broader general population, to identify individuals at high risk of subsequent onset of RA. We will review the diagnostic properties of the test and its positive and negative predictive value in different settings. We will discuss how ACPA testing could effectively be integrated in a broader screening strategy for RA.

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

In 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.

A Monoclonal Antibody to M-Phase Phosphoprotein 1/Kinesin-Like Protein KIF20B

Kinesin-like protein KIF20B, originally named M-phase phosphoprotein 1 (MPP1), is a plus-end-directed kinesin-related protein that exhibits in vitro microtubule-binding and -bundling properties as well as microtubule-stimulated ATPase activity. It has been characterized as a slow molecular motor that moves toward the plus-end of microtubules. Human autoantibodies directed against KIF20B have been described in up to 25% of patients with idiopathic ataxia and less commonly in other neuropathies and autoinflammatory conditions. One of the limitations of research into the structure and function of KIF20B has been a reliable monoclonal antibody that can be used in a variety of applications. To establish a reference standard for anti-KIF20B immunoassays and facilitate studies on the role of KIF20B in developmental cell biology, we developed an IgG1 monoclonal antibody, 10C7, which reacts with the cognate KIF20B protein in Western immunoblots and in addressable laser bead immunoassays. In HEp2 cells, leptomeningeal pericytes, and transfected HEK293T cells, indirect immunofluorescence studies showed that reactivity was mainly localized to a proportion of interphase nuclei, but during metaphase, it was redistributed throughout the cytoplasm and perichromatin mass. Later in telophase/anaphase, KIF20B was localized to the stem body and midzone of the midbody. 10C7 also showed remarkable staining of a subset of cells in the cerebellum, ovary, and testis tissues. KIF20B was shown to have extensive coiled-coil domains. The monoclonal antibody, 10C7, will be of value to diagnostic laboratory scientists interested in having a reliable reference standard for anti-KIF20B immunoassays as well as cell, molecular, and developmental biology researchers.

Diagnostic laboratory tests for systemic autoimmune rheumatic diseases: unmet needs towards harmonization

Autoantibodies are helpful tools not only for the diagnosis and the classification of systemic autoimmune rheumatic diseases (SARD) but also for sub-grouping patients and/or for monitoring disease activity or specific tissue/organ damage. Consequently, the role of the diagnostic laboratory in the management of SARD is becoming more and more important. The advent of new techniques raised the need of updating and harmonizing our use/interpretation of the assays. We discuss in this opinion paper some of these issues. Indirect immunofluorescence (IIF) was originally suggested as the reference technique for anti-nuclear antibody (ANA) detection as previous solid phase assays (SPA) displayed lower sensitivity. The new available SPA are now offering better results and can represent alternative or even complementary diagnostic tools for ANA detection. The improved sensitivity of SPA technology is also changing our interpretation of the results for other types of autoantibody assays, but we need updating their calibration and new reference materials are going to be obtained in order to harmonize the assays. There is growing evidence that the identification of autoantibody combinations or profiles is helpful in improving diagnosis, patients’ subgrouping and predictivity for disease evolution in the field of SARD. We report some explanatory examples to support the idea to make the use of these autoantibody profiles more and more popular. The technological evolution of the autoimmune assays is going to change our routine diagnostic laboratory tests for SARD and validation of new algorithms is needed in order to harmonize our approach to the issue.

Autoantibodies to a novel Rpp38 (Th/To) derived B-cell epitope are specific for systemic sclerosis and associate with a distinct clinical phenotype

Objective

Detection of antinuclear antibodies and specific autoantibodies is important in the diagnosis and classification of SSc. Several proteins of the Th/To complex, including Rpp25, Rpp38 and hPop1 are the target of autoantibodies in SSc patients. However, very little is known about the epitope distribution of this autoantigen. Consequently, we screened Rpp25, Rpp38 and hPop1 for B cell epitopes and evaluated their clinical relevance.

Methods

Serum pools with (n = 2) and without (n = 1) anti-Th/To autoantibodies were generated and used for epitope discovery. Identified biomarker candidate sequences were then utilized to synthesize synthetic, biotinylated, soluble peptides. The peptides were tested to determine reactivity with sera from SSc cohorts (n = 202) and controls (n = 159) using a chemiluminescence immunoassay. Additionally, samples were also tested for antibodies to full-length recombinant Rpp25 antibodies by chemiluminescence immunoassay.

Results

Several immunodominant regions were found on the three proteins. The strongest reactivity was observed with an Rpp38 peptide (aa 229–243). Autoantibodies to the Rpp38 peptide were detected in 8/149 (5.4%) limited cutaneous SSc patients, but not in any of 159 controls (P = 0.003 by two-sided Fisher's exact probability test). Although reactivity to the novel antigenic peptide was correlated with the binding to Rpp25 (rho = 0.44; P < 0.0001), subsets of patient sera either reacted strongly with Rpp25 or with the novel Rpp38-derived peptide.

Conclusion

A novel Rpp38 epitope holds promise to increase the sensitivity in the detection of anti-Th/To autoantibodies, thus enhancing the serological diagnosis of SSc.

Reference limits for GAD65 and IA-2 autoantibodies by chemiluminescence immunoassay in Northern European adults and children

The GAD65 and IA-2 antibodies (Abs) are biomarkers of the development of type 1 diabetes mellitus (T1DM) in both children and adults. The upper reference limit for the autoantibodies made by the manufacture was established on an adult Chinese population. Here, we established upper reference limits for Northern European adults and children in accordance with the Clinical and Laboratory Standards Institute (CLSI) guidelines. Serum samples from healthy Danish children (0-18 years) and adults (18-70 years) were analysed for GAD65Ab and IA-2Ab using MAGLUMI 800 Chemiluminescence Immunoassay (CLIA). The Kruskal-Wallis test was used for evaluating differences between gender and age groups. No gender or age differences were found for neither GAD65Ab nor IA-2Ab, and a combined upper reference limit for both children and adults could be established. An upper reference limit of 5.1 IU/mL was defined for GAD65Ab and 11.5 U/mL for IA-2Ab. Our results showed a substantial discrepancy with the reference limits established by the manufacturer.

The clinical value of assays detecting antibodies against domain I of β2-glycoprotein I in the antiphospholipid syndrome

As the clinical symptoms of the antiphospholipid syndrome (APS) frequently occur irrespective of the syndrome, diagnosis predominantly depends on the laboratory assays measuring the level or function of antiphospholipid antibodies (aPLs). β2-glycoprotein I (β2GPI) is increasingly accepted as the most important target of aPLs. Anti-β2GPI antibodies constitute a heterogeneous population, but current in vivo and in vitro evidence show that especially the first domain (DI) of β2GPI contains an important pathogenic epitope. This epitope containing Glycine40-Arginine43 (G40-R43) has proven to be cryptic and only exposed when β2GPI is in its open conformation. A previous study demonstrated a highly variable exposure of the cryptic epitope in commercial anti-β2GPI assays, with implications on correct patient classification. Unexpectedly, recent unpublished data revealed impaired exposure of the pathogenic epitope in the commercially available anti-DI chemiluminescence immunoassay (CIA) assay detecting specific antibodies directed to DI. In this review we summarize the laboratory and clinical performance characteristics of the different anti-DI assays in published data and conclude with inconsistent results for both the correlation of anti-DI antibodies with clinical symptoms and the added value of anti-DI antibodies in the classification criteria of APS. Additionally, we hypothesize on possible explanations for the observed discrepancies. Finally, we highly advise manufacturers to use normal pooled plasma spiked with the monoclonal anti-DI antibodies to verify correct exposure of the cryptic epitope.

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

Introduction

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.

Methods

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).

Results

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.

Conclusion

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.

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

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

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.

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.

An ultrasensitive chemiluminescence aptasensor for thrombin detection based on iron porphyrin catalyzing luminescence desorbed from chitosan modified magnetic oxide graphene composite

In this work, an ultrasensitive chemiluminescence (CL) aptasensor was prepared for thrombin detection based on iron porphyrin catalyzing luminol - hydrogen peroxide luminescence under alkaline conditions, and iron porphyrin was desorbed from chitosan modified magnetic oxide graphene composite (CS@Fe₃O₄@GO). Firstly, CS@Fe₃O₄@GO was prepared. CS@Fe₃O₄@GO has advantages of the good biocompatibility and positively charged on its surface of CS, the large specific surface area of GO and the easy separation characteristics of Fe₃O₄. GO, Fe₃O₄ and CS@Fe₃O₄@GO were confirmed by transmission electron microscopy (TEM), scanning electron microscope (SEM), fourier transform infrared (FTIR) and X-ray powder diffraction (XRD). Then, thrombin aptamer (T-Apt) and hemin (HM, an iron porphyrin) were sequentially modified on the surface of CS@Fe₃O₄@GO to form CS@Fe₃O₄@GO@T-Apt@HM. The immobilization properties of CS@Fe₃O₄@GO to T-Apt and adsorption properties of CS@Fe₃O₄@GO@T-Apt to HM were sequentially researched through the curves of kinetics and the curves of thermodynamics. When thrombin existed in solutions, HM was desorbed from the surface of CS@Fe₃O₄@GO@T-Apt@HM owing to the strong specific recognition ability between thrombin and T-Apt, causing the changes of CL signal. Under optimized CL conditions, thrombin could be measured with the linear concentration range of 5.0×10^-15-2.5×10^-10mol/L. The detection limit was 1.5×10^-15mol/L (3δ) while the relative standard deviation (RSD) was 3.2%. Finally, the CS@Fe₃O₄@GO@T-Apt@HM-CL aptasensor was used for the determination of thrombin in practical serum samples and recoveries ranged from 95% to 103%. Those satisfactory results revealed potential application of the CS@Fe₃O₄@GO@T-Apt@HM-CL aptasensor for thrombin detection in monitoring and diagnosis of human blood diseases.

Autoantibodies to domain 1 of beta 2 glycoprotein I determined using a novel chemiluminescence immunoassay demonstrate association with thrombosis in patients with antiphospholipid syndrome

INTRODUCTION

Antibodies to the domain 1 of beta 2 glycoprotein I (β2GPI-D1) have been suggested as a risk marker for thrombosis in patients with the antiphospholipid syndrome (APS). This cross-sectional study aimed to analyze the clinical utility of a novel chemiluminescence assay for the detection of anti-β2GPI-D1 antibodies.

PATIENTS AND METHODS

Sera collected from patients with primary or secondary APS (n = 106; 72 with and 34 without history of thrombosis) and controls (n = 272) were tested for anti-β2GPI-D1 IgG by chemiluminescence assay (QUANTA Flash) and by two anti-β2GPI IgG assays (QUANTA Lite and QUANTA Flash β2GPI IgG).

RESULTS

Anti-β2GPI-D1 IgG titers were significantly higher in patients with thrombosis (P = 0.0032) than those without. At the cut-off of 20 units, which yielded a 99.5% specificity, 24 of 72 (34.9%) patients with thrombosis and four of 34 (11.8%) without thrombosis were anti-β2GPI-D1 IgG positive (odds ratio, OR = 4.0). By further optimizing the cut-off specifically for correlation with thrombosis, 20.8% of the patients with thrombosis and 2.9% of the patients without thrombosis were positive (OR = 8.7). The ORs were significantly lower for antibodies to the full-length β2GPI by either the chemiluminescence assay or ELISA. Using the anti-β2GPI chemiluminescence assay, the OR was 2.3 (recommended cut-off of 20 CU) or 4.1 (optimal cut-off 164.6 CU). Using the anti-β2GPI ELISA, the OR was 2.7 (recommended cut-off of 20 units) or 3.7 (optimal cut-off 7.6 units).

CONCLUSION

These data indicate that anti-β2GPI-D1 IgG are present more frequently and in higher titers in APS patients with thrombotic complications than in those without.The novel β2GPI-D1 chemiluminescence assay appears to be superior to full-length β2GPI assays for the risk assessment of thrombotic events in APS patients.