A WHO Reference Reagent for lupus (anti-dsDNA) antibodies: international collaborative study to evaluate a candidate preparation

Improved diagnosis of systemic lupus erythematosus with human-derived double-stranded DNA antigen

Anti-double-stranded DNA antibodies (anti-dsDNA) serve as a crucial serological indicator for systemic lupus erythematosus (SLE). Chemiluminescent immunoassay (CIA) is mainly used in clinical diagnosis of SLE, but suffers from low specificity, partially because the use of dsDNA antigens of varied sources in current CIA kits that sometimes led to controversial results. On the basis that anti-dsDNA in healthy individuals tend to selectively bind with dsDNA originating from pathogens, whereas pathogenic anti-dsDNA in SLE patients bind all forms of dsDNA, here we proposed the use of dsDNA fragment derived from human genome as antigen (synthesized via PCR using the human genomic DNA as the template). A magnetic bead-based immunofluorescence assay (IFA) was thus developed for SLE diagnosis, which exhibited improved sensitivity and specificity over CIA using the WHO reference reagent (15/174) as standard. For clinical serum sample analysis (n = 590), IFA exhibited an accuracy of 71.9% that was higher than CIA (65.3%). Crucially, the IFA results exhibited stronger correlations with the activity of SLE, renal involvement, and its prognosis. Besides the improved clinical diagnosis, the proposed IFA also holds great promise in assay standardization due to the high homogeneity of the synthetic dsDNA.

Comparison of quantitative and qualitative anti-dsDNA assays

OBJECTIVE

In evaluation of systemic lupus erythematosus (SLE), anti-double-stranded DNA antibodies (anti-dsDNA) play a significant role in diagnosis, monitoring SLE activity, and assessing prognosis. However, evaluations of the performance and limitations for recently developed methods for anti-dsDNA assessment are sparse.

METHODS

Specimens used for antinuclear antibody testing (n = 129) were evaluated for anti-dsDNA assay comparability across 4 medical centers in the United States. The methods compared were Werfen Quanta Lite dsDNA, Zeus Scientific dsDNA Enzyme Immunoassay, Bio-Rad multiplex immunoassay (MIA) dsDNA, ImmunoConcepts Crithidia, and Bio-Rad Laboratories Crithidia.

RESULTS

For quantitative anti-dsDNA measurements, Spearman's correlation coefficient was highest between Zeus and Werfen (ρ = 0.86; CI, 0.81-0.90; P < .0001). Comparison of MIA to Werfen or Zeus yielded similar results to each other (ρ = 0.58; CI, 0.44-0.68; P < .0001; and ρ = 0.59; CI, 0.46-0.69; P < .0001, respectively), but lower than the correlation between Zeus and Werfen. Positive concordance between assays ranged from 31.4% to 97.1%, and negative concordance between assays ranged from 58.5% to 100%. The detection of anti-dsDNA in those with SLE diagnosis ranged from 50.9% to 77.4% for quantitative assays and 15.1% to 24.5% for Crithidia assays.

CONCLUSION

Current quantitative anti-dsDNA assays are not interchangeable for patient follow-up. Crithidia-based assays demonstrate high negative concordance and lack positive concordance among the methods.

Recommendations for the use of anti-dsDNA autoantibodies in the diagnosis and follow-up of systemic lupus erythematosus - A proposal from an expert panel

Anti-dsDNA autoantibodies are listed as one of the classification criteria for systemic lupus erythematosus (SLE) and are relatively effective indicators for monitoring disease activity and treatment response. Therefore, clinicians rely on them to diagnose and adjust medication and treatment strategies for SLE patients. However, the use of anti-dsDNA antibodies is not free from controversy. Part of this controversy stems from the fact that anti-dsDNA antibodies are found in several disorders, besides SLE. In addition to this, anti-dsDNA antibodies are a heterogeneous group of antibodies, and their determination still lacks proper standardization. Moreover, anti-dsDNA testing specificity and diagnostic performance change depending on the population under study. These and other issues result in inconsistency and encumber the clinical use of anti-dsDNA antibodies. A panel of medical laboratory and clinical experts on SLE discussed such issues based on their clinical experience in a first meeting, establishing a series of recommendations. The proceedings of this first meeting, plus an exhaustive review of the literature, were used to compose a paper draft. The panel subsequently discussed and refined this draft in a second meeting, the result of which is this paper. This document is relevant to clinical laboratories as it guides to improving diagnosis and monitoring of SLE. Simultaneously, it will help laboratories compile more informative reports, not limited to a mere number. It is also relevant to clinical doctors who wish to better understand laboratory methods so that they can do a more efficient, better-aimed laboratory test ordering.

Nailfold Videocapillaroscopic Alterations as Markers of Microangiopathy in COVID-19 Patients

Nailfold videocapillaroscopic alterations have been described in COVID-19, but their correlations with biomarkers of inflammation, coagulation and endothelial perturbation are still unclear, and no information is available on nailfold histopathology. Nailfold videocapillaroscopy was performed on fifteen patients with COVID-19 in Milan, Italy and the signs of microangiopathy were correlated with plasma biomarkers of inflammation (C reactive protein [CRP], ferritin), coagulation (D-dimer, fibrinogen), endothelial perturbation (Von Willebrand factor [VWF]) and angiogenesis (vascular endothelial growth factor [VEGF]) along with genetic drivers of COVID-19 susceptibility. Histopathological analysis of autoptic nailfold excisions was performed on fifteen patients who died for COVID-19 in New Orleans, United States. All COVID-19 patients studied with videocapillaroscopy showed alterations rarely seen in healthy individuals consistent with microangiopathy, such as hemosiderin deposits (sign of microthrombosis and microhemorrhages) and enlarged loops (sign of endotheliopathy). The number of hemosiderin deposits correlated both with ferritin and CRP levels (r = 0.67, p = 0.008 for both) and the number of enlarged loops significantly correlated with the levels of VWF (r = 0.67, p = 0.006). Ferritin levels were higher in non-O groups, determined by the rs657152 C > A cluster, (median 619, min-max 551-3266 mg/dL) than in the O group (373, 44-581 mg/dL, p = 0.006). Nailfold histology revealed microvascular damage, i.e., mild perivascular lymphocyte and macrophage infiltration and microvascular ectasia in the dermal vessels of all cases, and microthrombi within vessels in five cases. Alterations in nailfold videocapillaroscopy and elevated biomarkers of endothelial perturbation that match histopathologic findings open new perspectives in the possibility of non-invasively demonstrating microangiopathy in COVID-19.

A comparison of the chemiluminescence immunoassay and Crithidia luciliae immunofluorescence test in detecting anti-dsDNA antibodies and assessing the activity of systemic lupus erythematosus

OBJECTIVES

This study aimed to compare the YHLO chemiluminescence immunoassay (CLIA) with the Crithidia luciliae immunofluorescence test (CLIFT) to detect anti-dsDNA antibodies and its correlation with disease activity in systemic lupus erythematosus (SLE).

METHOD

In total, 208 patients diagnosed with SLE, 110 other autoimmune patients, 70 infectious disorders patients, and 105 healthy people were enrolled in this study. Serum samples were tested using CLIA in a YHLO chemiluminescence system and CLIFT.

RESULTS

The overall agreement between YHLO CLIA and CLIFT was 76.9% (160/208), with a moderate correlation (kappa = 0.530, p < 0.001). The sensitivity of YHLO CLIA and CLIFT were 58.2% and 55.3%, respectively. The specificity of YHLO CLIA and CLIFT were 95.1% and 99.3%, respectively. The sensitivity of YHLO CLIA was increased to 66.8% with a specificity of 93.6% when the cut-off value was set at 24 IU/mL. Spearman's correlation coefficient between the quantitative results of YHLO CLIA and the titers of CLIFT was 0.59 (p < .01). A significant correlation was found between the anti-dsDNA results detected by YHLO CLIA and the SLE Disease Activity Index 2000 (SLEDAI-2K). Spearman's correlation coefficient between YHLO CLIA and SLEDAI-2K (r = 0.66, p < .01) was higher than that of CLIFT (r = 0.60, p < .01).

CONCLUSIONS

Good correlation and agreement were found between YHLO CLIA and CLIFT. In addition, there was a significant correlation between YHLO CLIA and the SLE Disease Activity Index, which was superior to that of CLIFT. The YHLO chemiluminescence system is recommended for the assessment of disease activity.

Anti-dsDNA antibodies in the classification criteria of systemic lupus erythematosus

Anti-double stranded DNA (dsDNA) antibodies play an important role in the diagnosis, classification and management of systemic lupus erythematosus (SLE), an autoimmune disease characterized by heterogeneous clinical manifestations and a wide range of autoantibodies, which makes the diagnosis quite challenging. In the absence of diagnostic criteria, classification criteria have been used for many decades. The first classification criteria for SLE were formulated in 1971 by the American College of Rheumatology (ACR), followed by two revisions in 1982 and 1997. In order to improve their clinical performance and to reflect new knowledge on autoantibodies, new classification criteria for SLE were issued in 2012 by the Systemic Lupus International Collaborating Clinics (SLICC). These criteria proposed to classify only patients that have at least one immunologic criterion, overcoming SLE classification based solely on clinical manifestations. In 2019, the European League Against Rheumatism (EULAR)/ACR proposed new criteria that aimed to maintain the high specificity of the ACR criteria with a sensitivity close to the SLICC 2012 criteria. These 2019 criteria reinforced the importance of autoantibodies in SLE diagnosis, assigning the highest score (6 points) to anti-dsDNA antibodies in the fully weighted scoring of the disease. The current criteria require the use of an anti-dsDNA assay with at least 90% specificity, such as the Crithidia luciliae immunofluorescence test (CLIFT) or FARR assay. However, the criteria do not comment on all the tests currently widely used in clinical laboratories. Neither do they consider the technological evolutions, nor standardization issues. Since strict adherence to any of the classification criteria, including the serological items, could lead to possible misclassification of SLE and/or delayed diagnosis, test characteristics of the distinct immunoassays should be taken into consideration.

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.

Lack of Association between Serum Interleukin-23 and Interleukin-27 Levels and Disease Activity in Patients with Active Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease characterized by the production of multiple autoantibodies, resulting in tissue and organ damage. Recent studies have revealed that interleukin-23 (IL-23) and interleukin-27 (IL-27) may be therapeutically relevant in selected SLE manifestations. This study aimed to identify associations between serum IL-27 and IL-23 levels and disease activity in Polish patients with different manifestations of SLE: neuropsychiatric lupus (NPSLE), and lupus nephritis (LN). Associations between interleukin levels and oligo-specific antibodies against double-stranded DNA (dsDNA), dose of glucocorticoids, and type of treatment were also analyzed. An enzyme-linked immunosorbent assay was used to assess anti-dsDNA antibodies and analyze the serum concentration of IL-27 and IL-23 from 72 patients aged 19-74 years with confirmed active SLE. Disease activity was measured using the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI 2-K). No significant correlations between interleukin levels and SLEDAI score, anti-dsDNA, corticosteroid dose, or type of treatment were noted. Patients with NPSLE and LN presented the highest median scores of SLEDAI.

The mosaic of autoimmunity - A taste for more. The 12th international congress of autoimmunity 2021 (AUTO12) virtual

Notwithstanding the fact that the 12th international congress of autoimmunity (AUTO12) was held virtual this year, the number of the abstracts submitted and those presented crossed the thousand marks. Leading investigators and researchers from all over the world presented the latest developments of their research in the domain of autoimmunity and its correlation with various diseases. In terms of mechanisms of autoimmunity, an update on the mechanisms behind the association of autoimmunity with systemic diseases focusing on hyperstimulation was presented during AUTO12. In addition, a new mechanism of ASIA syndrome caused by an intrauterine contraceptive device was revealed demonstrating a complete resolution of symptoms following device removal. In regard to the correlation between autoimmunity and neurogenerative diseases, the loss of structural protein integrity as the trigger of immunological response was shown. Schizophrenia as well, and its correlation to pro-inflammatory cytokines was also addressed. Furthermore, and as it was said AUTO12 virtual due to COVID-19 pandemic, various works were dedicated to SARS-CoV-2 infection and COVID-19 in terms of autoimmune mechanisms involved in the pathogenesis, treatment and complications of COVID-19. For instance, the correlation between autoimmunity and the severity of COVID-19 was viewed. Moreover, the presence and association of autoantibodies in COVID-19 was also demonstrated, as well as the clinical outcomes of COVID-19 in patients with rheumatic diseases. Finally, immune-mediated reactions and processes secondary to SARS-CoV-2 vaccination was displayed. Due to the immense importance of all of the topics addressed and while several hundreds of works were presented which cannot be summed up in one paper, we aimed hereby to highlight some of the outstanding abstracts and presentations during AUTO12.

Update and clinical management of anti-DNA auto-antibodies

Anti-deoxyribonucleic acid (DNA) antibodies in the clinical laboratory are intimately linked to the diagnosis and monitoring of systemic lupus erythematosus (SLE); however, the characteristics of the analytical methods and the properties of the antibodies themselves are heterogeneous. To review the definition and properties of anti-double-stranded anti-DNA (anti-dsDNA) antibodies, the adequacy of analytical methods, and the clinical requirements for this biomarker. Through PubMed we searched the existing literature with the terms anti-dsDNA, editorial, review, guideline, meta-analysis and SLE. The last search, anti-dsDNA and SLE restricted to the last two years. Information was expanded through related articles and those published in official state bodies related to anti-dsDNA and SLE. Clinical laboratory methods for anti-dsDNA analysis and their characteristics are analyze. The clinical utility of anti-dsDNA in its diagnostic, clinical association and follow-up aspects of SLE is reviewed. There is wide variability in analytical methods and deficits in standardization persist. They are part of the current SLE classification criteria and are used as markers in the follow-up of the disease. Their diagnostic usefulness improves when they are determined in antinuclear antibody (ANA)-positive patients. In follow-up, quantification is of interest, preferably with the same analytical method (given the deficits in standardization).

The perspective on standardisation and harmonisation: the viewpoint of the EASI president

Standardisation of immuno-assays for autoantibodies is a major challenge. Although multiple organisations participate in the generation of internationally accepted standards, adequate standardisation of assays has not yet been achieved. Harmonisation may offer an alternative approach to better align requesting, testing, reporting and interpretation of autoimmune diagnostics. The European Autoimmunity Standardisation Initiative (EASI) was founded to facilitate both standardisation as well as harmonisation of autoantibody tests, but over the years the focus has drifted away from standardisation in favour of harmonisation. In the current paper the options for harmonisation are highlighted.