Anti-neutrophil cytoplasm antibodies (ANCA): Recent methodological advances-Lead to new consensus recommendations for ANCA detection

Performance of two multiplex flow cytometric assays for antibody detection in Egyptian patients

Background

Autoantibodies are vital biomarkers for the diagnosis, assessment and prognostic determination of various autoimmune disorders.

Objective

This study aimed to evaluate the performance of the two AtheNA Multi-Lyte^® systems for the detection of various autoantibodies.

Methods

A total of 105 systemic lupus erythematosus patients, 35 patients with other autoimmune diseases (diseased controls), and 30 healthy volunteers (healthy controls) at Zagazig University Hospitals, Zagazig city, Al Sharqia governorate were tested for anti-double-stranded DNA (anti-dsDNA) antibodies using indirect immunofluorescence (IIF) and the AtheNA Multi-Lyte^® anti-nuclear antibodies-II system between May 2020 and April 2022. Seventy-five patients with clinically suspected autoimmune vasculitis (AIV) and 25 healthy volunteers were also tested for anti-myeloperoxidase and anti-proteinase 3 antibodies using IIF, the AtheNA Multi-Lyte^® AIV system, and enzyme-linked immunosorbent assay (ELISA).

Results

The AtheNA anti-dsDNA test (98.5%) was more specific than IIF (96.9%) for diagnosing systemic lupus erythematosus, but both tests had the same sensitivity (38.1%). Combining both methods increased sensitivity to 47.6%, while increasing the cut-off of the AtheNA anti-dsDNA test to 134 international units/mL increased specificity to 100%. The AtheNA Multi-Lyte AIV system exhibited substantial agreement with IIF regarding anti-myeloperoxidase testing (κ = 0.65) and almost perfect agreement with ELISA (κ = 0.85). The AtheNA Multi-Lyte^® AIV system exhibited perfect agreement with IIF (κ = 1) and substantial agreement with ELISA for anti-proteinase 3 testing (κ = 0.63).

Conclusion

AtheNA Multi-Lyte^® systems appear to be reliable for anti-dsDNA, anti-myeloperoxidase, and anti-proteinase 3 screening and may be an optimal choice for monitoring anti-dsDNA levels.

What this study adds

It is necessary to evaluate various autoantibodies detection assays to increase both sensitivity and specificity of autoimmune diseases diagnostic approaches. AtheNA Multi-Lyte^® systems appear to be reliable for anti-dsDNA, anti-myeloperoxidase, and anti-proteinase 3 screening and may be an optimal choice for monitoring anti-dsDNA levels.

Clinical, Methodological, and Practical Considerations for Algorithmic Testing in Autoimmune Serology

BACKGROUND

Autoimmune serology tests are central to the classification, screening, diagnosis, and monitoring of a variety of autoimmune disorders. To improve the appropriateness of serologic evaluation and support laboratory resource utilization, reflex testing approaches have been proposed and implemented across clinical laboratories. Reflex testing involves a staged approach where an initial test result triggers subsequent tests based on prespecified rules.

CONTENT

Various reflex testing approaches in the context of antinuclear antibody-associated rheumatic disease, antineutrophil cytoplasmic autoantibody-associated vasculitis, celiac disease, and myasthenia gravis are reviewed here. Clinical, analytical, and practical considerations of reflex testing implementation are addressed as well as associated limitations and challenges.

SUMMARY

Serology reflex testing algorithms for the evaluation of autoimmune diseases can support clinical diagnosis and laboratory resource use but may be challenging to implement and are often applied variably across institutions. Assessments of evidence-driven guidelines, clinical impact, and impact on laboratory workflow are essential to this task.

Antineutrophil cytoplasmic antibodies (ANCA) - their role in pathogenesis, diagnosis, and treatment monitoring of ANCA-associated vasculitis

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) constitutes a group of rare diseases characterized by necrotizing inflammation of small blood vessels and the presence of ANCA. Increasing clinical and experimental evidences support their pathogenic role in AAV, but the exact mechanism is not fully understood. Recently, the important role of neutrophil extracellular traps (NETs) in pathogenesis of AAV is underlined. There is an indication that NETs can be a source for the formation of ANCA. The most common ANCA target antigens are myeloperoxidase (MPO) and proteinase 3 (PR3). Though the mechanism of action of ANCA is still under exploration, ANCA serology is being increasingly used for classification of AAV and revealed as kenner in defining various disease subsets associated with different genetic background, clinical features, treatment response, and prognosis. Controversy exists regarding the utility of serial measurements of ANCA in patients with AAV to monitor treatment and predict disease relapse.

[Chances and Pitfalls of ANA and ANCA Diagnostics]

Chances and Pitfalls of ANA and ANCA Diagnostics Abstract. In the context of clinical manifestations, if analysed with high quality laboratory methods and correctly interpreted, ANA and ANCA are an essential tool in the differential diagnosis of rheumatic diseases. Neither ANA nor ANCA, however, are pathognomonic markers of rheumatic diseases and they do not have a reliable negative predictive value. Commercially available screening tests such as ENA screen or CTD screen are offered widely. Unfortunately, the results from such tests may in some cases create more insecurity rather than confirming the diagnosis, as the presented case shows.

[ANCA-associated vasculitides : State of the art]

Granulomatosis with polyangiitis (GPA, formerly Wegener's granulomatosis) and microscopic polyangiitis (MPA) are associated with the detection of antibodies against neutrophilic cytoplasmic antigens (ANCA) and are referred to as ANCA-associated vasculitides (AAV). In the event of the clinical suspicion of AAV the ANCA should first be determined by means of an antigen-specific immunoassay for proteinase 3‑ANCA and myeloperoxidase-ANCA, according to current consensus recommendations. The diagnosis of AAV should also be confirmed by biopsy if possible. The classification criteria for AAV are currently being revised. Diagnostic criteria do not exist. The standard induction therapy consists of rituximab or cyclophosphamide, each in combination with glucocorticoids (GC). In the absence of severe organ involvement, methotrexate can alternatively be used. Recent study data suggest that additive plasmapheresis does not improve the long-term outcome. After remission, remission-preserving treatment with azathioprine, methotrexate or rituximab should be given for at least 48 months. The risk of severe infections is markedly increased, especially during the remission induction phase but can also be reduced during treatment with rituximab by the prophylactic administration of trimethoprim-sulfamethoxazole. In view of the increased risk of infection, GC-reduced or GC-free treatment regimens are currently the focus of clinical development.