Current and emerging techniques for ANCA detection in vasculitis

EVOLVE: The Australian Rheumatology Association's 'top five' list of investigations and interventions doctors and patients should question

BACKGROUND

The EVOLVE (evaluating evidence, enhancing efficiencies) initiative aims to drive safer, higher-quality patient care through identifying and reducing low-value practices.

AIMS

To determine the Australian Rheumatology Association's (ARA) 'top five' list of low-value practices.

METHODS

A working group comprising 19 rheumatologists and three trainees compiled a preliminary list. Items were retained if there was strong evidence of low value and there was high or increasing clinical use and/or increasing cost. All ARA members (356 rheumatologists and 72 trainees) were invited to indicate their 'top five' list from a list of 12-items through SurveyMonkey in December 2015 (reminder February 2016).

RESULTS

A total of 179 rheumatologists (50.3%) and 19 trainees (26.4%) responded. The top five list (percentage of rheumatologists, including item in their top five list) was: Do not perform arthroscopy with lavage and/or debridement for symptomatic osteoarthritis of the knee nor partial meniscectomy for a degenerate meniscal tear (73.2%); Do not order anti-nuclear antibody (ANA) testing without symptoms and/or signs suggestive of a systemic rheumatic disease (56.4%); Do not undertake imaging for low back pain for patients without indications of an underlying serious condition (50.8%); Do not use ultrasound guidance to perform injections into the subacromial space as it provides no additional benefit in comparison to landmark-guided injection (50.3%) and Do not order anti-double-stranded DNA antibodies in ANA negative patients unless the clinical suspicion of systemic lupus erythematosus remains high (45.3%).

CONCLUSIONS

This list is intended to increase awareness among rheumatologists, other clinicians and patients about commonly used low-value practices that should be questioned.

Platelet to lymphocyte ratio is associated with the current activity of ANCA-associated vasculitis at diagnosis: a retrospective monocentric study

Platelet to lymphocyte ratio (PLR) has been introduced as a useful index to estimate the current inflammatory burdens in various diseases. In this study, we investigate whether PLR is associated with the severity of ANCA-associated vasculitis (AAV). We retrospectively reviewed the medical records of 163 patients with AAV, collected clinical, laboratory and radiological data and calculated Birmingham vasculitis activity score (BVAS). We defined the lower limit of the highest tertile of BVAS as the cut-off for severe AAV (BVAS ≥ 16). The optimal cut-off of PLR for severe AAV was set as 272.0. The odds ratio (OR) of PLR for severe AAV was assessed using the univariable and multivariable logistic regression analyses. The median age at diagnosis was 58.0 years and 51 patients (31.3%) were men. Patients with severe AAV exhibited higher rate of ANCA positivity and higher blood urea nitrogen (BUN), creatinine (Cr), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) than those without. Patients with severe AAV exhibited significantly increased median PLR compared to those without (299.3 vs. 184.0). In the univariable binary logistic regression analysis, BUN ≥ 17.45 mg/dL (OR 3.730), Cr ≥ 1.12 mg/dL (OR 3.519), ESR ≥ 83.5 mm/h (OR 2.785), CRP ≥ 20.0 mg/L (OR 2.612), PLR ≥ 272.0 (OR 4.231) and ANCA positivity (OR 2.306) were associated with severe AAV. In the multivariable binary logistic regression analysis, only PLR ≥ 272.0 was an independent predictor of severe AAV at diagnosis (OR 2.734, 95% CI 1.247, 5.993). In conclusion, PLR at diagnosis is associated with the current activity of vasculitis in AAV patients.

Neutrophil to lymphocyte ratio at diagnosis can estimate vasculitis activity and poor prognosis in patients with ANCA-associated vasculitis: a retrospective study

BACKGROUND

Neutrophil to lymphocyte ratio (NLR) was introduced to predict poor prognosis in various diseases, but not all variants of ANCA-associated vasculitis (AAV). In this study, we aimed to investigate whether NLR at diagnosis can estimate vasculitis activity at diagnosis and poor prognosis during follow-up in patients with AAV.

METHODS

We retrospectively reviewed the medical records of 160 patients with AAV. We collected clinical and laboratory data at diagnosis and obtained remission and death as poor prognosis. We stratified AAV patients into three groups according to tertile and defined the lower limit of each highest tertile as the optimal cut-off (5.9 for NLR and 15.0 of Birmingham vasculitis activity score [BVAS] for severe AAV).

RESULTS

The mean age at diagnosis was 55.2 years and 48 patients were men. In the univariable linear regression analysis, BVAS was negatively correlated with lymphocyte count and positively correlated with erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and NLR. In the multivariable linear regression analyses of ESR and CRP with either lymphocyte count or NLR, lymphocyte count (β = - 0.160) and NLR (β = 0.169) were associated with BVAS. Patients having NLR ≥ 5.9 exhibited severe AAV more frequently than those having NLR < 5.9 at diagnosis (relative 2.189, P = 0.023). Patients having NLR ≥ 5.9 exhibited a higher frequency of AAV relapse, but not death, than those having NLR < 5.9 (P = 0.016).

CONCLUSIONS

NLR at diagnosis can estimate vasculitis activity at diagnosis and predict relapse during follow-up in patients with AAV.

Cutaneous Manifestations of ANCA-Associated Small Vessels Vasculitis

Skin lesions are frequent manifestations of underlying systemic conditions, including systemic autoimmune vasculitis. In particular, anti-neutrophil cytoplasmic antibodies (ANCA) are associated with distinct forms of vasculitis characterized by inflammatory cell infiltration of the walls of small and medium-sized vessels leading to vascular destruction and tissue necrosis. ANCA-associated vasculitis is rare and systemic diseases, which can be classified based on different distribution of vascular inflammation and presence or absence of granulomatosis and asthma. Despite their diversities, ANCA-associated vasculitis, namely microscopic polyangiitis, granulomatosis with polyangiitis and eosinophilic granulomatosis with polyangiitis, can all display a broad variety of cutaneous manifestations, which can appear during the course of the disease or even as first sign at the time of onset. Different skin manifestations might coexist in the same patient and occur in different occasions during the course of the vasculitis. Thus, a deep knowledge of the spectrum of skin lesions as part of ANCA-associated vasculitis is mandatory for a correct diagnostic process, whenever cutaneous vasculitis is suspected. Due to this broad variety of manifestations, the diagnosis of skin involvement in ANCA-associated vasculitis is very challenging and it must be supported by a detailed medical history, accurate physical examination, specific histopathological analysis of skin biopsy and the presence of ANCA serology. In this review, we focus on the cutaneous manifestations that can develop in the context of ANCA-associated vasculitis, detailing the clinical features, the histopathological aspects as well as the direct immunofluorescence studies for each of the three conditions. Moreover, we acknowledged the differential diagnoses that must be ruled out in the diagnostic process and the main therapeutic approaches available for treatment of ANCA-associated vasculitis.

Delta Neutrophil Index Is Associated with Vasculitis Activity and Risk of Relapse in ANCA-Associated Vasculitis

PURPOSE

Delta neutrophil index (DNI) represents the immature granulocytes count associated with neutrophil-consumption. We investigated whether DNI might be associated with Birmingham vasculitis activity score (BVAS) at diagnosis and could predict relapse during the follow-up in patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV).

MATERIALS AND METHODS

We reviewed the medical records of 97 patients having DNI results. Twenty patients had granulomatosis with polyangiitis (GPA), 58 had microscopic polyangiitis (MPA), and 19 had eosinophilic GPA (EGPA). We collected clinical and laboratory data including BVAS, five factor score (FFS), and DNI. The correlation coefficient and cumulative relapse free survival rate were obtained. The optimal cut-off of DNI was extrapolated by calculating the area under the receiver operator characteristic curve.

RESULTS

DNI was significantly related to cross-sectional BVAS. Furthermore, among continuous variables, only DNI could reflect BVAS of GPA and MPA, but not EGPA. Severe AAV was defined as BVAS ≥20 (the highest quartile). At diagnosis, patients having DNI ≥0.65% had a significantly higher risk of severe GPA and MPA than those having not (relative risk 4.255) at diagnosis. During the follow-up, DNI ≥0.65% could predict the higher relapse rate.

CONCLUSION

DNI could reflect BVAS at diagnosis and furthermore, DNI ≥0.65% could not only identify severe AAV at diagnosis, but also predict relapse during the follow-up in patients with GPA and MPA.

New concepts in ANCA detection and disease classification in small vessel vasculitis: the role of ANCA antigen specificity

Anti-neutrophil cytoplasmic antibodies (ANCA) play a central role in the diagnosis and pathogenesis of patients with ANCA-associated vasculitis. ANCA-associated vasculitis is a rare disease characterized by necrotizing inflammation of small/medium-sized blood vessels with and without granuloma in different organs. The main syndromes are granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic GPA. ANCA in these diseases are almost always directed against proteinase 3 and myeloperoxidase. Most laboratories worldwide use as standard the indirect immunofluorescence technique to screen for ANCA and then confirm positive IFT results with antigen specific immunoassyas for PR3- and MPO-ANCA. New guidelines for ANCA testing have been developed based on a recent European multicentre study, and according to the revised 2017 international consensus recommendations, testing for ANCA in small vessel vasculitis can be done by PR3- and MPO-ANCA immunoassays, without the categorical need for IIF. The new testing strategy for ANCA in vasculitis directly identifies the ANCA target antigen and has a particular value for the AAV sub-classification. Recent studies have shown that AAV can be classified based on ANCA serotype. ANCA presence and the antigen specificity also may have important value as a prognostic factor and may serve as a guide for immunosuppressive therapy. The clinical utility of ANCA depends on the type of assay performed and the appropiate ordering of testing the right clinical setting. Accurate identification of all patients with AAV and the avoidance of misdiagnosis can be achieved using a "gating policy" based on clinical information given to the laboratory at the time of request.

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

The current practice for detection of anti-neutrophil cytoplasm antibodies (ANCA) directed against proteinase 3 (PR3) and myeloperoxidase (MPO) has been screening by indirect immunofluorescence (IIF) followed by an antigen specific tests for PR3- and MPO-ANCA. However, ANCA diagnostics have undergone many technical developments that have affected the 1999 international consensus recommendations, and lead to a revision of the existing ANCA detection strategy. Recent European multicentre studies have compared the diagnostic performance of various ANCA detection methods and demonstrated that PR3- and MPO-ANCA immunoassays yielded the highest diagnostic accuracy. New guidelines for ANCA testing have been developed based on these data. According to the revised 2017 international consensus recommendations, testing for ANCA in small vessel vasculitis can be done by PR3- and MPO-ANCA immunoassays, without the categorical need for IIF. Thus, IIF can be discarded completely, or can be used as confirmation assays instead a screening test. Clearly, though, the new testing strategy for ANCA in vasculitis must identify the ANCA target antigen, as PR3- and MPO-ANCA serotype correlate well with disease expression. Furthermore, recent studies have shown that AAV can be classified based on ANCA serotype, since PR3- and MPO-ANCA- diseases are strongly associated with distinguishable genetic alleles, different clinical and histological features. ANCA presence and the antigen specificity also may have important value as a prognostic factor and may serve as a guide for immunosuppressive therapy. In the current review, we summarize the novelties in ANCA testing, present the 2017 revised international consensus on ANCA testing in vasculitis, evaluate the diagnostic significance of ANCA, and discuss the role of ANCA serotypes in the diagnostic work-up of patients with AAV.

Value of non-identified ANCA (non-PR3, non-MPO) in the diagnosis of granulomatosis with polyangiitis (Wegener's granulomatosis)

OBJECTIVE

Determine the frequency of granulomatosis with polyangiitis (GPA) associated with non-identified ANCA (non-MPO, non-PR3 ANCA) and secondarily compare their clinic with GPA associated with MPO-positive or PR3-positive ANCA.

METHODS

In a monocentric retrospective observational study, clinical data of 398 patients with non-identified ANCA (titer of ANCA at least 1/80 by immunofluorescence on ethanol fixed PMN) was gathered over a period of 6 years. GPA patients from this population were compared with GPA patients with identified ANCA on the basis of clinical, biological, immunological and histological features.

RESULTS

The most common diseases associated with non-identified ANCA were inflammatory bowel diseases accounting for 17% of diseases. GPA accounted for only 1.8% of cases. There were no significant differences in terms of clinical and histological characteristics between GPA with non-identified ANCA and GPA with identified ANCA, but significantly higher CRP levels were observed in GPA patients with identified ANCA (p = 0.005). Localized disease (ear, nose and throat and/or lung involvement without any other systemic involvement) was more frequent in the group of GPA with nonidentified ANCA (p = 0.047) as compared to GPA with identified ANCA. This explains that the former group of patients was less frequently treated by cyclophosphamide than the latter (p = 0.016).

CONCLUSION

GPA with non-MPO, non-PR3 ANCAs is relatively rare. Our study suggests that GPA with nonidentified ANCA differs from GPA with identified ANCA by the frequency of localized forms.

A multicentre study to improve clinical interpretation of proteinase-3 and myeloperoxidase anti-neutrophil cytoplasmic antibodies

Objective

The objective of this multicentre study was to improve the clinical interpretation of PR3- and MPO-ANCAs as an adjunct for the diagnosis of ANCA-associated vasculitis (AAV) by defining thresholds and test result intervals based on predefined specificities and by calculating test result interval-specific likelihood ratios (LRs).

Methods

Eight different PR3- and MPO-ANCA immunoassays from seven companies were evaluated using 251 diagnostic samples from AAV patients and 924 diseased controls.

Results

Thresholds for antibody levels were determined based on predefined specificities (95, 97.5, 99 and 100%) and used to delimit test result intervals. Test result interval-specific LRs were determined. For all assays, the LR for AAV increased with increasing antibody level. For all but one immunoassay, high antibodies levels (associated with LR >55) were found in a substantial fraction (>65%) of patients. The area under the curve (AUC) of receiver operating characteristics analysis of a diagnostic approach in which positive results were confirmed by IIF or another immunoassay was not substantially higher than the AUC of performing immunoassay only. The highest AUC was found when immunoassay was combined with another immunoassay or with IIF.

Conclusion

To diagnose AAV based on PR3- and MPO-ANCA, it is useful to define thresholds for antibody levels and to assign test result interval-specific LRs. Higher antibody levels are associated with a higher likelihood for disease. Such information improves clinical interpretation.

Position paper: Revised 2017 international consensus on testing of ANCAs in granulomatosis with polyangiitis and microscopic polyangiitis

Anti-neutrophil cytoplasmic antibodies (ANCAs) are valuable laboratory markers used for the diagnosis of well-defined types of small-vessel vasculitis, including granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). According to the 1999 international consensus on ANCA testing, indirect immunofluorescence (IIF) should be used to screen for ANCAs, and samples containing ANCAs should then be tested by immunoassays for proteinase 3 (PR3)-ANCAs and myeloperoxidase (MPO)-ANCAs. The distinction between PR3-ANCAs and MPO-ANCAs has important clinical and pathogenic implications. As dependable immunoassays for PR3-ANCAs and MPO-ANCAs have become broadly available, there is increasing international agreement that high-quality immunoassays are the preferred screening method for the diagnosis of ANCA-associated vasculitis. The present Consensus Statement proposes that high-quality immunoassays can be used as the primary screening method for patients suspected of having the ANCA-associated vaculitides GPA and MPA without the categorical need for IIF, and presents and discusses evidence to support this recommendation.

Involvement of the Peripheral Nervous System in Polyarteritis Nodosa and Antineutrophil Cytoplasmic Antibodies-Associated Vasculitis

Peripheral nerve involvement is common in polyarteritis nodosa and the antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitides. The underlying mechanism is arteritis of the vasa nervorum, leading to ischemic neuropathy. The classic presentation is stepwise involvement of peripheral nerves with ongoing antecedent constitutional symptoms. This article reviews the pathologic findings, clinical syndromes, diagnosis, and treatment of ANCA-associated vasculitides.

Vasculitis for the internist: focus on ANCA-associated vasculitis

Vasculitides comprise several diseases affecting vessels of different sizes, mainly arteries, but also capillaries and veins. Antineutrophil cytoplasm antibody-associated vasculitides (AAVs) belong to the systemic necrotizing small-vessel vasculitis group that comprises granulomatosis with polyangiitis, microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis. Internists often see AAV patients, and although their outcomes are usually good, the disease can be responsible for morbidity and mortality. Herein, after reviewing the literature, we concentrate on selected aspects important for the internist, including classification, diagnostic dilemmas, treatment novelties, and follow-up.

Discrepancies between two immunoassays for the determination of MPO and PR3 autoantibodies

BACKGROUND

Testing for autoantibodies to myeloperoxidase (MPO) and proteinase 3 (PR3) is part of anti-neutrophil cytoplasmic antibodies (ANCA) test that aids the diagnosis of a number of autoimmune diseases including small-vessel vasculitis. We characterized the differences between two automated immunoassays at three facilities for measuring MPO- and PR3-ANCA autoantibodies.

METHODS

117 serum samples were analyzed for MPO and PR3 autoantibodies. The INOVA QUANTA Lite® IgG assay (INOVA Diagnostics) were performed at two facilities and the Bio-Plex® 2200 Vasculitis Panel (Bio-Rad) were performed at a third reference lab. The results were compared both qualitatively (between INOVA QUANTA Lite® and Bio-Plex® methods) and quantitatively (between two sites performing INOVA QUANTA Lite® assays).

RESULTS

Comparison of the INOVA QUNATA Lite® assays at two different facilities (n=36) demonstrated high concordance (97.2% for MPO and 94.4% for PR3) and quantitative correlation (R²=0.973 for MPO and R²=0.935 for PR3). Conversely, INOVA QUNATA Lite® and Bio-Plex® methods showed poor concordance at 70.4% for MPO (n=81; 95% CI: 59.7% to 79.2%) and at 76.5% for PR3 (n=81; 95% CI: 66.2% to 84.4%).

CONCLUSION

This study demonstrated low concordance between two methods for MPO-ANCA and PR3-ANCA measurements. Given the discrepancies, the performance of different autoantibody immunoassay methods should be taken into consideration when evaluating MPO-ANCA and PR3-ANCA results.

Pathophysiology of ANCA-associated Vasculitis

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is characterized as inflammation of small-sized to medium-sized blood vessels and encompasses several clinicopathologic entities including granulomatosis with polyangiitis, microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis, and renal-limited ANCA-associated vasculitis. Over the past several decades, significant progress has been made in understanding the pathophysiology of ANCA-associated vasculitis. Although neutrophils contain a multitude of granular proteins, clinically significant autoantibodies are only recognized against myeloperoxidase and proteinase 3, both of which are present in the azurophilic granules. The propensity to develop these antibodies depends on a variety of predisposing factors such as microbial infection, genetic factors, environmental agents, and therapeutic drugs among others. These factors are usually associated with production of proinflammatory cytokines with capacity to prime the neutrophils. As a result a high proportion of neutrophils in circulation may be primed resulting in exposure of cytoplasmic proteins including myeloperoxidase and proteinase 3 on the surface of the neutrophils. Primed neutrophils are activated by interaction with ANCA in circulation. Activated neutrophils attach to and transmigrate through endothelium and accumulate within the vessel wall. These neutrophils degranulate and produce reactive oxygen radicals and ultimately die, causing tissue injury. Endothelial injury results in leakage of serum proteins and coagulation factors causing fibrinoid necrosis. B cells produce ANCAs, as well as neutrophil abnormalities and imbalances in different T-cell subtypes with excess of Th17, which perpetuate the inflammatory process.

A novel strategy with combined assays for detection of anti-neutrophil cytoplasmic antibody (ANCA) in clinically ANCA-negative granulomatosis with polyangiitis patients

OBJECTIVE

Granulomatosis with polyangiitis (GPA) that is localized to the upper airway presents a diagnostic challenge because of a tendency towards anti-neutrophil cytoplasmic antibody (ANCA)-negativity. The purpose of this study was to investigate whether positivity of ANCA detection might be elicited with combined use of enzyme-linked immunosorbent assay (ELISA) kits.

METHODS

Twenty-nine serum samples obtained from GPA patients were used in this study. In addition to routine biochemical investigation for ANCA, tests for detecting PR3-, MPO-ANCAs, and minor ANCAs were performed with commercially available ELISA kits. Cytoplasmic (C)-ANCA and perinuclear (P)-ANCA were evaluated using the indirect immunofluorescence (IIF) technique.

RESULTS

Twelve patients were positive for PR3- or MPO-ANCA in the clinical laboratory test, and 17 patients were negative for both ANCAs. Of the 17 ANCA-negative patients, four were positive for PR3- or MPO-ANCA, and three were positive for minor ANCA according to results obtained from six different ELISA kits. These findings indicated that performing detection tests with six different ELISA kits might improve the positivity of ANCA and might contribute to establishing the diagnosis of ANCA-associated vasculitis. Together with results from IIF, the samples of eight patients with clinically ANCA-negative results (8/17, 47.1%) were converted to ANCA-positive results, and the ANCA detection rate was significantly improved from 12/29 (41.4%) to 20/29 (69.0%, p=0.03).

CONCLUSIONS

Additional detection techniques should be used to confirm the results of clinically ANCA-negative samples, particularly when vasculitis is suspected. Minor ANCAs should also be evaluated with detection tests when PR3- and MPO-ANCA are negative.

Neutrophil Extracellular Traps Contain Selected Antigens of Anti-Neutrophil Cytoplasmic Antibodies

Neutrophil extracellular traps (NETs) are chromatin filaments decorated with enzymes from neutrophil cytoplasmic granules. Anti-neutrophil cytoplasmic antibodies (ANCAs) bind to enzymes from neutrophil cytoplasmic granules and are biomarkers for the diagnosis of systemic vasculitides. ANCA diagnostics are based on indirect immunofluorescence (IIF) of ethanol-fixed neutrophils. IIF shows a cytoplasmic staining pattern (C-ANCA) due to autoantibodies against proteinase 3 (PR3) or a perinuclear staining pattern (P-ANCA) due to autoantibodies against myeloperoxidase (MPO). The distinct ANCA-staining patterns are an artifact of ethanol fixation. Here, we tested NETs as a substrate for the detection of ANCAs in human sera. We observed that P-ANCAs specifically stained NETs, while C-ANCAs targeted the cell bodies of netting neutrophils. The distinct ANCA-staining patterns were caused by the presence of MPO, but not PR3, in NETs. Using NETs as a substrate for IIF, we characterized ANCAs in sera of patients with ANCA-associated vasculitis (AAV). Furthermore, we inhibited serine proteases by diisopropylfluorophosphate to prevent chromatin unfolding and the release of NETs and thus generated neutrophils with MPO-positive nuclei and PR3-positive cytoplasm, which resembled the appearance of ethanol-fixed neutrophils. In conclusion, our data suggest that NETs are selectively loaded with antigens recognized by P-ANCAs, and netting neutrophils provide a physiological substrate for ANCA detection in patients with AAV.

[Paradigm shift in ANCA diagnostics : New international consensus recommendations]

BACKGROUND

Up to now indirect immunofluorescence (IIF) followed by an antigen-specific assay specific for proteinase 3 (PR3) or myeloperoxidase (MPO) has been the standard method for the detection of antineutrophil cytoplasmic antibodies (ANCA). The development of more sensitive and highly specific PR3-ANCA and MPO-ANCA immunoassays for the diagnosis of ANCA-associated vasculitis (AAV) has raised doubts about the two-stage diagnostic strategy currently recommended for ANCA detection.

OBJECTIVE

Presentation and discussion of the new international consensus recommendations on ANCA testing in AAV.

METHODS

This article presents the new guidelines for ANCA testing that have been developed based on the results of a recent large multicenter study by the European Vasculitis Society (EUVAS). The draft of the author committee was revised by each contributor and subsequently distributed to 12 experts on 4 continents. After further revision the final document was returned for ratification and submitted for publication.

RESULTS/CONCLUSION

The current study results confirm the superiority of the diagnostic value of antigen-specific immunoassays compared to IIF. The current consensus recommendations support the primary use of PR3-ANCA and MPO-ANCA immunoassays for diagnostic evaluation of patients with AAV without the categorical need for additional IIF.

Detection of antineutrophil cytoplasmic antibodies (ANCAs): a multicentre European Vasculitis Study Group (EUVAS) evaluation of the value of indirect immunofluorescence (IIF) versus antigen-specific immunoassays

OBJECTIVE

This multicentre study was performed to evaluate the diagnostic accuracy of a wide spectrum of novel technologies nowadays available for detection of myeloperoxidase (MPO) and proteinase 3 (PR3)-antineutrophil cytoplasmic antibodies (ANCAs).

METHODS

Sera (obtained at the time of diagnosis) from 251 patients with ANCA-associated vasculitis (AAV), including granulomatosis with polyangiitis and microscopic polyangiitis, and from 924 disease controls were tested for the presence of cytoplasmic pattern/perinuclear pattern and atypical ANCA (A-ANCA) by indirect immunofluorescence (IIF) (at two sites) and for the presence of PR3-ANCA and MPO-ANCA by eight different immunoassays.

RESULTS

The area under the curve (AUC) of the receiver operating characteristic curve to discriminate AAV from controls was 0.923 (95% CI 0.902 to 0.944) and 0.843 (95% CI 0.814 to 0.871) for the two IIF methods. For the antigen-specific immunoassays, the AUC varied between 0.936 (95% CI 0.912 to 0.960) and 0.959 (95% CI 0.941 to 0.976), except for one immunoassay for which the AUC was 0.919 (95% CI 0.892 to 0.945).

CONCLUSIONS

Our comparison of various ANCA detection methods showed (i) large variability between the two IIF methods tested and (ii) a high diagnostic performance of PR3-ANCA and MPO-ANCA by immunoassay to discriminate AAV from disease controls. Consequently, dual IIF/antigen-specific immunoassay testing of each sample is not necessary for maximal diagnostic accuracy. These results indicate that the current international consensus on ANCA testing for AAV needs revision.

ANCA-associated vasculitis - clinical utility of using ANCA specificity to classify patients

The anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are a heterogeneous group of rare syndromes characterized by necrotizing inflammation of small and medium-sized blood vessels and the presence of ANCAs. Several clinicopathological classification systems exist that aim to define homogeneous groups among patients with AAV, the main syndromes being microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA) and eosinophilic GPA (EGPA). Two main types of ANCA can be detected in patients with AAV. These ANCAs are defined according to their autoantigen target, namely leukocyte proteinase 3 (PR3) and myeloperoxidase (MPO). Patients with GPA are predominantly PR3-ANCA-positive, whereas those with MPA are predominantly MPO-ANCA-positive, although ANCA specificity overlaps only partially with these clinical syndromes. Accumulating evidence suggests that ANCA specificity could be better than clinical diagnosis for defining homogeneous groups of patients, as PR3-ANCA and MPO-ANCA are associated with different genetic backgrounds and epidemiology. ANCA specificity affects the phenotype of clinical disease, as well as the patient's initial response to remission-inducing therapy, relapse risk and long-term prognosis. Thus, the classification of AAV by ANCA specificity rather than by clinical diagnosis could convey clinically useful information at the time of diagnosis.

Variability in Testing for Antineutrophil Cytoplasmic Antibodies: A Survey of Participants in the College of American Pathologists Proficiency Testing Program

CONTEXT

-Variability in testing for antineutrophil cytoplasmic antibodies (ANCAs) contributes to confusion and controversy related to testing for vasculitis and other ANCA-associated diseases.

OBJECTIVES

-To survey laboratory testing practices regarding ANCA testing and to investigate differences in testing algorithms.

DESIGN

-Supplemental questions were sent to the 333 laboratories participating in the College of American Pathologists proficiency testing program for ANCA as part of the Special Immunology S2 Survey.

RESULTS

-A total of 315 laboratories submitted responses to the supplemental questions. Only 88 of 315 participants (28%) reported using a combination of indirect immunofluorescence (IFA) and enzyme immunoassay (EIA) techniques as recommended by current guidelines, with a few additional labs using IFA and multiplex bead assay as an acceptable alternative to EIA. Other labs reported using only IFA, EIA, or multiplex bead assays.

CONCLUSIONS

-A wide variety of testing algorithms are in use for ANCA testing despite evidence to suggest that a combination of IFA and EIA testing provides the most comprehensive information. Laboratories should inform clinicians clearly about testing practices and utility of testing in specific disease states.

Autoantibodies and their Judicious Use in Pediatric Rheumatology Practice

Autoantibody testing forms an important part of diagnostic workup of patients in Pediatric rheumatology practice. However it is important to understand that the mere presence of autoantibodies does not necessarily mean the presence of an underlying autoimmune disease. Autoantibodies may be present decades before the development of clinical manifestations of an autoimmune disease and may be viewed as harbingers of Autoimmune disease. On the other hand, low-affinity autoantibodies may be present in normal healthy individuals; these natural autoantibodies serve an important function in immune regulation and tolerance. Autoantibody testing in pediatric practice mainly includes testing for anti-nuclear antibodies, anti-dsDNA antibodies, anti-neutrophil cytoplasmic autoantibodies and antiphospholipid antibodies. Rheumatoid factor and anti-CCP do not have much significance in the diagnostic schema in pediatric rheumatology, except perhaps for classification of juvenile idiopathic arthritis (JIA) and prognostication in late-onset polyarticular JIA. The positive predictive value (PPV) of any laboratory test depends on the prevalence of the disease in the population being tested. Hence, test ordering practices greatly impact the performance characteristics and positive predictive value of any laboratory test. A restricted test ordering only in patients with clinical signs and symptoms suggestive of autoimmune disease would thus greatly increase the PPV of tests such as antinuclear antibody used for diagnosing autoimmunity.

Can antineutrophil cytoplasmic antibody levels be used to inform treatment of pauci-immune vasculitis?

PURPOSE OF REVIEW

The role of serial antineutrophil cytoplasmic antibody (ANCA) measurements to guide immunosuppressive therapy in pauci-immune vasculitis is an area of ongoing controversy. Evidence elucidating the relationship between ANCA levels and disease activity continues to grow.

RECENT FINDINGS

The finding that proteinase 3-ANCA and myeloperoxidase-ANCA-associated diseases differ genetically has challenged the traditional classification and study of pauci-immune vasculitis. Multiple studies have also found that the clinical features and course of disease differ by ANCA antigen specificity more than clinical diagnosis. Advances in diagnostic assays and new techniques for the evaluation of ANCA levels over time have yielded improved assay performance in specific subsets of patients. In addition, increasing use of rituximab has added to our understanding of the relationship of ANCA levels to B-cell counts and disease relapse, which may differ by treatment regimen.

SUMMARY

The relationship between ANCA levels and disease activity is impacted by multiple factors, including antigen specificity, disease manifestations, clinical assay, and therapeutic regimen. Each of these must be taken into account when determining the significance of ANCA levels during long-term follow-up of pauci-immune vasculitis.

Peripheral blood natural killer cell percentages in granulomatosis with polyangiitis correlate with disease inactivity and stage

Introduction

The role of CD3−CD56+ natural killer (NK) cells in granulomatosis with polyangiitis (GPA) is poorly understood. Recently, it has been shown that peripheral blood NK cells can kill renal microvascular endothelial cells, suggesting a pathogenic role of NK cells in this disease. So far, subset distribution, phenotype, and function of peripheral blood NK cells in relation to GPA disease activity have not been elucidated. Moreover, it is not known whether NK cells infiltrate GPA tissue lesions.

Methods

Paraffin sections of GPA granulomas and controls were stained with anti-CD56 and anti-CD3 antibodies. Peripheral blood lymphocyte subsets were analyzed by flow cytometry. NK cell degranulation was analyzed using cocultures of patient PBMCs with target cells and surface expression of CD107a. Clinical data were extracted from medical records. Statistical analysis was performed in an exploratory way.

Results

CD56+ cells were not detectable in active granulomatous GPA lesions but were found frequently in granulomas from tuberculosis and sarcoidosis patients. In GPA, the proportion of NK cells among peripheral blood lymphocytes correlated negatively with the Birmingham Vasculitis Activity Score (BVAS) (n = 28). Accordingly, NK cell percentages correlated positively with the duration of remission (n = 28) and were significantly higher in inactive GPA (BVAS = 0, n = 17) than in active GPA, healthy controls (n = 29), and inactive control diseases (n = 12). The highest NK cell percentages were found in patients with long-term remission and tapered immunosuppressive therapy. NK cell percentages >18.5 % of peripheral blood lymphocytes (n = 12/28) determined GPA inactivity with a specificity of 100 %. The differentiation into CD56^dim and CD56^bright NK cell subsets was unchanged in GPA (n = 28), irrespective of disease activity. Similar surface expression of the activating NK cell-receptors (NKp30, NKp46, and NKG2D) was determined. Like in healthy controls, GPA NK cells degranulated in the presence of NK cell receptor ligand bearing epithelial and lymphatic target cells.

Conclusions

NK cells were not detectable in GPA granulomas. Peripheral blood NK cell percentages positively correlate with the suppression of GPA activity and could serve as a biomarker for GPA activity. Peripheral blood NK cells in GPA patients are mature NK cells with preserved immune recognition.

First steps in the standardization of immunoglobulin IgG myeloperoxidase-anti-neutrophil cytoplasmic antibody measurements

The standardization of immunoassays for immunoglobulin (Ig)G myeloperoxidase-anti-neutrophil cytoplasmic antibodies (MPO-ANCA) could contribute to a more accurate diagnosis and follow-up of small vessels-associated vasculitis, a systemic autoimmune disorder that leads to necrosis of blood vessel walls. Despite significant efforts by different groups, the level of comparability of results from commercially available immunoassays used for IgG MPO-ANCA detection is still poor. Therefore, the potential for improvement using reference materials was assessed. The evaluation of a set of 30 patient samples with 11 assays showed that differences between assays result in different interpretations for individual patients. Only 10 of 30 patient samples had the same clinical interpretation among 11 assays applying the cut-off values provided by each respective manufacturer. The correlation between results from 13 different assays was assessed in a pairwise manner. The correlation between results from patient samples was systematically very good for combinations of seven of those assays. The correlation of results ranged from reasonable to good for combinations with four other assays, therefore it should be possible to improve the comparability of results using a commutable reference material for calibration. Feasibility studies were conducted in order to find a reference material format most suitable for a calibrator. Two sets of candidate reference materials were produced from different raw materials, and assessed according to their suitability. A final format was selected, and a candidate reference material was produced.

CanVasc Recommendations for the Management of Antineutrophil Cytoplasm Antibody-associated Vasculitides

Objective.

The Canadian Vasculitis research network (CanVasc) is composed of physicians from different medical specialties and researchers with expertise in vasculitis. One of its aims is to develop recommendations for the diagnosis and management of antineutrophil cytoplasm antibody (ANCA)-associated vasculitides (AAV) in Canada.

Methods.

Diagnostic and therapeutic questions were developed based on the results of a national needs assessment survey. A systematic review of existing non-Canadian recommendations and guidelines for the diagnosis and management of AAV and studies of AAV published after the 2009 European League Against Rheumatism/European Vasculitis Society recommendations (publication date: January 2009) until November 2014 was performed in the Medline database, Cochrane library, and main vasculitis conference proceedings. Quality of supporting evidence for each therapeutic recommendation was graded. The full working group as well as additional reviewers, including patients, reviewed the developed therapeutic recommendations and nontherapeutic statements using a modified 2-step Delphi technique and through discussion to reach consensus.

Results.

Nineteen recommendations and 17 statements addressing general AAV diagnosis and management were developed, as well as appendices for practical use, for rheumatologists, nephrologists, respirologists, general internists, and all other healthcare professionals more occasionally involved in the management of patients with AAV in community and academic practice settings.

Conclusion.

These recommendations were developed based on a synthesis of existing international guidelines, other published supporting evidence, and expert consensus considering the Canadian healthcare context, with the intention of promoting best practices and improving healthcare delivery for patients with AAV.

Linking classification and therapeutic management of vasculitides

Vasculitides are classified by the size, type and location of the predominantly involved vessels and by their primary or secondary nature. Their treatment depends on the type of vasculitis, its etiology (when known), and its severity and must be further adjusted by the individual characteristics and comorbidities of patients. In this paper, we review how the classification and definition of vasculitides have evolved over the past years and how it has affected therapeutic changes. As new genetic markers are being discovered and the pathogenesis of vasculitides continues to be elucidated, further modifications in classification and treatment can be expected.

Role of autoantibody testing

Autoantibodies are the serological hallmark of autoimmune disease. Though their pathogenic role is debatable, they play an important role in the management of a patient with rheumatic disease. However, due to their presence in the general population as well as in multiple autoimmune diseases, the presence of an autoantibody alone does not make a diagnosis; the result has to be interpreted along with clinical findings. Similarly, the absence of autoantibody does not exclude a disease. The common autoantibodies used in clinical practice include rheumatoid factor, anti-CCP antibodies, antinuclear antibodies (ANAs), anti-neutrophil cytoplasmic antibodies (ANCA) and anti-phospholipid antibodies. Once an autoantibody to a broad antigen is detected in a patient, sub-specificity analysis can improve the utility of the antibody. Autoantibodies are detected in the serum using different assays and results of which can vary; thus, it is important for a clinician to know the method used, its sensitivity and specificity to help in the proper interpretation of the laboratory results. This review will address these issues.

Microscopic polyangiitis: Advances in diagnostic and therapeutic approaches

Microscopic polyangiitis (MPA) is an idiopathic autoimmune disease characterized by systemic vasculitis. The disease predominantly affects small-calibre blood vessels and is associated with the presence of antineutrophil cytoplasmic autoantibodies (ANCA). Microscopic polyangiitis was considered to be a disease entity by Savage et al. in 1985. Microscopic polyangiitis has a reported low incidence and a slight male predominance. The aetiology of MPA remains unknown. There is, however, increased evidence that MPA is an autoimmune disease in which ANCAs, particularly those reacting with MPO, are pathogenic. MPA belongs to the systemic vasculitides, indicating that multiple organs can be affected. The major organs involved in MPA are the kidneys and the lungs. As expected for an illness that affects multiple organ systems, patients with MPA can present with a myriad of different symptoms. Ear, nose and throat (ENT) manifestations are not considered to be clinical symptoms of MPA, but in the majority of populations described, ENT involvement was found in surprisingly high percentages. MPA is part of the ANCA-associated vasculitides, which are characterized by necrotizing vasculitis of small vessels. Diagnosis is mainly established by clinical manifestations, computed tomography (TC), ANCA antibody detection and renal and pulmonary biopsy. The introduction of aggressive immunosuppressive treatment has substantially improved the prognosis. The standardized therapeutic regimen is based on cyclophosphamide and corticosteroids. Using this regimen, remission can be achieved in most of the patients. Rituximab may represent an important alternative to cyclophosphamide for patients who may not respond adequately to antimetabolite therapies.

Myeloperoxidase-antineutrophil Cytoplasmic Antibodies (MPO-ANCA) and Proteinase 3-ANCA without Immunofluorescent ANCA Found by Routine Clinical Testing

OBJECTIVE

Concurrent testing for serum antineutrophil cytoplasmic antibodies (ANCA) by indirect immunofluorescence (IF) and by antiproteinase 3 (PR3)/antimyeloperoxidase (MPO) antibody assays may identify patients with PR3-ANCA or MPO-ANCA despite a negative IF (IF-negative MPO/PR3-positive); however, the significance of this result is not clear. We sought to determine whether IF-negative, MPO/PR3-positive results identified any cases of clinically meaningful systemic vasculitis at our institution.

METHODS

We conducted a retrospective chart review of all IF-negative, MPO/PR3-positive patients identified at our institution over a 2-year period.

RESULTS

Of the 2345 samples tested over 2 years, 1998 were IF-negative. Among these IF-negative samples, 49 samples (2.5%) derived from 38 patients tested positive for MPO-ANCA or PR3-ANCA. Only 1 IF-negative, MPO/PR3-positive patient was subsequently diagnosed with ANCA-associated vasculitis (AAV). Eleven IF-negative, MPO/PR3-positive patients (29%) had been previously diagnosed and treated for AAV, all with positive IF and antibody tests prior to treatment. Four patients had evidence of cutaneous vasculitis not attributed to AAV, while several of the remaining IF-negative, MPO/PR3-positive patients had other immunologic disorders, including systemic lupus erythematosus (5 patients) and inflammatory bowel disease (3 patients).

CONCLUSION

In this real-life cohort assayed simultaneously by IF and multiplexed bead assays, the detection of MPO-ANCA or PR3-ANCA without a positive IF rarely led to a new diagnosis of systemic vasculitis, and was more likely to occur in the context of a non-vasculitic inflammatory condition. Our results suggest that concurrent IF and MPO/PR3 testing may be of limited use in preventing a missed diagnosis of new-onset AAV.

Clinical aspects of indirect immunofluorescence for autoimmune diseases

Because the most common term used in conversations considering autoimmunity is autoantibodies, it is well-expected that the indirect immunofluorescence assay, which detects antibodies directed against various antigens, is one of our most impressive techniques for investigating autoimmune diseases (AIDs). Roughly speaking, the current literature corroborates that this immunopathologic investigation means that autoantibodies detection makes a considerable contribution to both diagnostic and prognostic aspects of AIDs in the clinical setting. However, it varies between different AIDs, autoantibodies, ethnicities or detection methodologies. Directly focusing on the indirect immunofluorescence assay, we present evidence to support this multidimensional variation regarding the subject via reviewing briefly the best-investigated autoantibodies in the well-documented AIDs, including vasculitis, inflammatory bowel disease, scleroderma, autoimmune hepatitis, primary biliary cirrhosis, systemic lupus erythematosus and Sjögren's syndrome.

Pathogenesis of anti-neutrophil cytoplasmic antibody-associated vasculitis: challenges and solutions 2014

Anti-neutrophil cytoplasmic autoantibodies (ANCA) with specificity for proteinase 3 (PR3-ANCA) or myeloperoxidase (MPO-ANCA) are a defining feature of ANCA-associated vasculitides (AAV). They play a pivotal role in disease pathophysiology and have strongly improved early diagnosis and treatment of these infrequent, but potentially fatal diseases. Neutrophils and their products are major players in initiating the autoimmune response and tissue destruction in vasculitic as well as granulomatous inflammation. This review highlights recent findings on old and novel players (ANCA, neutrophils, neutrophil extracellular traps, fibroblasts, immune cells and complement) and puts them into context with the current understanding of disease mechanisms in AAV.