Detection Of Antineutrophil Cytoplasmic Antibodies Research Articles

On the problem of differential diagnosis in the detection of antineutrophil cytoplasmic antibodies

Vasculitides associated with antineutrophil cytoplasmic antibodies (ANCA) are a group of systemic autoimmune diseases characterized by necrotizing lesions of the walls of predominantly small vessels and the presence of ANCA against proteinase 3 or myeloperoxidase. However, an increase in ANCA levels can also be observed in other diseases, including autoimmune, malignant and infectious diseases, which complicates the interpretation of clinical and laboratory data and requires a differential diagnosis.

Comparison of the Capacity of Several Machine Learning Tools to Assist Immunofluorescence-Based Detection of Anti-Neutrophil Cytoplasmic Antibodies.

The success of artificial intelligence and machine learning is an incentive to develop new algorithms to increase the rapidity and reliability of medical diagnosis. Here we compared different strategies aimed at processing microscope images used to detect anti-neutrophil cytoplasmic antibodies, an important vasculitis marker: (i) basic classifier methods (logistic regression, k-nearest neighbors and decision tree) were used to process custom-made indices derived from immunofluorescence images yielded by 137 sera. (ii) These methods were combined with dimensional reduction to analyze 1733 individual cell images. (iii) More complex models based on neural networks were used to analyze the same dataset. The efficiency of discriminating between positive and negative samples and different fluorescence patterns was quantified with Rand-type accuracy index, kappa index and ROC curve. It is concluded that basic models trained on a limited dataset allowed for positive/negative discrimination with an efficiency comparable to that obtained by conventional analysis performed by humans (0.84 kappa score). More extensive datasets and more sophisticated models may be required for efficient discrimination between fluorescence patterns generated by different auto-antibody species.

Wegener's granulomatosis: difficulties in diagnosis and treatment

Granulomatosis with polyangiitis (Wegener's granulomatosis, GPA) is a rare disease of unknown etiology with multiple organ lesions, characterized by the development of necrotizing granulomatous inflammation and signs of autoimmune vasculitis, predominantly affecting small and medium-sized vessels. In the above clinical case, the patient has a classic triad of symptoms (damage to the upper respiratory tract, lungs, kidneys), the diagnosis was confirmed morphologically. The peculiarity of the described clinical case is its rare prevalence, the difficulty in making a diagnosis due to the multiorganism of the lesion, the absence of specific signs at the onset of the disease, which required a differential diagnosis. Early detection of antineutrophil cytoplasmic antibodies (ANCA) in the blood increases the frequency of GPA diagnosis, and timely diagnosis allows prescribing therapy as soon as possible and avoiding disability in patients.

Eosinophilic granulomatosis with polyangiitis: etiopathogenesis, classification and clinical phenotypes

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare systemic disease that can be classified as both a hypereosinophilic condition and an antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis and is characterized by granulomatous inflammation. The pathogenesis of EGPA is not completely understood. It is likely that this disease is Th2-mediated, and blood and tissue eosinophilia serves as the main diagnostic criterion. The hallmarks and main effectors of organ damage in EGPA include asthma-associated necrotizing vasculitis of small-to-medium vessels and eosinophilic proliferation. Endothelial injury and vascular inflammation in EGPA is caused by ANCA via activation of circulating neutrophils. Two clinical phenotypes of the disease have been described based on the detection of ANCA: ANCA-negative with manifestations of hypereosinophilia (for example, pulmonary infiltrates and cardiomyopathy) and ANCA-positive with clinical signs of vasculitis (for example, glomerulonephritis, purpura, and mononeuritis multiplex). Both phenotypes were confirmed by histological and genomic research. However, these two coexisting mechanisms cannot be separated in clinical practice.The aim of the article is to present current knowledge of eosinophilic and ANCA-mediated aspects of the pathogenesis, classification and clinical phenotypes of EGPA, and consider prospects for future research.Conclusion. The development of EGPA is based on eosinophilic dysfunction. This dysfunction means that patients with a genetically determined predisposition to recognize the ANCA antigen and with HLA-DQ (human leukocyte antigen DQ) alleles produce anti-myeloperoxidase autoantibodies and later develop an aberrant autoimmune process. Further comprehensive post-genomic studies are needed to identify the pathogenetic mechanisms and characterize molecular features of EGPA clinical phenotypes. The elaboration of molecular endotypes will lead to the identification of new activity biomarkers and therapeutic targets that can improve the diagnosis of EGPA and the treatment outcomes.

PR3-ANCAs Detected by Third-Generation ELISA Predicts Severe Disease and Poor Survival in Primary Sclerosing Cholangitis.

A highly sensitive detection of anti-neutrophil cytoplasmic antibodies to serine proteinase-3 (PR3-ANCAs) aids in the serological diagnosis of autoimmune liver disorders and the prediction of severity in primary sclerosing cholangitis (PSC). Here, we evaluate a novel third-generation ELISA for the detection of PR3-ANCAs. In total, 309 patients with PSC, 51 with primary biliary cholangitis (PBC), and 120 healthy blood donors (BD) were analyzed. For the survival analysis in PSC, the outcome was defined as liver-transplantation-free survival during the follow-up. Positive PR3-ANCA levels were found in 74/309 (24.0%) of patients with PSC. No BDs and one patient with PBC demonstrated PR3-ANCA positivity. PR3-ANCAs were revealed as independent predictors for a poor PSC outcome (study endpoint: liver transplantation/death, log-rank test, p = 0.02). PR3-ANCA positivity, lower albumin levels, and higher bilirubin concentrations were independent risks of a poor survival (Cox proportional-hazards regression analysis, p < 0.05). The Mayo risk score for PSC was associated with PR3-ANCA positivity (p = 0.01) and the disease severity assessed with a model of end-stage liver disease (MELD) and extended MELD-Na (p < 0.05). PR3-ANCAs detected by a third-generation ELISA are diagnostic and prognostic markers for PSC. Their wider use could help to identify patients who are at-risk of a more severe disease.

Value of combined detection of PCA, ANCA, ASCA, AGA and ANA in early diagnosis of Gastrointestinal Diseases.

ABSTRACTObjectives:To investigate the positive detection rate and clinical application value of anti-parietal cell antibody (PCA), anti-neutrophil cytoplasmic antibody (ANCA), anti-Saccharomyces cerevisiae antibody (ASCA), anti-gliadin antibody (AGA) and anti-nuclear antibody (ANA) in patients visiting the Department of Gastroenterology.Methods:From January 2015 to June 2018, 1,083 patients receiving detection of PCA and other autoantibodies were selected from the Department of Gastroenterology of Baoding First Central Hospital. The positive detection rate of autoantibodies was statistically analyzed. The enumeration data were expressed as rate or constituent ratio, and the rates were compared between groups using the x2 test.Results:Among the 1,083 patients, the positive detection rate of ANA, ASCA, AGA, PCA and ANCA was 33.52%, 16.71%, 15.51%, 13.66% and 7.66%, respectively. The total positive detection rate was 62.8% (n = 680).Conclusion:The population with abdominal distension, chronic abdominal pain, diarrhea and other digestive system symptoms should be timely treated with combined detection of PCA, ANCA, ASCA, AGA and ANA, which is of important clinical application value for early diagnosis of gastrointestinal diseases and prevention of missed diagnosis and misdiagnosis.

A clinical case of lung damage in granulomatosis with polyangiitis

The article presents a case of granulomatosis with polyangiitis, which is difficult for clinical diagnosis. Recently, the incidence of systemic vasculitis has increased, and given the similarity of clinical symptoms with other pathologies, a doctor of any specialty should carry out differential diagnosis. Granulomatosis with polyangiitis is characterized mainly by damage to the upper respiratory tract, lungs, and kidneys. The main method for diagnosing granulomatosis with polyangiitis is biopsy with histological examination, which allows to detect inflammation in the affected tissues. A feature of granulomatosis with polyangiitis is detection of antineutrophil cytoplasmic antibodies in the blood serum. However, these antibodies are recorded only in 80% of patients and are not detected in the remission phase, which makes diagnosis much more difficult.

Neutrophil fixation protocols suitable for substrates to detect anti-neutrophil cytoplasmic antibodies by indirect immunofluorescence

Anti-neutrophil cytoplasmic antibodies (ANCAs) are autoantibodies that recognize neutrophil cytoplasmic antigens. The major ANCA antigens are myeloperoxidase and proteinase 3. Necrotizing small vessel vasculitis accompanied by ANCA production is called ANCA-associated vasculitis (AAV). In addition to AAV, ANCA is sometimes produced in patients with connective tissue diseases, such as systemic lupus erythematosus, and inflammatory bowel diseases. Indirect immunofluorescence (IIF) and enzyme immunoassay (EIA) have been used to detect ANCAs. Recently, the accuracy of EIA has improved and it has become the gold standard for ANCA detection. However, IIF does not lose its role in ANCA detection because EIA cannot detect ANCAs that recognize antigens other than those coated on the plate. For IIF, neutrophil substrates prepared with two different fixations, namely, ethanol fixation and formalin fixation, are used. There is a recommended protocol for ethanol fixation but not for formalin fixation. This study prepared neutrophil substrates according to the recommended protocol for ethanol fixation and protocols in the literature and original protocols for formalin fixation and then examined ANCA specificity and how storage period would influence the number of cells, antigen distribution, and antigenicity of the substrates. As a result, the number of cells and antigen distribution did not change after storage for up to 2 months regardless of fixation protocols, whereas a time-dependent decline in ANCA antigenicity and a fixation protocol-dependent difference in ANCA specificity were observed. How neutrophils are fixed on the glass slide needs to be checked upon evaluation of ANCAs by IIF.

Antineutrophil Cytoplasmic Antibodies in Patients Treated With Methimazole

Abstract Introduction: Antithyroid drugs (ATDs) are widely used for the treatment of hyperthyroidism. Most side effects of these medications are mild and emerge within the first months of treatment. In contrast, antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis is a severe adverse event whose occurrence increases with increasing time of treatment. Vasculitis is more frequently associated with propylthiouracil than with methimazole, but the latter has also been related to the occurrence of ANCA and even to clinically manifest vasculitis. Many patients develop ANCA during treatment with methimazole but do not exhibit signs/symptoms of vasculitis. Objective: We previously reported a relatively high frequency (20%) of ANCA in patients exposed to methimazole but none of them exhibited clinical manifestations of vasculitis on that occasion. We continued to follow up these patients with ANCA and report here their evolution after 2 years. Methods: Seventeen patients exposed to methimazole were followed for 2 years after antibodies detection (ANCA). Results: Eight patients had ANCA but had not used methimazole for at least 6 months. During the following 24 months, continuing without ATD, none of the patients developed clinically apparent vasculitis. In the last assessment, five patients no longer had ANCA, while these antibodies persisted in three. Nine patients had ANCA and had been on methimazole for at least 6 months. The medication was not immediately discontinued in these patients when the antibodies were detected. After this detection, treatment with methimazole was continued in these patients for more 3 months (n = 1), 6 months (n = 2), 9 months (n = 1), 12 months (n = 2), 18 months (n = 2), and 24 months (n = 1). During the 2 years of follow-up after the detection of ANCA, none of the 9 patients developed signs/symptoms of vasculitis. In the last assessment, ANCA were negative in two patients who had received methimazole for more 3 and 6 months and who were therefore without receiving the drug for 21 and 18 months, respectively. The other 7 patients remained ANCA positive. Conclusion: Although vasculitis is necessarily associated with the presence of ANCA, the inverse frequency is undefined and appears to be low. Thus, measurement of ANCA would not be recommended in asymptomatic patients during methimazole treatment and immediate discontinuation of this drug, if these antibodies are detected eventually, may not be required. Reference: Antineutrophil cytoplasmic antibodies in patients treated with methimazole: a prospective Brazilian study. Andrade GC, Maia FCP, Mourão GF, Rosario PW, Calsolari MR. Braz J Otorhinolaryngol. 2019; 85:636-41.

Temporal Arteritis Revealing Antineutrophil Cytoplasmic Antibody-Associated Vasculitides: A Case-Control Study.

Temporal arteritis (TA) is a typical manifestation of giant cell arteritis (GCA). Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are rarely revealed by TA manifestations, leading to a risk of misdiagnosis of GCA and inappropriate treatments. This study was undertaken to describe the clinical, biologic, and histologic presentations and outcomes in cases of TA revealing AAV (TA-AAV) compared to controls with classic GCA. In this retrospective case-control study, the characteristics of patients with TA-AAV were compared to those of control subjects with classic GCA. Log-rank test, with hazard ratios (HRs) and 95% confidence intervals (95% CIs), was used to assess the risk of treatment failure. Fifty patients with TA-AAV (median age 70 years) were included. Thirty-three patients (66%) presented with atypical symptoms of GCA (ear, nose, and throat involvement in 32% of patients, and renal, pulmonary, and neurologic involvement in 26%, 20%, and 16% of patients, respectively). Blood samples were screened for ANCAs at the time of disease onset in 33 patients, and results were positive in 88%, leading to a diagnosis of early TA-AAV in 20 patients. The diagnosis of AAV was delayed a median interval of 15 months in 30 patients. Compared to controls with GCA, patients with TA-AAV were younger (median age 70 years versus 74 years), were more frequently men (48% versus 30%), and had high frequencies of atypical manifestations and higher C-reactive protein levels (median 10.8 mg/dl versus 7.0 mg/dl). In patients with TA-AAV, temporal artery biopsy (TAB) showed fibrinoid necrosis and small branch vasculitis in 23% of patients each, whereas neither of these characteristics was evident in controls with GCA. Treatment failure-free survival was comparable between early TA-AAV cases and GCA controls, whereas those with delayed TA-AAV had a significantly higher risk of treatment failure compared to controls (HR 3.85, 95% CI 1.97-7.51; P < 0.0001). TA-AAV should be considered diagnostically in cases of atypical manifestations of GCA, refractoriness to glucocorticoid treatment, or early relapse. Analysis of TAB specimens for the detection of small branch vasculitis and/or fibrinoid necrosis could be useful. Detection of ANCAs should be performed in cases of suspected GCA with atypical clinical features and/or evidence of temporal artery abnormalities on TAB.

Evaluation of the diagnostic performance of an immunoblot for ANCA and anti-GBM antibody detection

The use of high-quality antigen-specific immunoassays for detecting anti-neutrophil cytoplasmic antibodies (ANCA) and anti-glomerular basement membrane (GBM) autoantibodies is recommended in patients with suspected ANCA vasculitis and/or anti-GBM disease. We analysed the diagnostic performance of a semi-quantitative and rapid immunoblot (EUROIMMUN AG, Lübeck, Germany) in two settings. Patient sera from different cohorts (ANCA vasculitis n = 187, anti-GBM disease n = 19, and disease controls n = 51) were used. The diagnostic performance of the immunoblot was assessed when used as a confirmatory test for the presence of ANCA in suspected ANCA vasculitis and when evaluating the presence of ANCA and/or anti-GBM antibodies in AAV and/or anti-GBM disease patients with a rapidly progressive glomerulonephritis (RPGN). In a confirmatory test setting, the immunoblot had an optimal sensitivity and specificity of 97.4 and 98.1% for PR3-ANCA and 98.5 and 96.4% for MPO-ANCA, respectively. With increasing test result ranges, a higher interval likelihood ratio (LR) was found for both ANCA entities. When evaluating for ANCA in patients with RPGN, the highest diagnostic accuracy (sensitivity 92.9% and specificity 100%) was obtained by using different cut-off values of positivity for PR3- (>5) and MPO-ANCA (>10). Also, the diagnostic performance for detecting anti-GBM was good (sensitivity 100% and specificity 100%). There are advantages over other assays in terms of time, costs, and interpretation of results. The immunoblot is a useful addition to current guidelines, particularly when a rapid diagnosis is necessary.

ANCA diagnostics in vasculitis

The cornerstone of the laboratory diagnostics of small vessel vasculitis is the detection of antineutrophil cytoplasmic antibodies (ANCA). The current international consensus recommendations suggest that proteinase 3 (PR3) and myeloperoxidase (MPO) ANCA immunoassays should be used as afirst-line test if there is a justified suspicion of ANCA-associated vasculitis (AAV). A second method is only recommendable when the immunoassay shows a negative or borderline result. The precise identification of all patients with active AAV and avoidance of misdiagnoses due to false positive ANCA measurements is achieved when the ANCA determination is limited to defined clinical situations, which are indicative for AAV. There is increasing evidence that the specificity of ANCA to define homogeneous groups of patients could be better with respect to the prognosis than the clinical subtype.

P181 Detection of anti-neutrophil cytoplasmic antibodies: a single-centre evaluation of the value of indirect immunofluorescence versus antigen-specific immunoassays

Abstract Background Anti-neutrophil cytoplasmic antibodies (ANCAs) are valuable laboratory markers used for the diagnosis of medium and small-vessel vasculitis, including granulomatosis with polyangiitis (GPA), eosinophilic granulomatosis with polyangiitis (EGPA) and microscopic polyangiitis (MPA). According to the 1999 international consensus, indirect immunofluorescence (IIF) should be used to screen for ANCAs; samples containing ANCAs should then be tested by immunoassays for proteinase 3 (PR3)-ANCAs and myeloperoxidase (MPO)-ANCAs. As dependable immunoassays for PR3ANCAs and MPO-ANCAs have become broadly available, there is increasing agreement that high-quality immunoassays are the preferred screening method for the diagnosis of ANCA-associated vasculitis (AAV). This single centre study was performed to evaluate the accuracy of MPO and PR3 immunoassays in comparison to IIF in the diagnosis of AAV. Methods We retrospectively reviewed the clinical information of patients that underwent ANCA testing between 1/6/19-30/6/19, via our electronic web portal. Data collected included patients’ demographics, ANCA /MPO/PR3 result, and diagnosis as established by their treating physician. A total of 403 ANCA requests were submitted to the Immunology Department at the Royal Wolverhampton NHS Trust. We excluded 55 patients with insufficient information. Due to multiple ANCA tests in a single patient we included only the first test request. Therefore, the study population includes 345 patients. IIF at our centre is performed for all ANCA requests using a commercially available ASP1200 automated dilutor to process the IIF slides with Werfen (Inova) ANCA slides. For the detection of antibodies against MPO and PR3 a commercially available immuno-assay Phadia-250 ImmunoCAP analyser is used in patients with positive IIF. Diagnostic performance was assessed using sensitivity and specificity. Results The proportion of ANCA negative patients by IIF (177 patients,51.3%) was almost identical to that of the ANCA positive group (168 patients,48.7%). Only 13 patients (3.8%) received a diagnosis of AAV. Of the ANCA positive patients 12 (7.1%) had an AAV. 6 of the 13 patients with vasculitis had a supportive tissue biopsy. One ANCA negative patient and one ANCA positive MPO/PR3 negative patient had a diagnosis of vasculitis, previously diagnosed and now on steroid treatment; both were ANCA and MPO positive at diagnosis. 15 patients were MPO or PR3 positive, 11/15 had a diagnosis of vasculitis (73%). Our data found IIF has a sensitivity of 91.67%, specificity 53.01% for detection of AAV. In comparison immunoassay was found to have a sensitivity of 91.67% and specificity of 97.44%. Conclusion ANCAs are helpful in the diagnosis of AAV, but their use as a diagnostic biomarker should be undertaken in the appropriate clinical context. Immunoassay has a superior diagnostic performance at our centre. Our data suggests screening for ANCA with IIF is not of added value when using high-quality antigen-specific immunoassays. Disclosures N. Cleaton None. T. Adizie None. N. Barkham None.

The Diagnostic and Clinical Utility of Autoantibodies in Systemic Vasculitis

Considerable progress has been made in understanding the role of autoantibodies in systemic vasculitides (SV), and consequently testing for anti-neutrophil cytoplasmic antibodies (ANCA), anti-glomerular basement membrane antibodies (anti-GBM), and anti-C1q antibodies is helpful and necessary in the diagnosis, prognosis, and monitoring of small-vessel vasculitis. ANCA-directed proteinase 3 (PR3-) or myeloperoxidase (MPO-) are sensitive and specific serologic markers for ANCA-associated vasculitides (AAV), anti-GBM antibodies are highly specific for the patients with anti-GBM antibody disease (formerly Goodpasture’s syndrome), and autoantibodies to C1q are characteristic of hypocomlementemic urticarial vasculitis syndrome (HUVS; anti-C1q vasculitis). The results of a current EUVAS study have led to changes in the established strategy for the ANCA testing in small-vessel vasculitis. The revised 2017 international consensus recommendations for ANCA detection support the primary use PR3- and MPO-ANCA immunoassays without the categorical need for additional indirect immunofluorescence (IIF). Interestingly, the presence of PR3- and MPO-ANCA have led to the differentiation of distinct disease phenotype of AAV: PR3-ANCA-associated vasculitis (PR3-AAV), MPO-ANCA-associated vasculitis (MPO-AAV), and ANCA-negative vasculitis. Further studies on the role of these autoantibodies are required to better categorize and manage appropriately the patients with small-vessel vasculitis and to develop more targeted therapy.

Detection of Anti-neutrophil Cytoplasmic Antibodies (ANCA) by Indirect Immunofluorescence.

The eventual presence of anti-neutrophil cytoplasmic antibodies (ANCA) can initially be screened with indirect immunofluorescence (IIF). The majority of laboratories that facilitate ANCA testing use commercial kits. Although in-house assays are not encouraged in routine clinical laboratories, knowledge on the methodological aspects of the assay remains of importance. These aspects include choice of substrate, choice of fixative, staining procedure, and interpretation procedure. In this paper details on the methodology are provided and discussed in the context of the clinical application.

Progress in laboratory detection of anti-neutrophil cytoplasmic antibodies

Along with the rapid development of biomedical technology and the clinical application of anti-neutrophil cytoplasmic antibody (ANCA), the detection of ANCA by indirect immunofluorescence (IIF) and the detection of specific autoantibodies of ANCA by various immunological methods have also been developed, which promoted the standardization of ANCA′s laboratory testing procedures. These advances have brought new opportunities and challenges to ANCA′s laboratory testing technology and its clinical application. (Chin J Lab Med, 2018, 41: 905-908) Key words: Antibodies, antineutrophil cytoplasmic; Autoantibodies; Fluorescent antibody technique, indirect; Clinical laboratory techniques

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

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

Detection of anti-neutrophil cytoplasmic antibodies in dogs with immune-mediated inflammatory diseases

Anti-neutrophil cytoplasmic antibody (ANCA) is a type of autoantibody against neutrophil cytoplasm. In veterinary medicine, few studies have reported the detection of ANCA in dogs, and most of these studies were performed in dogs with inflammatory bowel disease (IBD). The aim of this study was to evaluate whether ANCA is detected in dogs with immune-mediated inflammatory diseases (IMIDs) other than IBD. Serum samples were collected before treatment initiation from 40 client-owned dogs with various diseases and 22 healthy beagle dogs; the dogs were classified into two groups: IMID group (n = 16) and control group (n = 46). ANCA was detected using the indirect fluorescent antibody test. Of the 16 dogs in the IMID group, 13 (81.3%) tested positive for ANCA. In contrast, of the 46 dogs in the control group, 13 (28.03%) tested positive for ANCA. Moreover, a significant association between ANCA positivity and IMIDs was identified in the IMID group than in the control group (P = 0.0003). In the control group, however, dogs with bacterial infection showed a relatively high rate of ANCA positivity. Therefore, ANCA positivity was observed in dogs with both IMIDs and bacterial infection. This suggested that ANCA positivity is associated with diseases accompanied by neutrophil activation and infiltration.

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 cytoplasmic antibodies and their clinical significance

Anti-neutrophil cytoplasmic antibodies (ANCA) are a group of autoantibodies that cause systemic vascular inflammation by binding to target antigens of neutrophils. These autoantibodies can be found in serum from patients with systemic small-vessel vasculitis and they are considered as a biomarker for ANCA-associated vasculitis (AAV). A conventional screening test to detect ANCA in the serum is indirect immunofluorescence study, and subsequently confirmed by enzyme-linked immunosorbent assay. A positive staining of ANCA can be classified into three main categories based on the staining patterns: cytoplasmic, perinuclear, and atypical. Patients with granulomatosis with polyangiitis (GPA) mostly have a positive cytoplasmic staining pattern (c-ANCA) whilst a perinuclear pattern (p-ANCA) is more common in microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA) patients. Atypical pattern (a-ANCA) is rarely seen in patients with systemic small-vessel vasculitis but it can be found in other conditions. Here, techniques for ANCA detection, ANCA staining patterns and their clinical significances are reviewed.