Immunofluorescent patterns produced by antineutrophil cytoplasmic antibodies (ANCA) vary depending on neutrophil substrate and conjugate

Multiplexed Detection of Cancer Serum Antigens with a Quantum Dot-Based Lab-on-Bead System

A quantum dot (QD)-based lab-on-bead system is a unique tool for multiple analysis of cancer markers in human serum samples by using a flow cytometer. In terms of specificity and sensitivity, this method is comparable with ELISA, the "gold standard" of serological in-clinic detection of single analytes. Fluorescent microspheres encoded with QDs have been used for the quantitative detection of free and total prostate-specific antigen in human serum samples. Developed multiplex assay demonstrates a clear discrimination between serum samples from control subjects and cancer patients. The proposed QD-based method is adaptable and makes it possible to develop numerous clinical tests with decreased duration and cost for early diagnosis of various diseases.

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.

PR3-ANCA: a promising biomarker in primary sclerosing cholangitis (PSC)

Background and Aims

The only recognized biomarker for primary sclerosing cholangitis (PSC) is atypical anti-neutrophil cytoplasmic antibodies (aANCA), which, in addition to having low sensitivity and specificity, is an indirect immunofluorescence (IIF) test lacking the advantages of high throughput and objectivity. Recent reports have shown that antibodies to proteinase-3 (PR3-ANCA) might add diagnostic value in inflammatory bowel disease (IBD), specifically in ulcerative colitis (UC). As PSC is associated with IBD, the objective of this study was to evaluate the frequency and clinical significance of PR3-ANCA in a large cohort of patients.

Methods

A total of 244 PSC and 254 control [autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), hepatitis C viral infection (HCV), hepatitis B viral infection (HBV), and healthy controls] sera and their clinical correlations were retrospectively analyzed for PR3-ANCA determined by ELISA and a new chemiluminescence immunoassay (CIA). Testing was also performed for aANCA by IIF.

Results

When measured by CIA, PR3-ANCA was detected in 38.5% (94/244) of PSC patients compared to 10.6% (27/254) controls (p<0.0001). By ELISA, PR3-ANCA was detected in 23.4% (57/244) of PSC patients compared to 2.7% (6/254) controls (p<0.0001). PR3-ANCA in PSC patients was not associated with the presence or type of underlying IBD, and, in fact, it was more frequent in Crohn's disease (CD) patients with PSC than previously reported in CD alone. PR3-ANCA in PSC measured by CIA correlated with higher liver enzymes.

Conclusion

PR3-ANCA is detected in a significant proportion of PSC patients compared to other liver diseases including PBC and AIH. PR3-ANCA is associated with higher liver enzyme levels in PSC, and is not solely related to underlying IBD.

C-ANCA/proteinase 3-positive colitis in children: a distinctive form of inflammatory bowel disease or vasculitis with colitis as initial presentation?

AIM

Anti-neutrophil cytoplasmic antibodies (ANCAs) detected by indirect immunofluorescence have been found in patients with inflammatory bowel disease (IBD). Nevertheless, specific antibodies against proteinase-3 (PR3) are rare in this context.

METHODS

Sera from 30 consecutive pediatric patients with IBD were evaluated for ANCA-indirect immunofluorescence and its specific antibodies to investigate whether PR3-ANCA positivity (PR3-ANCA+) identifies a distinct IBD subtype.

RESULTS

The 5 PR3-ANCA+ patients (17%) showed significantly more concomitant biliary disease and severe anal blood loss (P < 0.05). None had vasculitis features at diagnosis nor during follow-up.

CONCLUSIONS

This pilot study demonstrates significant clinical differences between the PR3-ANCA-positive and -negative IBD subset.

Antineutrophil cytoplasmic antibody (ANCA) testing of routine sera varies in different laboratories but concordance is greater for cytoplasmic fluorescence (C-ANCA) and myeloperoxidase specificity (MPO-ANCA)

Most laboratories screen for antineutrophil cytoplasmic antibodies (ANCA) with indirect immunofluorescence (IIF) and confirm cytoplasmic (C-ANCA) and perinuclear (P-ANCA) staining with ELISAs for proteinase 3 (PR3) and myeloperoxidase (MPO) specificities. This study determined the concordance of ANCA test results from 48 diagnostic laboratories participating in a national Quality Assurance programme, that used different assays and methods and varied in expertise. Laboratories were circulated with a questionnaire about their techniques, and provided with 24 sera for testing over a 30 month period. Results for individual sera were compared with the 'observed consensus' found in more than 50% of laboratories. The 23 laboratories (48%) that responded to the questionnaire used 5 different IIF substrates and 11 ELISAs, and differed in other aspects of testing. Concordance for ANCA test results was greater for IIF-positive (n=22, median 96%, range 68%-100%) than an IIF-negative serum (median 64%); for C-ANCA (n=8, median 89%, range 66-100%) rather than P-ANCA (n=10, median 76%, range 52-88%); for MPO-ANCA (n=5, median 100%) rather than PR3-ANCA (n=7, median 89%, range 82-100%); and for strongly-positive (n=2, median 97%, range 96-97%) rather than low positive PR3-ANCA (n=4, median 80%, range 74-86%). Concordance for test results might be improved with further standardisation of testing methodologies.

Nanocrystal-encoded fluorescent microbeads for proteomics: antibody profiling and diagnostics of autoimmune diseases

The first application of nanocrystal (NC)-encoded microbeads to clinical proteomics is demonstrated by multiplexed detection of circulating autoantibodies, markers of systemic sclerosis. Two-color complexes, consisting of NC-encoded, antigen-covered beads, anti-antigen antibody or clinical serum samples, and dye-tagged detecting antibodies, were observed using flow cytometry assays and on the surface of single beads. The results of flow cytometry assays correlated with the ELISA technique and provided clear discrimination between the sera samples of healthy donors and patients with autoimmune disease. Microbead fluorescence signals exhibited narrow distribution regardless of their surface antigen staining, without the need of any fluorescence compensation-a parameter determining the limit of sensitivity of flow cytometry assays. In single bead measurements, less than 30 dye-labeled antibodies interacting with the topoI-specific antibodies at the surface of a bead have been detected by the emission of dye excited through the FRET from NCs. In this format, the antibody-bead interaction reaction turns specifically the fluorescence signal from dye label off and on, additionally increasing autoantibody detection sensitivity.

Comparison of a multiplex, bead-based fluorescent assay and immunofluorescence methods for the detection of ANA and ANCA autoantibodies in human serum

Detection of antinuclear (ANA) and antineutrophil cytoplasmic (ANCA) antibodies is extensively used for establishing a diagnosis in patients with clinical features suggestive of autoimmune disorders. The most common methods for the identification of positive patients' sera for ANA or ANCA are indirect immunofluorescence (IIF) and ELISA-based procedures. Considerable effort has been made in developing simpler automated assays for routine laboratory use. Recently a commercially available microsphere-based fluorescent assay has been introduced for the detection of ANA and ANCA. The aim of this study was to compare this technology with routinely used IIF and ELISA procedures, in patients with a suggested autoimmune disorder. A highly significant correlation between ELISA procedures for specific antibodies and the microsphere-based assays were obtained for both ANA and ANCA as well as for extractable nuclear antigens ELISA screening, indicating that multiplex technology could replace individual ELISA tests for the measurement of specific autoantibodies. However, a low sensitivity for identifying IIF-positive cases was obtained for both ANA (58.0%) and ANCA (59.1%), although there was a significant correlation between the assays. In conclusion, our data show that a microsphere-based fluorescent assay may be a valid platform for the simultaneous determination of circulating individual ANA and ANCA autoantibodies. Furthermore, multiplexing technology offers several advantages that will probably make it an attractive tool in the future. Nevertheless, until further studies are conducted that determine the clinical performance of the multiplex technology, the initial screening of patients for autoantibodies with IIF is still considered necessary.

Serial ANCA determinations for monitoring disease activity in patients with ANCA-associated vasculitis: systematic review

BACKGROUND

Antineutrophil cytoplasmic antibodies (ANCAs) are considered by some investigators to be sensitive markers of disease activity and have been suggested to predict relapse and guide therapeutic decisions. Studies using serial ANCA monitoring in patients with ANCA-associated vasculitis (AASV) have yielded controversial results during the last 15 years. To assess the diagnostic value of serial ANCA testing in the follow-up of patients with AASV, we conducted a systematic review of the available literature.

METHODS

Studies were identified by a comprehensive search of the PubMed and BIOSIS+/RRM databases, as well as hand searching. Method quality of all eligible studies was assessed with respect to external and internal validity according to established criteria for diagnostic studies.

RESULTS

Twenty-two studies met our inclusion criteria, including a total of 950 patients. Whereas generalizability was not a major problem, assessment of internal validity showed that only a minority of studies reported the combination of consecutive patient recruitment, prospective data collection, and independent determination of both index and reference tests, considered as the ideal for diagnostic test studies. Quantitative meta-analytic calculations were not conducted because of the presence of considerable method heterogeneity.

CONCLUSION

The presence of considerable methodological heterogeneity combined with methodological shortcomings with respect to internal validity in the majority of included studies preclude firm conclusions from the available literature concerning the clinical value of serial ANCA determinations for monitoring the follow-up of patients with AASV.

Prevalence and clinical significance of antineutrophil cytoplasmic antibodies in Churg-Strauss syndrome

OBJECTIVE

Churg-Strauss syndrome (CSS) is classified among the so-called antineutrophil cytoplasmic antibody-associated systemic vasculitides (AASVs) because of its clinicopathologic features that overlap with the other AASVs. However, while antineutrophil cytoplasmic antibodies (ANCAs) are consistently found in 75-95% of patients with Wegener's granulomatosis or microscopic polyangiitis, their prevalence in CSS varies widely and their clinical significance remains uncertain. We undertook this study to examine the prevalence and antigen specificity of ANCAs in a large cohort of patients with CSS. Moreover, we evaluated the relationship between ANCA positivity and clinicopathologic features.

METHODS

Immunofluorescence and enzyme-linked immunosorbent assay were used to determine the presence or absence of ANCAs in 93 consecutive patients at the time of diagnosis. The main clinical and pathologic data, obtained by retrospective analysis, were correlated with ANCA status.

RESULTS

ANCAs were present by immunofluorescence in 35 of 93 patients (37.6%). A perinuclear ANCA (pANCA) pattern was found in 26 of 35 patients (74.3%), with specificity for myeloperoxidase (MPO) in 24 patients, while a cytoplasmic ANCA pattern, with specificity for proteinase 3, was found in 3 of 35 patients (8.6%). Atypical patterns were found in 6 of 30 patients with anti-MPO antibodies (20.0%). ANCA positivity was associated with higher prevalences of renal disease (51.4% versus 12.1%; P < 0.001) and pulmonary hemorrhage (20.0% versus 0.0%; P = 0.001) and, to a lesser extent, with other organ system manifestations (purpura and mononeuritis multiplex), but with lower frequencies of lung disease (34.3% versus 60.3%; P = 0.019) and heart disease (5.7% versus 22.4%; P = 0.042).

CONCLUSION

ANCAs are present in approximately 40% of patients with CSS. A pANCA pattern with specificity for MPO is found in most ANCA-positive patients. ANCA positivity is mainly associated with glomerular and alveolar capillaritis.

Wegener's granulomatosis: The current understanding

Wegener's granulomatosis (WG) is a rare systemic disease characterized by necrotizing granulomatous inflammation of the upper and lower respiratory tract, glomerulonephritis and vasculitis. It occurs as a limited form or generalized form and usually presents with nonspecific symptoms in its early stages, making the diagnosis of this disease more elusive. Strawberry gingivitis is the most common oral manifestation and is characteristic. Prompt recognition of this early manifestation is of utmost importance for the institution of early treatment, thereby avoiding serious complications. The present paper selectively reviews the literature regarding the current status of WG with respect to diagnosis, laboratory features, and treatment.

What do antineutrophil cytoplasmic antibodies (ANCA) tell us?

Antineutrophil cytoplasmic antibodies (ANCA) are autoantibodies directed against antigens found in the cytoplasmic granules of neutrophils and monocytes. ANCA testing is usually performed to help diagnose or exclude Wegener's granulomatosis and microscopic polyangiitis. The three most commonly used assays are indirect immunofluorescence (IIF) and the direct and 'capture' enzyme-linked immunosorbent assays (ELISAs) for ANCA directed against proteinase 3 (PR3) and myeloperoxidase (MPO). Although the International Consensus Statement for Testing and Reporting ANCA recommends that all sera are screened for ANCA by IIF and that IIF-positivity is confirmed by direct ELISAs, some laboratories test by direct ELISA alone, others screen with direct ELISA and confirm positive sera by IIF, and a few use capture ELISAs. This chapter discusses the various forms of vasculitis associated with ANCA, the usefulness of each of the ANCA assays and how ANCA testing can be used in the management of patients with small-vessel vasculitis.

Use of immunofluorescence and confocal laser scanning microscopy in identifying rare cases of anti-neutrophil cytoplasmic antibodies (ANCA) showing dual specificities to myeloperoxidase and proteinase3

Anti-neutrophil cytoplasmic antibodies (ANCA) are the immunodiagnostic markers for idiopathic necrotizing crescentic glomerulonephritis affecting mainly medium to small sized blood vessels. The diagnosis of ANCA associated vasculitis (AAV) is mainly based on clinical and histopathological characteristics along with the serological evidence. Immunofluorescence microscopy (IIF) is considered as the "gold standard" for ANCA detection, and ANCA showing two major patterns ie, cytoplasmic (c-ANCA) and perinuclear (p-ANCA) react with different antigenic targets of neutrophils like Proteinase3 (PR3) and Myeloperoxidase (MPO). A third unusual and rare immunofluorescence pattern called as "X- ANCA" or atypical ANCA is also sometimes seen. The difficulty in identification of ANCA immunofluorescence patterns is mainly seen due to the rare dual patterns seen in the same sera and also the additional nuclear immunofluorescence seen due to presence of anti-nuclear antibodies. ANCA testing by immunofluorescence and Confocal Laser scanning microscopy, as well as by specific ELISAs for detection of anti-PR3 and anti-MPO antibodies have helped in improving the diagnosis. Patients having dual specificities to MPO and PR3 in a patient is a rare finding. Among 425 clinically and histopathologically proven cases of AAV, eight patients (1.9%) had dual specificities, of which five patients showed mixed immunofluorescence pattern and 3 patients showed X-ANCA pattern which was confirmed by both immunofluorescence and Confocal Laser scanning microscopy and the dual specificities to MPO and PR3 were detected by individual ELISAs.

Clinical applications of antineutrophil cytoplasmic antibody testing

PURPOSE OF REVIEW

Antineutrophil cytoplasmic antibodies are closely associated with Wegener granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome and have contributed to new pathogenetic concepts and improved nomenclature of systemic vasculitides (antineutrophil cytoplasmic antibody-associated vasculitides). However, the application of antineutrophil cytoplasmic antibody testing as a clinical diagnostic tool is still regarded as controversial. This review summarizes the most recent developments in the field, identifies areas of uncertainty, and gives practical guidelines.

RECENT FINDINGS

The problems of antineutrophil cytoplasmic antibody testing include the diversity of antineutrophil cytoplasmic antibody target antigens, assay standardization and performance, the application of antineutrophil cytoplasmic antibody testing in a clinical setting with a low pretest probability, and, finally, the widespread assumption that antineutrophil cytoplasmic antibody titers alone may closely reflect disease activity and therefore may be used to guide therapy.

SUMMARY

Recent findings demonstrate that the combined use of indirect immunofluorescence tests and solid phase assays to detect antineutrophil cytoplasmic antibody directed against myeloperoxidase and proteinase 3 can minimize the occurrence of false-positive antineutrophil cytoplasmic antibody results. Furthermore, the yield of antineutrophil cytoplasmic antibody testing can be improved by the use of a well-standardized test, adherence to published guidelines, and restricting the use of the tests to clinical situations with a rather high pretest probability for antineutrophil cytoplasmic antibody-associated vasculitides. However, treatment decisions should be based on the clinical presentation of the patient and histologic findings and not on the results of antineutrophil cytoplasmic antibody testing alone.

The binding of proteinase 3 antineutrophil cytoplasmic antibodies (PR3-ANCA) varies in different ELISAs

BACKGROUND

The demonstration of proteinase 3 specific antineutrophil cytoplasmic antibodies (PR3-ANCA), and the estimation of antibody values are useful in the diagnosis and management of patients with Wegener's granulomatosis (WG). However, external quality assessment programmes suggest that PR3-ANCA binding varies in different assays.

AIM

To demonstrate variations in PR3-ANCA binding in different commercial and in house enzyme linked immunosorbent assays (ELISAs).

METHOD

Binding of a PR3-ANCA standard and 19 sera from patients with WG was compared in eight commercial and in house assays. Binding was expressed in different units depending on the kit.

RESULTS

One commercial assay performed unsatisfactorily. Three commercial kits produced PR3-ANCA binding (70, 102, and 84 U/ml) close to the expected value for the standard (100 U/ml). Serial dilutions of this standard were linear in only one commercial assay and the in house assay. Sera from patients with WG with borderline binding in the in house assay bound in the eight commercial kits at 0-148 kit units; low binding sera ranged from 0 to 273 units; moderately strong sera bound at 7-260 units; and strongly binding sera bound at 13-336 units. In four assays, at least one strongly positive serum bound at levels greater than the provided range.

CONCLUSIONS

Levels of antibody binding and units of binding have not been standardised in commercially available PR3-ANCA ELISAs. This may affect the diagnosis and management of patients with WG, in addition to the implementation of international guidelines for treatment.

Anticorpo anticitoplasma de neutrófilos (ANCA) em pioderma gangrenoso, um marcador sorológico para associação com doenças sistêmicas: estudo de oito casos

FUNDAMENTOS: A etiopatogenia da retocolite ulcerativa inespecífica (RCUI) e de suas manifestações extra-intestinais permanece em discussão, embora o envolvimento do sistema imune seja enfatizado, e uma possível participação dos neutrófilos é demonstrada pela detecção do anticorpo anticitoplasma de neutrófilo (ANCA) nessa doença inflamatória intestinal. O pioderma gangrenoso (PG) é considerado manifestação cutânea rara da retocolite ulcerativa, e o Anca também tem sido detectado nessa dermatose. OBJETIVOS: Investigar a relação entre o comportamento clínico da RCUI e o aparecimento do PG e sua associação com ANCA. CASUÍSTICA E MÉTODOS: Anca foi pesquisado nos soros de oito pacientes com PG, quatro apresentando RCUI, e os outros, PG não associado a doenças sistêmicas. RESULTADOS: Não se detectou o Anca nos soros dos portadores exclusivamente de pioderma gangrenoso. Dois casos de pancolite em atividade inflamatória acompanhada de pioderma e colangite esclerosante primária (CEP) apresentaram positividade para ANCA, enquanto os soros de dois outros pacientes com RCUI e PG tiveram resultados negativos. CONCLUSÕES: A Presença de ANCA nos soros de pacientes com PG associado a RCUI e CEP sugere que a associação com CEP seja responsável pela positividade do ANCA na presente amostra.