Clinical spectrum associated with positive ANCA titres in 94 consecutive patients: is there a relation with PR-3 negative c-ANCA and hypergammaglobulinaemia?

Diagnostic accuracy of antineutrophil cytoplasmic antibodies (ANCA) in predicting relapses of ANCA-associated vasculitis: systematic review and meta-analysis

Relapse in antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) is associated with significant morbidity and mortality. Utility of ANCA for prediction of relapses is still controversial. PubMed/MEDLINE, Scopus, and WebOfScience were searched, screened and confirmed for inclusion [PROSPERO No: CRD42020220308]. Studies measuring serial ANCA by ELISA or indirect immunofluorescence (IF), reporting relapses with sufficient data to calculate sensitivity and specificity were included. Diagnostic odds ratio (OR), sensitivity, specificity and likelihood ratios (LR) were synthesized using a bivariate mixed-effect regression model. Sub-group analysis included a comparison between ELISA and IIF, anti-myeloperoxidase (MPO) and -proteinase 3(PR3), and type of rise in ANCA. For meta-analysis of survival outcomes, hazard ratios were synthesized using a random-effect model. QUADAS-2 was used for assessing quality of studies, I² statistic for heterogeneity Begg's test for publication bias. 2946 abstracts and 43 full-texts were reviewed to identify 26 eligible studies that included 2623 patients with AAV and 848 relapses. Overall heterogeneity was high [I² = 99%] and the overall risk of bias was low to moderate. ANCA positivity by either ELISA or immunofluorescence for predicting relapse of AAV had a sensitivity of 0.70(95% CI 0.58-0.81), specificity of 0.66(0.55-0.76), positive LR of 2.1(1.6-42.7) and negative LR of 0.44(0.30-0.60). ELISA performed marginally better [OR: 5(3-7)] than IIF [OR: 4(2-9)] with similar sensitivity, specificity, PLR and NLR. The area under the curve for PR3 was 0.74(0.7-0.77), while that for MPO was not computed as the number of eligible studies was only three. In the survival analysis, the hazard ratio for relapse was 3.11(1.7-5.65). The meta-analysis shows modest accuracy of ANCA in predicting relapses of ANCA vasculitis and supports the use of serial ANCA monitoring as a biomarker for relapse.

Abnormal antibodies: what do you do?

Systemic autoimmune rheumatic diseases encompass a vast array of autoantibodies which are very useful to confirm a suspected diagnosis. This article gives an overview of the most common autoantibodies, how they are tested and the significance of a positive test in a clinical context.

Mononeuritis multiplex as a presenting feature of Wegener granulomatosis: a case report

We report the case of a man presenting with clinical features of a mononeuritis multiplex, a perinuclear-ANCA (p-ANCA), and a renal biopsy suggestive of Wegener granulomatosis (WG). We wish to highlight this case as a learning point for clinicians as WG rarely presents in this form, and can be easily overlooked as a cause of mononeuritis multiplex.

Positive C-ANCA and cavitary lung lesion: recurrence of Wegener granulomatosis or aspergillosis?

A case of a cavitary lung lesion in the right middle lobe of a 34-year-old woman who presented with hemoptysis is presented. The patient had a 2-year history of Wegener granulomatosis that had been treated with cyclophosphamide and corticosteroids. Although the patient gradually achieved remission of her disease, she developed new pulmonary symptoms and a cavitary lesion in her right lung. Further workup revealed elevated C- and P-ANCA titers. Following partial resection of her right lung, she was found to have an aspergilloma and no evidence of active Wegener granulomatosis. Pulmonary aspergillosis was felt to be the cause of both the hemoptysis and the cavitary lesion. We postulate that C-ANCA and P-ANCA were falsely positive in this case. Although rare, false positive C-ANCA and P-ANCA have been reported in pulmonary fungal infections.

Immunoglobulin isotypes of anti-myeloperoxidase and anti-lactoferrin antibodies in patients with collagen diseases

To investigate the prevalence and clinical relevance of immunoglobulin (Ig) isotypes of antimyeloperoxidase (MPO) and antilactoferrin (LF) antibodies in collagen diseases, enzyme-linked immunosorbent assay was employed to detect the Ig isotypes of both antibodies. The purified proteins of MPO and LF were used as two major representative antigens for anti-neutrophil cytoplasmic antibodies (ANCA) with a perinuclear staining pattern by an indirect immunofluorescent technique. We examined 131 serum samples from 79 patients with rheumatoid arthritis (RA), 32 with systemic lupus erythematosus (SLE), 14 with progressive systemic sclerosis (PSS), 6 with polymyositis/dermatomyositis (PM/DM), and 5 with idiopathic crescentic glomerulonephritis who served as positive controls and 36 healthy subjects who served as controls. A limited number of patients with RA (4-10%), SLE (6-9%), and PSS (7-14%) but not PM/DM showed positive IgG or IgA anti-MPO antibody (MPO-ANCA) but not IgM MPO-ANCA. However, 10-20% of RA, 40-60% of SLE, 20-36% of PSS but none of the PM/DM patients showed positive IgG, IgA, or IgM anti-LF antibody (LF-ANCA). MPO- and LF-ANCA positivity in RA patients was correlated with markers of disease activity such as the erythrocyte sedimentation rate, C-reactive protein, and serum Ig levels. IgG LF-ANCA but not MPO-ANCA positivity in SLE patients also was correlated with the disease activity index but not with clinical features. Neither MPO- nor LF-ANCA positivity in PSS patients was correlated with any clinical features. Overall, both MPO- and LF-ANCA were found mainly in RA, SLE, and PSS patients but not in PM/DM patients. The Ig isotypes of MPO- and LF-ANCA frequently belonged to both IgG and IgA and rarely to the IgM class. Both MPO- and LF-ANCA positivity reflected disease activity in RA and SLE rather than specific organ involvement.

Antineutrophil cytoplasmic antibodies and associated diseases: a review of the clinical and laboratory features

There have been a number of recent advances in this field. First, the "International Consensus Statement on Testing and Reporting of Antineutrophil Cytoplasmic Antibodies (ANCA)" has been developed to optimize ANCA testing. It requires that all sera are tested by indirect immunofluorescent (IIF) examination of normal peripheral blood neutrophils and, where there is positive fluorescence, in enzyme-linked immunosorbent assays (ELISAs) for antibodies against both proteinase 3 (PR3) and myeloperoxidase (MPO). Testing will be further improved when international standards and common ELISA units are available. Second, new diagnostic criteria for the small vessel vasculitides that take into account ANCA-positivity and target antigen specificity as well as histologic features are currently being produced. Third, we understand that the complications associated with treatment of the ANCA-associated vasculitides are often more hazardous than the underlying disease, and regimens that use effective but less toxic agents are being evaluated. The factors associated with increased risk of relapse, however, remain incompletely understood. Finally, ANCA with specificities other than PR3 and MPO are present in many nonvasculitic autoimmune diseases. Their clinical significance is still largely unclear, and some of the target antigens are present in other cells as well as neutrophils and thus are not strictly "ANCA."

Sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease that progresses to death as a result of liver failure or cholangiocarcinoma. Susceptibility to PSC is associated with the HLA A1-B8-DR3 haplotype, and new associations with HLA C and tumor necrosis factor genes have been detected. A circulating antineutrophil cytoplasmic antibody is found in many patients with PSC, but its antigen or antigens have not been identified. Some studies suggest that this antigen may be an anti-nuclear membrane protein rather than cytoplasmic. Diagnosis of PSC is based on endoscopic retrograde cholangiography, but magnetic resonance cholangiography is a promising noninvasive alternative. Medical treatment remains elusive. In highly selected patients, endoscopic or even surgical treatment can be tried. Orthotopic liver transplantation remains the only effective therapy, but inflammatory bowel disease may run a more aggressive clinical course after this procedure. Sclerosing cholangitis may recur after transplantation, but this has had no clinical implications to date.