Antineutrophil cytoplasmic autoantibodies in inflammatory bowel disease

Diagnostic precision of anti-Saccharomyces cerevisiae antibodies and perinuclear antineutrophil cytoplasmic antibodies in inflammatory bowel disease

AIMS

The aim of this study was to assess the diagnostic precision of antiSaccharomyces cerevisiae (ASCA) and perinuclear antineutrophil cytoplasmic antibodies (pANCA) in inflammatory bowel disease (IBD) and evaluate their discriminative ability between ulcerative colitis (UC) and Crohn's disease (CD).

METHODS

Meta-analysis of studies reporting on ASCA and pANCA in IBD was performed. Sensitivity, specificity, and likelihood ratios (LR+, LR-) were calculated for different test combinations for CD, UC, and for IBD compared with controls. Meta-regression was used to analyze the effect of age, DNAse, colonic CD, and assay type.

RESULTS

Sixty studies comprising 3,841 UC and 4,019 CD patients were included. The ASCA+ with pANCA- test offered the best sensitivity for CD (54.6%) with 92.8% specificity and an area under the ROC (receiver operating characteristic) curve (AUC) of 0.85 (LR+ = 6.5, LR- = 0.5). Sensitivity and specificity of pANCA+ tests for UC were 55.3% and 88.5%, respectively (AUC of 0.82; LR+ = 4.5, LR- = 0.5). Sensitivity and specificity were improved to 70.3% and 93.4% in a pediatric subgroup when combined with an ASCA- test. Meta-regression analysis showed decreased diagnostic precision of ASCA for isolated colonic CD (RDOR = 0.3).

CONCLUSIONS

ASCA and pANCA testing are specific but not sensitive for CD and UC. It may be particularly useful for differentiating between CD and UC in the pediatric population.

Role of auto-antibodies for the diagnosis of chronic cholestatic liver diseases

Auto-antibodies are an integral part of the diagnostic armentarium in chronic cholestatic liver disorders, such as primary sclerosing cholangitis (PSC), primary biliary cirrhosis (PBC),auto-immune cholangitis, or overlap syndromes among these disorders. However, care should be taken not to overestimate the diagnostic specificity. Auto-antibodies to mitochondrial antigens(AMAs) with reactivity to the E2 subunit of the pyruvate dehydrogenase complex represent the hallmark antibody for the diagnosis of PBC, whereas antinuclear antibodies (ANAs)with low disease specificity are found in up to 50% of these sera. Antibodies that recognize nuclear envelope proteins exert a similarly high diagnostic specificity as AMA in PBC but occur at a rather low prevalence. The role of auto-antibodies is less well-studied for patients with PSC, but there is growing evidence that only antineutrophil cytoplasmic antibodies(ANCAs) are of relevant diagnostic significance. In contrast, auto-antibodies-particularlyAMAs-do not contribute to the diagnosis of auto-immune cholangitis, whereas ANCAs,ANAs, smooth muscle antibodies, and AMAs are of varying significance in PBC-auto-immune hepatitis (AIH) or PSC-AIH overlap syndromes. It has been widely accepted that the course of the auto-antibody serum end point titers are not suited for the clinical management of patients with chronic cholestatic liver disorders. Additionally, auto-antibodies in these disorders usually do not contribute to the immunopathogenesis of the disease.

Anti-neutrophil antibodies in primary sclerosing cholangitis

Anti-neutrophil specific antibodies are detected in up to 88% of patients with PSC. The labelling pattern of neutrophils produced by these antibodies when examined by indirect immunofluorescence microscopy is distinct from that produced by anti-neutrophil cytoplasmic antibodies (ANCA) in vasculitic diseases. The antigen(s) recognized by anti-neutrophil antibodies in PSC is not yet known but appears to be localized to the periphery of the nucleus. Accordingly, the term peripheral anti-neutrophil nuclear antibodies (p-ANNA) is more appropriate than the frequently used p-ANCA. As the titre of p-ANNA in PSC does not correlate with disease-specific clinical parameters, they are not useful markers for the management of patients. However, the high prevalence of p-ANNA in PSC makes them a reasonable diagnostic marker if used in conjunction with other standard diagnostic tests. The role of anti-neutrophil antibodies in the pathogenesis of PSC, if any, remains to be established.

Rheumatologic manifestations of gastrointestinal diseases

One of the most significant extraintestinal manifestations of gastrointestinal diseases is rheumatologic disorders. The gastrointestinal diseases with rheumatologic manifestations can be divided into two major categories: intestinal disorders and disorders of the liver, biliary tree, and pancreas. The cause of diseases in each of these categories is different. Although intestinal permeability and immune responsiveness are frequently implicated in disorders of the intestine, diseases of the liver, biliary tree, and pancreas usually involve the production of autoantibodies, cytokines, or enzymes. Treatment of rheumatologic complications frequently involves therapy directed at the underlying gastrointestinal disease.

Large intestinal lymphocytic phlebitis and venulitis in chronic ulcerative colitis

Colonic vasculitis is seen in Crohn's disease and as a component of primary systemic vasculitis. It has rarely been described in chronic ulcerative colitis. Here we report a case of ulcerative colitis with prominent transmural lymphocytic phlebitis and venulitis. Although this is, to our knowledge, the first description of such an association, its recognition is important if confusion with other entities is to be avoided. The etiology of the vascular changes is unclear but they may be a secondary phenomenon induced by antigens, toxins or cytokines draining from the inflamed mucosa.

Vasculitis

Many cutaneous and systemic disorders are associated with inflammation and necrosis of blood vessels. Several classifications of vasculitis have been used. Internists tend to utilize the classification of Fauci with modifications such as those by Cupps. Gibson and Ryan, who are dermatopathologists, have classified vasculitis based on vessel size, leukocyte type, and presence of granulomas. A more recent classification has been developed by Jennette, a pathologist, and colleagues. The etiology of vasculitis is varied; it includes bacteria, viruses, chemicals, autoimmune disease, malignancy and abnormal exogenous and endogenous proteins. Leukocytoclastic vasculitis can be experimentally reproduced by the Arthus phenomenon. IgM and C3 are found in cutaneous blood vessels and associated with circulating immune complexes. CH50, C3 and C4 may be reduced in serum. Increased incidence of nasal carriage of staphylococci is associated with higher relapse rates in Wegener's granulomatosis and toxic shock syndrome toxin from staphylococci is associated with the Kawasaki syndrome. Additionally, at least four systemic vasculitic drug reactions can be confirmed with patch testing. Antineutrophil cytoplasmic antibodies (ANCA) are found in association with certain systemic vasculitides. These may be tested with indirect immunofluorescence and enzyme linked immunosorbent assays (ELISA) with radioimmunoassays. Originally cytoplasmic ANCA (cANCA) was identified with proteinase 3 as the antigen and perinuclear ANCA (pANCA) was related to myeloperoxidase. While cANCA is very specific for proteinase 3, pANCA is associated with a number of antigens other than myeloperoxidase. pANCA is found with alcohol fixed but not formalin-fixed neutrophils. cANCA is particularly sensitive and specific for Wegener's granulomatosis and predicts prognosis and response to therapy. pANCA is not so specific and is associated with a number of other vasculitic syndromes. Cutaneous vasculitis is managed primarily with colchicine, dapsone and prednisone, with recent studies indicating that there may be a synergistic effect of pentoxifylline with dapsone. Systemic vasculitis involves treatment with various agents. Recently it has been observed that co-trimoxazole (trimethoprim/sulfamethoxazole) is useful in many cases of Wegener's granulomatosis along with other more toxic chemotherapeutic agents.

Molecularly defined HLA-DR2 alleles in ulcerative colitis and an antineutrophil cytoplasmic antibody-positive subgroup

BACKGROUND/AIMS

Although HLA-DR2 is associated with Japanese ulcerative colitis, data regarding an HLA-DR2 association in other populations are conflicting. A recent study suggests that HLA-DR2 is only associated with antineutrophil cytoplasmic antibody-positive ulcerative colitis. The aim of this study was to determine whether HLA-DR2 or the molecularly defined alleles within the HLA-DR2 group are associated with ulcerative colitis or a perinuclear antineutrophil cytoplasmic antibody-positive subgroup.

METHODS

Unrelated white patients with a history of ulcerative colitis (n = 97) and control subjects matched to patients for Jewish ethnicity and sex (n = 149) were studied. An immunofluorescence assay was used to detect perinuclear antineutrophil cytoplasmic antibodies. A molecular, DNA-based method was used to perform HLA-DR2 typing.

RESULTS

HLA-DRB1*1601 was present in 11 of 149 controls and 1 of 97 patients (P = 0.031, corrected P, not significant; Fisher's Exact Test). There were no other significant differences between ulcerative colitis or ulcerative colitis stratified by perinuclear antineutrophil cytoplasmic antibody status and controls.

CONCLUSIONS

The HLA-DR2 group of alleles is not associated with ulcerative colitis or a perinuclear antineutrophil cytoplasmic antibody-positive subgroup. The unexpected finding of a decreased frequency of HLA-DRB1*1601 in ulcerative colitis should be further investigated.

Wegener's granulomatosis and antineutrophil cytoplasmic autoantibodies

Serologic tests for antineutrophil cytoplasmic autoantibodies can serve as markers for a number of necrotizing vasculitides and other inflammatory disorders. In the case of Wegener's granulomatosis, an immunofluorescent cytoplasmic pattern and immunoassay for proteinase 3 are quite specific for the disease and are capable of serving as additional criteria for diagnosis. As with any laboratory test, however, results are to be interpreted in the whole clinical and pathologic framework of the disease.