Pulmonary capillaritis: a rare extra-intestinal manifestation of inflammatory bowel disease

Novel clinical and diagnostic aspects of antineutrophil cytoplasmic antibodies

Antineutrophil cytoplasmic antibodies (ANCA) are the serological hallmark of some idiopathic systemic vasculitides. Besides the investigation of ANCA-associated vasculitis (AAV) and constant effort for a standardized nomenclature and classification of the AAV, a main focus of research during the last few years has been to constantly improve the performance of enzyme immunoassays. With the latest so called third generation ELISA, this goal seemed to be fulfilled. The International Consensus Statement on Testing and Reporting of ANCA gave recommendations for standardized strategies for the serological diagnosis of ANCA. New developments now target the system immanent drawbacks of the respective diagnostic methods, be it the need for batching and the long time to result for ELISA, or the high likelihood of error and subjectivity of indirect immunofluorescence (IIF). Random access technology and multiplexing for solid phase assays as well as digital imaging for IIF are tools which may help to expedite and simplify routine diagnostics in the lab and in emergency settings. Recent findings indicate that PR3-ANCA have clinical utility beyond the diagnosis of AAV. PR3-ANCA can also serve as an aid for the differentiation between ulcerative colitis (UC) and Crohn's disease (CrD) and the stratification of UC patients. This review provides a detailed review of what is known about ANCA and highlights the latest research and state-of-the-art developments in this area.

Presence of anti-proteinase 3 antineutrophil cytoplasmic antibodies (anti-PR3 ANCA) as serologic markers in inflammatory bowel disease

Anti-proteinase 3 anti-neutrophil cytoplasmic antibodies (anti-PR3 ANCA) represent an established serologic marker of active granulomatosis with polyangiitis, but their role as a serologic marker in inflammatory bowel disease (IBD) remains uncertain. This study evaluates the presence of anti-PR3 ANCA and their validity as a serologic marker to aid in the diagnosis of IBD. Retrospectively, 142 serum samples obtained at early stages of the disease were analyzed with a new chemiluminiscent assay for the measurement of anti-PR3 ANCA. The results were correlated to the diagnosis, clinical, and therapeutic data, and ANCA and anti-Saccharomyces cerevisiae antibody (ASCA) measurements available from routine clinical practice. Anti-PR3 ANCA were significantly more prevalent (p < 0.0001) and their titers significantly higher (p < 0.0001) among ulcerative colitis compared with Crohn's disease patients. Receiver operating characteristic curve analysis performed with anti-PR3 ANCA titers to assess the diagnostic accuracy of the assay gave an area under the curve of 0.81 (95 % CI (0.76-0.89); p < 0.0001), with a cut-off titer of 11.8 chemiluminescent units displaying 52.1 % sensitivity and 97.3 % specificity for ulcerative colitis. Combining anti-PR3 ANCA positivity with IgA ASCA negativity as the diagnostic parameter demonstrated highest diagnostic utility, with a sensitivity and specificity of 47.5 % and 98.2 %, respectively. In our cohort, anti-PR3 ANCA was significantly more prevalent in ulcerative colitis than in Crohn's disease patients, which suggests a possible role of anti-PR3 ANCA as a serologic marker to aid in the diagnosis of IBD.

PR3-ANCA: a promising biomarker for ulcerative colitis with extensive disease

BACKGROUND

We determined if PR3-ANCA is a biomarker that differentiates ulcerative colitis (UC) from Crohn's disease (CrD).

METHODS

A total of 946 sera were tested, including 86 granulomatosis with polyangiitis (GPA) and 491 inflammatory bowel disease (IBD) patients (283 UC and 208 CrD), 264 pathological controls (various diseases) and 105 healthy individuals. All samples were tested for PR3-ANCA by ELISA (QUANTA Flash Lite®, INOVA Diagnostics) and chemiluminescent immunoassays (CIA QUANTA Flash PR3). Conventional anti-neutrophil cytoplasmic antibody (ANCA) indirect immunofluorescence assays (IIF) was performed with NOVA Lite™ (INOVA Diagnostics).

RESULTS

PR3-ANCA by CIA were detected in 31.1% UC vs. 1.9% CrD sera (p=2.2E-16), and by ELISA in 6% UC and 0% CrD (p=0.0003). In GPA patients, PR3-ANCA were detected in 75.6% by CIA and 61.6% by ELISA (p<0.05). PR3-ANCA by CIA were more prevalent in E3-UC compared to E1/2-UC (p<0.05), and in patients with shorter disease duration (p<0.0001). PR3-ANCA showed similar sensitivity, but significantly higher specificity (p<0.05), compared to atypical pANCA by IIF.

CONCLUSION

The novel PR3 CIA may prove helpful in the differentiation of CrD from UC, as well as in the identification of UC patients with more extensive disease.