RESUMO
Anti-neutrophil cytoplasmic antibodies (ANCA) directed to proteinase 3 (PR3) represent highly established markers for patients with ANCA-associated vasculitis (AAV). PR3-ANCA have also demonstrated utility in the management of inflammatory bowel disease (IBD). More specifically, PR3-ANCA discriminate individuals with ulcerative colitis (UC) from Crohn's disease (CD) patients and are associated with disease severity, activity, and treatment non-response. Here, we aim to summarize the current data on the diagnostic utility of PR3-ANCA in IBD. A structured, systematic literature review, including three electronic databases, was conducted on June 6th, 2023, to identify studies assessing the diagnostic accuracy of the QUANTA Flash® PR3 assay in UC vs. CD patients. Electronic searches were supplemented by hand searching. A hierarchical, bivariate, mixed-effect meta-analysis was conducted using the metandi function, as per the Cochrane collaboration recommendations. Study quality was assessed using the QUADAS-2 tool, which considers the risk of bias and applicability. Six out of a hundred and eleven citations met the inclusion criteria and reported QUANTA Flash® PR3 diagnostic accuracy in UC vs. CD (UC, n = 667, CD, n = 682 patients). The sensitivity/specificity point estimate for UC was 34.9%/95.9%. This resulted in a Diagnostic Odds Ratio (DOR) of 12.6. The risk of bias was low in the index test and reference standard domains. Four of the six studies (67%) showed an unclear risk of bias in patient selection and in flow and timing domains. All studies had low concerns about applicability in all the domains. PR3-ANCA measured with the QUANTA Flash® PR3 assay represent novel diagnostic markers in IBD and enables discrimination between UC and CD.
RESUMO
BACKGROUND: The importance of circulating antibodies as biomarkers of kidney disease has recently been recognized. However, no study has systematically described the methodology of sample preparation and storage regarding antibodies as biomarkers of kidney disease. It remains unknown whether repetitive freeze-thaw cycles, physical disturbances, storage at different temperatures or for different periods of time, or haemolytic or turbid serum samples affect antibody measurements. The aim of this study was to investigate the stabilities of antibodies associated with kidney disease in serum samples under various relevant clinical and research conditions. METHODS: We stored serum samples in the following different conditions: repetitive freeze-thaw cycles (1, 6 or 12 times), long-term storage (7 or 12 months at -80 °C), physical disturbance (1 or 8 h), and storage at 4 °C (1, 3 or 6 weeks) and room temperature (1 or 7 days). The stabilities of the anti-phospholipase A2 receptor (anti-PLA2R), anti-glomerular basement membrane, anti-myeloperoxidase and anti-proteinase 3 antibodies were evaluated with enzyme-linked immunosorbent assays (ELISA). RESULTS: We found that repetitive freeze-thaw cycles did not have a significant effect on the stabilities of the abovementioned antibodies in clear serum samples. The ELISA readings of haemolytic and turbid serum samples tended to increase and decrease, respectively. Neither long-term storage at -80 °C nor physical disturbance had a significant effect on anti-PLA2R antibody stability in sealed serum samples. The concentrations of most of these antibodies increased in unsealed serum samples that were stored at 4 °C for more than 6 weeks or at room temperature for more than 7 days. DISCUSSION: Our findings revealed that the abovementioned circulating antibodies that are used as biomarkers for kidney disease had stable physicochemical properties, structures and immunoreactivities such that they were not influenced by repetitive freeze-thaw cycles, physical disturbances or long-term storage at -80 °C. However, the ELISA readings tended to change for haemolytic, turbid and unsealed serum samples.
RESUMO
We report here the case of a 50-years-old man treated for mixed connective tissue disease (MCTD) positive for anti-U1 ribonucleoprotein (U1RNP) antibodies who secondarily developed a granulomatosis with polyangiitis (GPA) associated with anti-proteinase 3 anti-neutrophil cytoplasmic antibodies (PR3-ANCA). We then evaluated the frequency of the association between anti-U1RNP and anti-PR3-ANCA antibodies by a systematic retrospective study in ten European hospitals. Overall, out of 11,921 samples analyzed for both auto-antibodies, 18 cases of anti-U1RNP and anti-PR3-ANCA double positivity were found and only one patient presented with both MCTD and GPA symptoms. Our retrospective analysis indicates that anti-U1RNP and anti-PR3-ANCA antibodies double positivity is infrequent and very rarely associated with both MTCD and GPA. Our observation describes for the first time the coexistence of MTCD and severe GPA in a Caucasian patient. Association of anti-U1RNP and ANCA antibodies was rarely reported in the literature. Eleven cases of MCTD and ANCA vasculitis have been reported to date, with only two cases with anti-PR3-ANCA association, and only one vasculitis. The seven other cases reported in the literature presented with an association of MCTD and microscopic polyangiitis which appears to be a more frequent presentation than MTCD associated with GPA.