Clinical and humoral response after SARS-CoV-2 breakthrough infection in patients receiving immunosuppressant therapy.

BACKGROUND: Despite impaired humoral response in patients treated with immunosuppressants (ISPs), recent studies found similar severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) breakthrough infection compared to controls. One potential explanation is the rapid generation of humoral response on infection, but evidence is lacking. OBJECTIVES: We investigated the longitudinal dynamics of the SARS-CoV-2 antibody repertoire after SARS-CoV-2 delta and omicron breakthrough infection in patients with immune-mediated inflammatory diseases (IMIDs) receiving ISP therapy and controls. METHODS: As a prospective substudy of the national Target-to-B! (T2B!) consortium, we included IMID patients receiving ISPs therapy and controls who reported SARS-CoV-2 breakthrough infection between July 1, 2021, and April 1, 2022. To get an impression of the dynamics of the antibody repertoire, 3 antibody titers of wild-type RBD, wild-type S, and omicron RBD were measured at 4 time points after SARS-CoV-2 breakthrough infection. RESULTS: We included 302 IMID patients receiving ISPs and 178 controls. Antibody titers increased up to 28 days after breakthrough infection in both groups. However, in IMID patients receiving therapy with anti-CD20 and sphingosine-1 phosphate receptor modulators, antibody titers were considerably lower compared to controls. In the anti-TNF group, we observed slightly lower antibody titers in the early stages and a faster decline of antibodies after infection compared to controls. Breakthrough infections were mostly mild, and hospitalization was required in less than 1% of cases. CONCLUSIONS: Most ISPs do not influence the dynamics of the SARS-CoV-2 antibody repertoire and exhibit a rapid recall response with cross-reactive antibody clones toward new virus variants. However, in patients treated with anti-CD20 therapy or sphingosine-1 phosphate receptor modulators, the dynamics were greatly impaired, and to a lesser extent in those who received anti-TNF. Nevertheless, only a few severe breakthrough cases were reported.

Assessment of longitudinal serum neutrophil extracellular trap-inducing activity in anti-neutrophil cytoplasmic antibody-associated vasculitis and glomerulonephritis in a prospective cohort using a novel bio-impedance technique.

Neutrophil extracellular traps (NET) have been implicated in the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Here, we developed a novel, label-free, high-throughput bio-impedance technique to effectively measure serum NET-inducing activity. Using this technique, NET-inducing activity of serum derived from patients with AAV was assessed in a prospective cohort of 62 patients presenting with active AAV with major organ involvement. Thirty-five patients presented with new and 27 patients presented with relapsing AAV, of whom 38 had kidney and/or 31 had lung involvement. NET-inducing activity was assessed at diagnosis of active AAV (time zero), during the first 6 weeks of treatment, and after 6 months of treatment. Forty-seven patients revealed elevated NET-inducing activity at time zero. After initiation of immunosuppressive treatment, NET-inducing activity was reduced at six weeks. A subsequent increase at six months could potentially identify patients with relapsing disease (hazard ratio, 11.45 [interquartile range 1.36-96.74]). NET-inducing activity at time zero correlated with kidney function and proteinuria. Importantly, in kidney tissue, NETs co-localized with lesions typical of ANCA-associated glomerulonephritis and even correlated with systemic serum NET-inducing activity. Thus, our prospective data corroborate the importance of NET formation in AAV and ANCA-associated glomerulonephritis and the potential of longitudinal evaluation, as monitored by our novel bio-impedance assay and detailed histological evaluation.

Disease activity in patients with immune-mediated inflammatory diseases after SARS-CoV-2 vaccinations.

For patients with immune-mediated inflammatory diseases (IMIDs), concerns exist about increased disease activity after vaccination. We aimed to assess changes in disease activity after SARS-CoV-2 vaccination in patients with IMIDs, and determine risk factors for increased disease activity. In this substudy of a prospective observational cohort study (Target-to-B!), we included patients with IMIDs who received a SARS-CoV-2 vaccine. Patients reported changes in disease activity on a five-point Likert scale every 60 days for up to twelve months after first vaccination. In case of self-reported increased activity, hospital records were screened whether the treating physician reported increased activity, and for potential intensification of immunosuppressive (ISP) treatment. Mixed models were used to study determinants for self-reported increased disease activity. In total, 2111 patients were included for analysis after primary immunization (mean age 49.7 years [SD 13.7], 1329/2111 (63.0%) female), from which 1266 patients for analysis after first additional vaccination. Increased disease activity at 60 days after start of primary immunization was reported by 223/2111 (10.6%). In 96/223 (43.0%) the increase was confirmed by the treating physician and in 36/223 (16.1%) ISP treatment was intensified. Increased disease activity at seven to 60 days after additional vaccination, was reported by 139/1266 (11.0%). Vaccinations were not temporally associated with self-reported increased disease activity. Conversely, increased disease activity before first vaccination, neuromuscular disease, and multiple sclerosis were associated. Altogether, self-reported increased disease activity after vaccination against SARS-CoV-2 was recorded in a minority of patients and was generally mild. Moreover, multivariate analyses suggest that disease related factors, but not vaccinations are the major determinants for self-reported increased disease activity.

Management of adult-onset Still's disease: evidence- and consensus-based recommendations by experts.

BACKGROUND: Adult-onset Still's disease (AOSD) is a rare condition characterized by fevers, rash, and arthralgia/arthritis. Most doctors treating AOSD in the Netherlands treat <5 patients per year. Currently, there is no internationally accepted treatment guideline for AOSD. OBJECTIVES: To conduct a Delphi panel aimed at reaching consensus about diagnostic and treatment strategies for patients with AOSD and to use the outcomes as a basis for a treatment algorithm. METHODS: The Delphi panel brought together 18 AOSD experts: rheumatologists, internists and paediatricians. The Delphi process consisted of 3 rounds. In the first two rounds, online list of questions and statements were completed. In the third round, final statements were discussed during a virtual meeting and a final vote took place. Consensus threshold was set at 80%. Two targeted literature searches were performed identifying the level of evidence of the consensus-based statements. RESULTS: Consensus was reached on 29 statements, including statements related to diagnosis and diagnostic tests, definition of response and remission, the therapy, the use of methotrexate, and tapering of treatment. The panel consented on reduction of the use of glucocorticoids to avoid side-effect, and preferred the use of biologics over conventional treatment. The role of interleukin-1 and interleukin-6 blocking agents was considered important in the treatment of AOSD. CONCLUSIONS: In this Delphi panel, a high level of consensus was achieved on recommendations for diagnosis and therapy of AOSD that can serve as a basis for a treatment guideline.

Primary SARS-CoV-2 infection in patients with immune-mediated inflammatory diseases: long-term humoral immune responses and effects on disease activity.

BACKGROUND: Patients with immune-mediated inflammatory diseases (IMIDs) on immunosuppressants (ISPs) may have impaired long-term humoral immune responses and increased disease activity after SARS-CoV-2 infection. We aimed to investigate long-term humoral immune responses against SARS-CoV-2 and increased disease activity after a primary SARS-CoV-2 infection in unvaccinated IMID patients on ISPs. METHODS: IMID patients on active treatment with ISPs and controls (i.e. IMID patients not on ISP and healthy controls) with a confirmed SARS-CoV-2 infection before first vaccination were included from an ongoing prospective cohort study (T2B! study). Clinical data on infections and increased disease activity were registered using electronic surveys and health records. A serum sample was collected before first vaccination to measure SARS-CoV-2 anti-receptor-binding domain (RBD) antibodies. RESULTS: In total, 193 IMID patients on ISP and 113 controls were included. Serum samples from 185 participants were available, with a median time of 173 days between infection and sample collection. The rate of seropositive IMID patients on ISPs was 78% compared to 100% in controls (p < 0.001). Seropositivity rates were lowest in patients on anti-CD20 (40.0%) and anti-tumor necrosis factor (TNF) agents (60.5%), as compared to other ISPs (p < 0.001 and p < 0.001, respectively). Increased disease activity after infection was reported by 68 of 260 patients (26.2%; 95% CI 21.2-31.8%), leading to ISP intensification in 6 out of these 68 patients (8.8%). CONCLUSION: IMID patients using ISPs showed reduced long-term humoral immune responses after primary SARS-CoV-2 infection, which was mainly attributed to treatment with anti-CD20 and anti-TNF agents. Increased disease activity after SARS-CoV-2 infection was reported commonly, but was mostly mild. TRIAL REGISTRATION: NL74974.018.20, Trial ID: NL8900. Registered on 9 September 2020.

Adult-onset autoinflammation caused by somatic mutations in UBA1: A Dutch case series of patients with VEXAS.

BACKGROUND: A novel autoinflammatory syndrome was recently described in male patients who harbored somatic mutations in the X-chromosomal UBA1 gene. These patients were characterized by adult-onset, treatment-refractory inflammation with fever, cytopenia, dysplastic bone marrow, vacuoles in myeloid and erythroid progenitor cells, cutaneous and pulmonary inflammation, chondritis, and vasculitis, which is abbreviated as VEXAS. OBJECTIVE: This study aimed to (retrospectively) diagnose VEXAS in patients who had previously been registered as having unclassified autoinflammation. We furthermore aimed to describe clinical experiences with this multifaceted, complex disease. METHODS: A systematic reanalysis of whole-exome sequencing data from a cohort of undiagnosed patients with autoinflammation from academic hospitals in The Netherlands was performed. When no sequencing data were available, targeted Sanger sequencing was applied in cases with high clinical suspicion of VEXAS. RESULTS: A total of 12 male patients who carried mutations in UBA1 were identified. These patients presented with adult-onset (mean age 67 years, range 47-79 years) autoinflammation with systemic symptoms, elevated inflammatory parameters, and multiorgan involvement, most typically involving the skin and bone marrow. Novel features of VEXAS included interstitial nephritis, cardiac involvement, stroke, and intestinal perforation related to treatment with tocilizumab. Although many types of treatment were initiated, most patients became treatment-refractory, with a high mortality rate of 50%. CONCLUSION: VEXAS should be considered in the differential diagnosis of males with adult-onset autoinflammation characterized by systemic symptoms and multiorgan involvement. Early diagnosis can prevent unnecessary diagnostic procedures and provide better prognostic information and more suitable treatment options, including stem cell transplantation.

Immunogenicity of the mRNA-1273 COVID-19 vaccine in adult patients with inborn errors of immunity.

BACKGROUND: Patients with inborn errors of immunity (IEI) are at increased risk of severe coronavirus disease-2019 (COVID-19). Effective vaccination against COVID-19 is therefore of great importance in this group, but little is known about the immunogenicity of COVID-19 vaccines in these patients. OBJECTIVES: We sought to study humoral and cellular immune responses after mRNA-1273 COVID-19 vaccination in adult patients with IEI. METHODS: In a prospective, controlled, multicenter study, 505 patients with IEI (common variable immunodeficiency [CVID], isolated or undefined antibody deficiencies, X-linked agammaglobulinemia, combined B- and T-cell immunodeficiency, phagocyte defects) and 192 controls were included. All participants received 2 doses of the mRNA-1273 COVID-19 vaccine. Levels of severe acute respiratory syndrome coronavirus-2-specific binding antibodies, neutralizing antibodies, and T-cell responses were assessed at baseline, 28 days after first vaccination, and 28 days after second vaccination. RESULTS: Seroconversion rates in patients with clinically mild antibody deficiencies and phagocyte defects were similar to those in healthy controls, but seroconversion rates in patients with more severe IEI, such as CVID and combined B- and T-cell immunodeficiency, were lower. Binding antibody titers correlated well to the presence of neutralizing antibodies. T-cell responses were comparable to those in controls in all IEI cohorts, with the exception of patients with CVID. The presence of noninfectious complications and the use of immunosuppressive drugs in patients with CVID were negatively correlated with the antibody response. CONCLUSIONS: COVID-19 vaccination with mRNA-1273 was immunogenic in mild antibody deficiencies and phagocyte defects and in most patients with combined B- and T-cell immunodeficiency and CVID. Lowest response was detected in patients with X-linked agammaglobulinemia and in patients with CVID with noninfectious complications. The assessment of longevity of immune responses in these vulnerable patient groups will guide decision making for additional vaccinations.

Risk factors associated with short-term adverse events after SARS-CoV-2 vaccination in patients with immune-mediated inflammatory diseases.

BACKGROUND: Studies have suggested incremental short-term adverse events (AE) after repeated vaccination. In this report, we assessed occurrence and risk factors for short-term AEs following repeated SARS-CoV-2 vaccination in patients with various immune-mediated inflammatory diseases (IMIDs). METHODS: Self-reported daily questionnaires on AEs during the first 7 days after vaccination were obtained of 2259 individuals (2081 patients and 178 controls) participating in an ongoing prospective multicenter cohort study on SARS-CoV-2 vaccination in patients with various IMIDs in the Netherlands (T2B-COVID). Relative risks were calculated for potential risk factors associated with clinically relevant AE (rAE), defined as AE lasting longer than 2 days or impacting daily life. RESULTS: In total, 5454 vaccinations were recorded (1737 first, 1992 second and 1478 third vaccinations). Multiple sclerosis, Crohn's disease and rheumatoid arthritis were the largest disease groups. rAEs were reported by 57.3% (95% CI 54.8-59.8) of patients after the first vaccination, 61.5% (95% CI 59.2-63.7) after the second vaccination and 58% (95% CI 55.3-60.6) after the third vaccination. At day 7 after the first, second and third vaccination, respectively, 7.6% (95% CI 6.3-9.1), 7.4% (95% CI 6.2-8.7) and 6.8% (95% CI 5.4-8.3) of patients still reported AEs impacting daily life. Hospital admissions and allergic reactions were uncommon (<0.7%). Female sex (aRR 1.43, 95% CI 1.32-1.56), age below 50 (aRR 1.14, 95% CI 1.06-1.23), a preceding SARS-CoV-2 infection (aRR 1.14, 95% CI 1.01-1.29) and having an IMID (aRR 1.16, 95% CI 1.01-1.34) were associated with increased risk of rAEs following a vaccination. Compared to the second vaccination, the first vaccination was associated with a lower risk of rAEs (aRR 0.92, 95% CI 0.84-0.99) while a third vaccination was not associated with increased risk on rAEs (aRR 0.93, 95% CI 0.84-1.02). BNT162b2 vaccines were associated with lower risk on rAEs compared to CX-024414 (aRR 0.86, 95% CI 0.80-0.93). CONCLUSIONS: A third SARS-CoV-2 vaccination was not associated with increased risk of rAEs in IMID patients compared to the second vaccination. Patients with an IMID have a modestly increased risk of rAEs after vaccination when compared to controls. Most AEs are resolved within 7 days; hospital admissions and allergic reactions were uncommon. TRIAL REGISTRATION: NL74974.018.20 , Trial ID: NL8900. Registered on 9 September 2020.

Breakthrough infections with the SARS-CoV-2 omicron (B.1.1.529) variant in patients with immune-mediated inflammatory diseases.

OBJECTIVES: To compare the cumulative incidence and disease severity of reported SARS-CoV-2 omicron breakthrough infections between patients with immune-mediated inflammatory diseases (IMID) on immunosuppressants and controls, and to investigate determinants for breakthrough infections. METHODS: Data were used from an ongoing national prospective multicentre cohort study on SARS-CoV-2 vaccination responses in patients with IMID in the Netherlands (Target-to-B! (T2B!) study). Patients wih IMID on immunosuppressants and controls (patients with IMID not on immunosuppressants and healthy controls) who completed primary immunisation were included. The observation period was between 1 January 2022 and 1 April 2022, during which the SARS-CoV-2 omicron (BA.1 and BA.2 subvariant) was dominant. A SARS-CoV-2 breakthrough infection was defined as a reported positive PCR and/or antigen test at least 14 days after primary immunisation. A multivariate logistic regression model was used to investigate determinants. RESULTS: 1593 patients with IMID on immunosuppressants and 579 controls were included. The cumulative incidence of breakthrough infections was 472/1593 (29.6%; 95% CI 27% to 32%) in patients with IMID on immunosuppressants and 181/579 (31.3%; 95% CI 28% to 35%) in controls (p=0.42). Three (0.5%) participants had severe disease. Seroconversion after primary immunisation (relative risk, RR 0.71; 95% CI 0.52 to 0.96), additional vaccinations (RR 0.61; 95% CI 0.49 to 0.76) and a prior SARS-CoV-2 infection (RR 0.60; 95% CI 0.48 to 0.75) were associated with decreased risk of breakthrough infection. CONCLUSIONS: The cumulative incidence of reported SARS-CoV-2 omicron breakthrough infections was high, but similar between patients with IMID on immunosuppressants and controls, and disease severity was mostly mild. Additional vaccinations and prior SARS-CoV-2 infections may reduce the incidence of breakthrough infections.

CD163 and CD206 expression define distinct macrophage subsets involved in active ANCA-associated glomerulonephritis.

INTRODUCTION: Macrophages are key players in the immunopathology of anti-neutrophil cytoplasmic antibody (ANCA) mediated-vasculitis (AAV) with glomerulonephritis (ANCA GN). Different macrophage phenotypes are expected to play distinct roles in ANCA GN. Macrophages expressing CD163 and CD206 are found in lesions associated with ANCA GN. Hence, we aimed to investigate the clinicopathological significance of CD206 and CD163 in ANCA GN in a multicenter retrospective cohort study. MATERIAL AND METHODS: Patients with ANCA-associated vasculitis, with clinical data, serum and urine samples were included from three cohorts. Serum soluble CD206 (ssCD206) and urinary soluble CD163 (usCD163) levels were measured. Human kidney tissue samples (n = 53) were stained for CD206 and CD163 using immunohistochemistry and immunofluorescence, and findings were correlated with clinical and pathological data. RESULTS: In total, 210 patients were included (i.e., ANCA GN, n = 134; AAV without GN, n = 24; AAV in remission n = 52). Increased levels of both ssCD206 and usCD163 were seen in ANCA GN. High levels of ssCD206 declined after reaching remission, however, ssCD206 did not improve the accuracy of usCD163 to detect ANCA GN. Soluble markers correlated with histopathological findings. CD163+CD206- macrophages were found in the glomerulus and may play pivotal roles in glomerulonephritis, whereas CD206+CD163- and CD206+CD163+ macrophages were located tubulointerstitially and likely play a more prominent role in ANCA-associated tubulointerstitial inflammation. In ANCA GN patients increasing levels of ssCD206 increased the risk for end-stage renal disease and mortality. CONCLUSIONS: Our results confirm and extend the notion that CD206+ and CD163+ macrophages are prominent components of the cellular infiltrate in ANCA GN. We found distinct macrophage phenotypes that may play distinct roles in the immunopathology of ANCA GN and elaborate on a potential mechanism underlying the findings of this study. usCD163 remains an excellent marker to detect active ANCA GN, whereas ssCD206 seems a more prominent marker for risk prediction.

The natural course of pregnancies in women with primary atypical haemolytic uraemic syndrome and asymptomatic relatives.

Pregnancy has been linked to various microangiopathies, including primary atypical haemolytic uraemic syndrome (aHUS). Complement dysregulation, often linked to rare variants in complement genes, is key for primary aHUS to manifest and may play a role in pregnancy complications of the mother and fetus. The burden of such complications is unknown, making counselling of women with primary aHUS and asymptomatic relatives difficult. We analyzed the maternal and fetal outcomes of 39 pregnancies from 17 women with primary aHUS and two asymptomatic relatives. Seven out of 39 pregnancies were complicated by pregnancy-associated aHUS. Five out of 32 pregnancies not linked to pregnancy-associated aHUS were complicated by pre-eclampsia or HELLP. Rare genetic variants were identified in 10 women (asymptomatic relatives, n = 2) who had a total of 14 pregnancies, including 10 uncomplicated pregnancies. Thirty-five out of 39 pregnancies resulted in live birth. Eight out of 19 women had progressed to end-stage kidney disease, with an incidence of 2·95 (95% confidence interval, 1·37-5·61) per 100 person-years after the first pregnancy. Thus, we emphasized the frequency of successful pregnancies in women with primary aHUS and asymptomatic relatives. Pregnancies should be monitored closely. Rare genetic variants cannot predict the risk of a given pregnancy.

C5b9 Formation on Endothelial Cells Reflects Complement Defects among Patients with Renal Thrombotic Microangiopathy and Severe Hypertension.

Background Severe hypertension can induce thrombotic microangiopathy (TMA) in the renal vasculature, the occurrence of which has been linked to mechanical stress to the endothelium. Complement defects may be the culprit of disease in patients who present with severe renal disease and often progress to ESRD, despite BP control.Methods We studied a well defined cohort of 17 patients with hypertension-associated TMA to define the prevalence of complement defects by a specific ex vivo serum-based microvascular endothelial cell assay.Results Compared with normal human serum and samples from patients with hypertensive arterionephrosclerosis, 14 of 16 (87.5%) serum samples collected at presentation from 16 patients with hypertension-associated TMA induced abnormal C5b9 formation on microvascular endothelial cells. We detected rare variants in complement genes in eight of 17 (47%) patients. ESRD occurred in 14 of 17 (82%) patients, and recurrent TMA after transplant occurred in seven of 11 (64%) donor kidneys. Eculizumab improved the renal function in three patients and prevented TMA recurrence in an allograft recipient.Conclusions These observations point to complement defects as the key causative factor of ESRD and recurrent TMA after transplant in patients presenting with severe hypertension. Complement defects can be identified by measurements of complement activation on microvascular endothelial cells, which should substantially influence treatment and prognosis.

Impact of MPO-ANCA-mediated oxidative imbalance on renal vasculitis.

Glomerulonephritis is a severe complication of microscopic polyangiitis (MPA), a small-vessel vasculitis associated with anti-myeloperoxidase antibodies (MPO-ANCA). We previously showed the pathogenic effects of MPO-ANCA that activate MPO to trigger an oxidative burst mainly through HOCl production, contributing to endothelial injury and lung fibrosis. The aim of this study was to investigate the relationship between MPO-induced oxidative stress, anti-oxidant defenses and renal histological lesions in MPA patients. We therefore analyzed histological data from a prospective cohort of ANCA-associated glomerulonephritis. Serum-mediated HOCl production, advanced oxidation protein products (AOPP), and thiol concentration in sera were determined. From 38 patients included, histological classification noted 50% focal glomerulonephritis, 15.8% crescentic-glomerulonephritis, and 34.2% mixed-glomerulonephritis. MPA patients' sera displayed higher HOCl production by MPO ( P < 0.001), higher AOPP ( P < 0.001) and thiol ( P < 0.01) levels, compared with healthy subjects. The presence of cellular crescents was associated with higher serum-mediated HOCl production ( P = 0.049) and lower thiol levels ( P = 0.022) at disease onset. Higher thiol concentrations were associated with focal glomerulonephritis ( P = 0.042), less interstitial fibrosis ( P = 0.039) and hyalinosis ( P = 0.066). In remission, HOCl production was decreased ( P < 0.01), and thiol concentration remained high ( P = 0.39). Our findings suggest that HOCl production by activated MPO could contribute to the very early stage of glomerulonephritis, whereas thiol may exert a protective effect against the development of renal vasculitis and glomerulosclerosis. This study highlights the importance of oxidative defenses to counteract the process of MPO-ANCA associated glomerulonephritis.

Patients with hypertension-associated thrombotic microangiopathy may present with complement abnormalities.

Thrombotic microangiopathy (TMA) is a pattern of endothelial damage that can be found in association with diverse clinical conditions such as malignant hypertension. Although the pathophysiological mechanisms differ, accumulating evidence links complement dysregulation to various TMA syndromes and in particular the atypical hemolytic uremic syndrome. Here, we evaluated the role of complement in nine consecutive patients with biopsy-proven renal TMA attributed to severe hypertension. Profound hematologic symptoms of TMA were uncommon. In six out of nine patients, we found mutations C3 in three, CFI in one, CD46 in one, and/or CFH in two patients either with or without the risk CFH-H3 haplotype in four patients. Elevated levels of the soluble C5b-9 and renal deposits of C3c and C5b-9 along the vasculature and/or glomerular capillary wall, confirmed complement activation in vivo. In contrast to patients without genetic defects, patients with complement defects invariably progressed to end-stage renal disease, and disease recurrence after kidney transplantation seems common. Thus, a subset of patients with hypertension-associated TMA falls within the spectrum of complement-mediated TMA, the prognosis of which is poor. Hence, testing for genetic complement abnormalities is warranted in patients with severe hypertension and TMA on renal biopsy to adopt suitable treatment options and prophylactic measures.

Detection of antineutrophil cytoplasmic antibodies (ANCAs): a multicentre European Vasculitis Study Group (EUVAS) evaluation of the value of indirect immunofluorescence (IIF) versus antigen-specific immunoassays.

OBJECTIVE: This multicentre study was performed to evaluate the diagnostic accuracy of a wide spectrum of novel technologies nowadays available for detection of myeloperoxidase (MPO) and proteinase 3 (PR3)-antineutrophil cytoplasmic antibodies (ANCAs). METHODS: Sera (obtained at the time of diagnosis) from 251 patients with ANCA-associated vasculitis (AAV), including granulomatosis with polyangiitis and microscopic polyangiitis, and from 924 disease controls were tested for the presence of cytoplasmic pattern/perinuclear pattern and atypical ANCA (A-ANCA) by indirect immunofluorescence (IIF) (at two sites) and for the presence of PR3-ANCA and MPO-ANCA by eight different immunoassays. RESULTS: The area under the curve (AUC) of the receiver operating characteristic curve to discriminate AAV from controls was 0.923 (95% CI 0.902 to 0.944) and 0.843 (95% CI 0.814 to 0.871) for the two IIF methods. For the antigen-specific immunoassays, the AUC varied between 0.936 (95% CI 0.912 to 0.960) and 0.959 (95% CI 0.941 to 0.976), except for one immunoassay for which the AUC was 0.919 (95% CI 0.892 to 0.945). CONCLUSIONS: Our comparison of various ANCA detection methods showed (i) large variability between the two IIF methods tested and (ii) a high diagnostic performance of PR3-ANCA and MPO-ANCA by immunoassay to discriminate AAV from disease controls. Consequently, dual IIF/antigen-specific immunoassay testing of each sample is not necessary for maximal diagnostic accuracy. These results indicate that the current international consensus on ANCA testing for AAV needs revision.

A multicentre study to improve clinical interpretation of proteinase-3 and myeloperoxidase anti-neutrophil cytoplasmic antibodies.

Objective: The objective of this multicentre study was to improve the clinical interpretation of PR3- and MPO-ANCAs as an adjunct for the diagnosis of ANCA-associated vasculitis (AAV) by defining thresholds and test result intervals based on predefined specificities and by calculating test result interval-specific likelihood ratios (LRs). Methods: Eight different PR3- and MPO-ANCA immunoassays from seven companies were evaluated using 251 diagnostic samples from AAV patients and 924 diseased controls. Results: Thresholds for antibody levels were determined based on predefined specificities (95, 97.5, 99 and 100%) and used to delimit test result intervals. Test result interval-specific LRs were determined. For all assays, the LR for AAV increased with increasing antibody level. For all but one immunoassay, high antibodies levels (associated with LR >55) were found in a substantial fraction (>65%) of patients. The area under the curve (AUC) of receiver operating characteristics analysis of a diagnostic approach in which positive results were confirmed by IIF or another immunoassay was not substantially higher than the AUC of performing immunoassay only. The highest AUC was found when immunoassay was combined with another immunoassay or with IIF. Conclusion: To diagnose AAV based on PR3- and MPO-ANCA, it is useful to define thresholds for antibody levels and to assign test result interval-specific LRs. Higher antibody levels are associated with a higher likelihood for disease. Such information improves clinical interpretation.