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Objective: We describe the demographics, clinical features, disease course, and survival of polyarteritis nodosa (PAN) through an international collaboration (GLOBAL‐PAN). Methods: Patients with PAN were recruited between 1990 and 2020 from observational cohorts of nine countries across Europe, Japan, and North America. Eligibility was retrospectively defined using the European Medicines Agency classification algorithm. Patients with PAN related to hepatitis B virus (n = 12) and two monogenic diseases mimicking PAN, deficiency of adenosine deaminase 2 enzyme (n = 16) or familial Mediterranean fever (n = 11), were excluded. Data regarding organ involvement, relapse, disease‐related damage, and survival were analyzed. Results: Three hundred fifty‐eight patients (female:male ratio 174:184), including those with systemic PAN (sPAN, n = 282) and cutaneous PAN (n = 76), were included. Twenty‐five were pediatric onset. Mean ± SD age at diagnosis was 44.3 ± 18.1 years. Constitutional symptoms (71.5%), cutaneous involvement (70.5%), musculoskeletal findings (69.1%), and neurologic features (48.0%) were common manifestations. Among patients with sPAN, gastrointestinal involvement and proteinuria over 400 mg/day were reported in 52.2% and 11.2%, respectively. During a median (interquartile range) 59.6 (99.5) months of follow‐up, relapse occurred in 48.5% of patients. One, 5‐ and 10‐year survival rates for sPAN were 97.1%, 94.0%, and 89.0%, respectively. Predictors of death for sPAN included age ≥65 years at diagnosis, serum creatinine at diagnosis >140 μmol/L, gastrointestinal manifestations, and central nervous system (CNS) involvement. Conclusion: The spectrum of PAN remains a complex, multifaceted disease. Relapse is common. Age ≥65 years and serum creatinine >140 μmol/L at diagnosis, as well as gastrointestinal and CNS involvement, are independent predictors of death in sPAN. [ABSTRACT FROM AUTHOR]

Objective: Somatic variants in UBA1 cause VEXAS, a recently described, systemic autoinflammatory disease. Research on VEXAS has largely focused on highly symptomatic patients. We sought to determine the prevalence of canonical, VEXAS‐associated somatic variants and their disease penetrance in a diverse, unselected population. Methods: We analyzed clinical‐grade whole genome sequencing data from 245,368 participants in the All of Us Research Program. We compared persons carrying a canonical VEXAS‐associated somatic variant to age, sex, and ancestry matched controls across the domains of diagnoses, medications, and laboratory values. Results: 74 participants were identified who carry one VEXAS‐defining somatic variant, UBA1 c.121A>C, p.Met41Leu. The variant allele fraction ranged from 4.5% to 33%. No other canonical VEXAS‐associated variants were identified. Of the 74 carriers, 62 (84%) were women, 20 (27%) were African American, and 14 (19%) were American Admixed/Latino. There was no statistically significant association between case/control status and any VEXAS‐associated diagnosis code, medication prescription, or laboratory value. Conclusion: We report the largest cohort to date of persons with the VEXAS‐associated p.Met41Leu somatic variant. This cohort differed substantially from reported cohorts of patients with clinical VEXAS, having a higher proportion of persons who were young, female, and of diverse ancestry. Variant allele fractions were lower than reported in clinical VEXAS cohorts, and bioinformatic analysis detected no clinical manifestations of VEXAS. Thus, the UBA1 p.Met41Leu somatic variant displayed incomplete penetrance for VEXAS. Further study is needed to determine the natural history of VEXAS‐associated somatic variants in the predisease phase. [ABSTRACT FROM AUTHOR]

Objective: To assess whether vascular activity seen on 18F‐fluorodeoxyglucose–positron emission tomography (FDG‐PET) scan is associated with angiographic change in large vessel vasculitis (LVV). Methods: Patients with LVV were recruited into a prospective cohort. All patients underwent magnetic resonance angiography or computed tomography angiography and FDG‐PET imaging. Follow‐up imaging using the same imaging modalities was obtained ≥6 months later per a standardized imaging protocol. Arterial damage, defined as stenosis, occlusion, or aneurysm, and corresponding FDG uptake were evaluated in 17 arterial territories. On follow‐up, development of new lesions was recorded, and existing lesions were characterized as improved, worsened, or unchanged. Results: A total of 1,091 arterial territories from 70 patients with LVV (38 patients with Takayasu arteritis, 32 patients with giant cell arteritis) were evaluated. Over a median 1.6 years of follow‐up, new lesions developed only in 8 arterial territories in 5 patients with Takayasu arteritis. Arterial lesions improved in 16 territories and worsened in 6 territories. Most arterial territories that did not have vascular activity on FDG‐PET scan at baseline had no angiographic change over the follow‐up period (787 [99%] of 793). Few territories with baseline FDG‐PET activity had angiographic change over time (24 [8%] of 298), but of the territories that developed angiographic change, 80% had FDG‐PET activity at baseline. Within the same patient, an arterial territory with baseline FDG‐PET activity had significantly increased risk for angiographic change compared to a paired arterial territory without FDG‐PET activity (odds ratio 19.49 [95% confidence interval 2.44–156.02]; P < 0.01). Concomitant edema and wall thickening further increased risk for angiographic change. Conclusion: Development of angiographic change was infrequent in this cohort of patients with LVV. A lack of baseline FDG‐PET activity was strongly associated with stable angiographic disease. In cases of angiographic progression, change was preceded by the presence of FDG‐PET activity. [ABSTRACT FROM AUTHOR]

Objective: To develop and validate new classification criteria for Takayasu arteritis (TAK).Methods: Patients with vasculitis or comparator diseases were recruited into an international cohort. The study proceeded in six phases: (1) identification of candidate criteria items, (2) collection of candidate items present at diagnosis, (3) expert panel review of cases, (4) data-driven reduction of candidate items, (5) derivation of a points-based classification score in a development data set and (6) validation in an independent data set.Results: The development data set consisted of 316 cases of TAK and 323 comparators. The validation data set consisted of an additional 146 cases of TAK and 127 comparators. Age ≤60 years at diagnosis and imaging evidence of large-vessel vasculitis were absolute requirements to classify a patient as having TAK. The final criteria items and weights were as follows: female sex (+1), angina (+2), limb claudication (+2), arterial bruit (+2), reduced upper extremity pulse (+2), reduced pulse or tenderness of a carotid artery (+2), blood pressure difference between arms of ≥20 mm Hg (+1), number of affected arterial territories (+1 to +3), paired artery involvement (+1) and abdominal aorta plus renal or mesenteric involvement (+3). A patient could be classified as having TAK with a cumulative score of ≥5 points. When these criteria were tested in the validation data set, the model area under the curve was 0.97 (95% CI 0.94 to 0.99) with a sensitivity of 93.8% (95% CI 88.6% to 97.1%) and specificity of 99.2% (95% CI 96.7% to 100.0%).Conclusion: The 2022 American College of Rheumatology/EULAR classification criteria for TAK are now validated for use in research. [ABSTRACT FROM AUTHOR]

Objective: To develop and validate updated classification criteria for giant cell arteritis (GCA).Methods: Patients with vasculitis or comparator diseases were recruited into an international cohort. The study proceeded in six phases: (1) identification of candidate items, (2) prospective collection of candidate items present at the time of diagnosis, (3) expert panel review of cases, (4) data-driven reduction of candidate items, (5) derivation of a points-based risk classification score in a development data set and (6) validation in an independent data set.Results: The development data set consisted of 518 cases of GCA and 536 comparators. The validation data set consisted of 238 cases of GCA and 213 comparators. Age ≥50 years at diagnosis was an absolute requirement for classification. The final criteria items and weights were as follows: positive temporal artery biopsy or temporal artery halo sign on ultrasound (+5); erythrocyte sedimentation rate ≥50 mm/hour or C reactive protein ≥10 mg/L (+3); sudden visual loss (+3); morning stiffness in shoulders or neck, jaw or tongue claudication, new temporal headache, scalp tenderness, temporal artery abnormality on vascular examination, bilateral axillary involvement on imaging and fluorodeoxyglucose-positron emission tomography activity throughout the aorta (+2 each). A patient could be classified as having GCA with a cumulative score of ≥6 points. When these criteria were tested in the validation data set, the model area under the curve was 0.91 (95% CI 0.88 to 0.94) with a sensitivity of 87.0% (95% CI 82.0% to 91.0%) and specificity of 94.8% (95% CI 91.0% to 97.4%).Conclusion: The 2022 American College of Rheumatology/EULAR GCA classification criteria are now validated for use in clinical research. [ABSTRACT FROM AUTHOR]

Objective: To develop and validate classification criteria for microscopic polyangiitis (MPA).Methods: Patients with vasculitis or comparator diseases were recruited into an international cohort. The study proceeded in five phases: (1) identification of candidate items using consensus methodology, (2) prospective collection of candidate items present at the time of diagnosis, (3) data-driven reduction of the number of candidate items, (4) expert panel review of cases to define the reference diagnosis and (5) derivation of a points-based risk score for disease classification in a development set using least absolute shrinkage and selection operator logistic regression, with subsequent validation of performance characteristics in an independent set of cases and comparators.Results: The development set for MPA consisted of 149 cases of MPA and 408 comparators. The validation set consisted of an additional 142 cases of MPA and 414 comparators. From 91 candidate items, regression analysis identified 10 items for MPA, 6 of which were retained. The final criteria and their weights were as follows: perinuclear antineutrophil cytoplasmic antibody (ANCA) or anti-myeloperoxidase-ANCA positivity (+6), pauci-immune glomerulonephritis (+3), lung fibrosis or interstitial lung disease (+3), sino-nasal symptoms or signs (-3), cytoplasmic ANCA or anti-proteinase 3 ANCA positivity (-1) and eosinophil count ≥1×109/L (-4). After excluding mimics of vasculitis, a patient with a diagnosis of small- or medium-vessel vasculitis could be classified as having MPA with a cumulative score of ≥5 points. When these criteria were tested in the validation data set, the sensitivity was 91% (95% CI 85% to 95%) and the specificity was 94% (95% CI 92% to 96%).Conclusion: The 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology classification criteria for MPA are now validated for use in clinical research. [ABSTRACT FROM AUTHOR]

Objectives To evaluate the time-dependent effects of tocilizumab on vascular inflammation as measured by 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in GCA. Methods Patients with GCA treated with tocilizumab were selected from a prospective, observational cohort. Patients underwent FDG-PET at the baseline visit prior to initiation of tocilizumab and at subsequent follow-up visits performed at 6-month intervals. All imaging findings were interpreted blinded to clinical data. The PET vascular activity score (PETVAS) was used to quantify arterial FDG uptake. Wilcoxon signed rank test was used to compare change in PETVAS between visits. Linear regression was used to determine change in PETVAS over multiple timepoints. Results Twenty-five patients with GCA were included. All patients had physician-determined active vasculitis at the baseline visit by clinical assessment and FDG-PET interpretation. PETVAS was significantly reduced in association with tocilizumab treatment from the baseline to the most recent follow-up visit [24.0 (IQR 22.3–27.0) vs 18.5 (IQR 15.3–23.8); P  <0.01]. A significant reduction in PETVAS was observed over a two-year treatment period (P  <0.01 for linear trend), with a similar degree of improvement in both the first and second years of treatment. Repeat FDG-PET scans after tocilizumab discontinuation showed worsening PET activity in five out of six patients, with two patients subsequently experiencing clinical relapse. Conclusion Treatment of patients with GCA with tocilizumab was associated with both clinical improvement and reduction of vascular inflammation as measured by serial FDG-PET. Future clinical trials in GCA should study direct treatment effect on vascular inflammation as an outcome measure. [ABSTRACT FROM AUTHOR]

Objective: Little is known about temporal changes in nasal bacteria in granulomatosis with polyangiitis (GPA). This study was undertaken to examine longitudinal changes in the nasal microbiome in association with relapse in GPA patients. Methods: Bacterial 16S ribosomal RNA gene sequencing was performed on nasal swabs from 19 patients with GPA who were followed up longitudinally for a total of 78 visits, including 9 patients who experienced a relapse and 10 patients who remained in remission. Relative abundance of bacteria and ratios between bacteria were examined. Generalized estimating equation models were used to evaluate the association between bacterial composition and 1) disease activity and 2) levels of antineutrophil cytoplasmic antibody (ANCA) with specificity for proteinase 3 (PR3), adjusted for medication. Results: Corynebacterium and Staphylococcus were the most abundant bacterial genera across all nasal samples. Patients with quiescent disease maintained a stable ratio of Corynebacterium to Staphylococcus across visits. In contrast, in patients who experienced a relapse, a significantly lower ratio was observed at the visit prior to relapse, followed by a higher ratio at the time of relapse (adjusted P < 0.01). Species‐level analysis identified an association between a higher abundance of nasal Corynebacterium tuberculostearicum and 1) relapse (adjusted P = 0.04) and 2) higher PR3‐ANCA levels (adjusted P = 0.02). Conclusion: In GPA, significant changes occur in the nasal microbiome over time and are associated with disease activity. The occurrence of these changes months prior to the onset of relapse supports a pathogenic role of nasal bacteria in GPA. Our results uphold existing hypotheses implicating Staphylococcus as an instigator of disease and have generated a novel finding involving Corynebacterium as a potential mediator of disease in GPA. [ABSTRACT FROM AUTHOR]

Objectives To describe the clinical profile of Asian Indian patients with Takayasu's arteritis (TAK) and to compare clinical features and outcome of childhood-onset Takayasu's arteritis (cTAK) with adult-onset TAK (aTAK). Methods Data related to clinical features and response to treatment of patients with cTAK (age of onset <16 years) and aTAK from a large observational cohort in our tertiary care teaching hospital were noted and compared. Results Altogether, 602 patients (cTAK = 119; aTAK = 483) were studied. Patients with cTAK had a blunted female: male ratio; but fever, elevated acute phase reactants, involvement of abdominal aorta or its branches, hypertension, abdominal pain, elevated serum creatinine and cardiomyopathy were more common in cTAK as compared with aTAK. Patients with aTAK were more likely to have aortic-arch disease and claudication than cTAK. During follow-up, complete remission was more common in cTAK (87% vs 66%; P < 0.01), but subsequent relapses were equally common (30% vs 27%; P = 0.63). Independent associations of disease duration at presentation with disease extent [Disease Extent Index in TAK (DEI.Tak)] and damage [TAK Damage Score (TADS)] were observed (P ≤ 0.01). Moreover, 54% of patients with symptom duration of >5 years at presentation still continued to have elevated CRP suggesting continued and active inflammation warranting escalation or inititation of immunosuppression. Conclusion Patients with cTAK are more likely to have arterial disease below the diaphragm, systemic inflammation and achieve remission. Disease of the aortic arch is more common in patients with aTAK. Longer duration of symptoms prior to initiation of immunosuppression, thereby leading to extensive disease and damage, reflects ongoing disease activity as the rule rather than exception in untreated TAK. [ABSTRACT FROM AUTHOR]

Objective: To assess the validity and clinical utility of the Brief Illness Perception Questionnaire (BIPQ) to measure illness perceptions in multiple forms of vasculitis.Methods: Patients with giant cell arteritis (GCA), Takayasu arteritis (TA), antineutrophil cytoplasmic antibody-associated vasculitis (AAV), and relapsing polychondritis (RP) were recruited into a prospective, observational cohort. Patients independently completed the BIPQ, Multidimensional Fatigue Inventory (MFI), Medical Outcomes Study 36-item Short Form survey (SF-36), and a patient global assessment (PtGA) at successive study visits. Physicians concurrently completed a physician global assessment (PGA) form. Illness perceptions, as assessed by the BIPQ, were compared to responses from the full-length Revised Illness Perception Questionnaire (IPQ-R) and to other clinical outcome measures.Results: There were 196 patients (GCA = 47, TA = 47, RP = 56, AAV = 46) evaluated over 454 visits. Illness perception scores in each domain were comparable between the BIPQ and IPQ-R (3.28 vs 3.47, P = 0.22). Illness perceptions differed by type of vasculitis, with the highest perceived psychological burden of disease in RP. The BIPQ was significantly associated with all other patient-reported outcome measures (rho = |0.50-0.70|, P < 0.0001), but did not correlate with PGA (rho = 0.13, P = 0.13). A change in the BIPQ composite score of ≥ 7 over successive visits was associated with concomitant change in the PtGA. Change in the MFI and BIPQ scores significantly correlated over time (rho = 0.38, P = 0.0008).Conclusion: The BIPQ is an accurate and valid assessment tool to measure and monitor illness perceptions in patients with vasculitis. Use of the BIPQ as an outcome measure in clinical trials may provide complementary information to physician-based assessments. [ABSTRACT FROM AUTHOR]

Objective: Relapsing polychondritis (RP) is a systemic disease. Failure to recognize RP can lead to diagnostic delay and further complications, including death. This study was undertaken to identify clinical patterns in a prospective cohort of patients with RP. Methods: Patient subgroups were identified using latent class analysis based on 8 clinical variables: saddle‐nose deformity, subglottic stenosis, tracheomalacia, bronchomalacia, ear chondritis, tenosynovitis/synovitis, inflammatory eye disease, and audiovestibular disease. Model selection was based on Akaike's information criterion. Results: Seventy‐three patients were included in this study. Patients were classified into 1 of 3 subgroups: type 1 RP (14%), type 2 RP (29%), and type 3 RP (58%). Type 1 RP was characterized by ear chondritis (100%), tracheomalacia (100%), saddle‐nose deformity (90%), and subglottic stenosis (80%). These patients had the shortest median time to diagnosis (1 year), highest disease activity, and greatest frequency of admission to the intensive care unit and tracheostomy. Type 2 RP was characterized by tracheomalacia (100%) and bronchomalacia (52%), but no saddle‐nose deformity or subglottic stenosis. These patients had the longest median time to diagnosis (10 years) and highest percentage of work disability. Type 3 RP was characterized by tenosynovitis/synovitis (60%) and ear chondritis (55%). There were no significant differences in sex, race, or treatment strategies between the 3 subgroups. Conclusion: Our findings indicate that there are 3 subgroups of patients with RP, with differences in time to diagnosis, clinical and radiologic characteristics, and disease‐related complications. Recognizing a broader spectrum of clinical patterns in RP, beyond cartilaginous involvement of the ear and upper airway, may facilitate more timely diagnosis. [ABSTRACT FROM AUTHOR]

Objective: Diagnostic assessment in giant cell arteritis (GCA) is rapidly changing as vascular imaging becomes more available. This study was undertaken to determine if clinical GCA subsets have distinct profiles or reflect differential diagnostic assessments. Methods: Patients were recruited from an international cohort and divided into 4 subsets based on a temporal artery (TA) abnormality (positive TA biopsy [TAB] or halo sign on TA ultrasound [TA‐US]) and/or evidence of large vessel (LV) involvement on imaging: 1) both TA abnormality and LV involvement (TA+/LV+ GCA); 2) TA abnormality without LV involvement (TA+/LV− GCA); 3) LV involvement without TA abnormality (TA−/LV+ GCA); and 4) clinically diagnosed GCA without LV involvement or TA abnormality (TA−/LV− GCA). Results: Nine hundred forty‐one patients with GCA were recruited from 72 international study sites. Most patients received multiple forms of diagnostic assessment, including TAB (n = 705 [75%]), TA‐US (n = 328 [35%]), and LV imaging (n = 534 [57%]). Assessment using TAB, TA‐US, and LV imaging confirmed the diagnosis of GCA in 66%, 79%, and 40% of cases, respectively. GCA subsets had distinct profiles independent of diagnostic assessment strategies. TA+/LV− were the most common subset (51%), with a high burden of cranial ischemia. Those in the TA−/LV− subset (26%) had a high prevalence of cranial ischemia and musculoskeletal symptoms. Patients in the TA−/LV+ subset (12%) had prevalent upper extremity vascular abnormalities and a low prevalence of vision loss, and those in the TA+/LV+ subset (11%) were older and had a high prevalence of cranial ischemia, constitutional symptoms, and elevated acute‐phase reactant levels. Conclusion: Vascular imaging is increasingly incorporated into the diagnostic assessment of GCA and identifies clinical subsets of patients based on involvement of temporal and extracranial arteries. [ABSTRACT FROM AUTHOR]

Objective: Disease activity in large-vessel vasculitis (LVV) is traditionally assessed by clinical and serological variables rather than vascular imaging. This study determined the effect of treatment on 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) vascular activity in relation to clinical- and serologic-based assessments.Methods: Patients with giant cell arteritis (GCA) or Takayasu arteritis (TA) were prospectively evaluated at 6-month intervals in an observational cohort. Treatment changes were made at least 3 months before the followup visit and categorized as increased, decreased, or unchanged. Imaging (FDG-PET qualitative analysis), clinical, and serologic (erythrocyte sedimentation rate, C-reactive protein) assessments were determined at each visit and compared over interval visits.Results: Serial assessments were performed in 52 patients with LVV (GCA = 31; TA = 21) over 156 visits. Increased, decreased, or unchanged therapy was recorded for 36-, 23-, and 32-visit intervals, respectively. When treatment was increased, there was significant reduction in disease activity by imaging, clinical, and inflammatory markers (p ≤ 0.01 for each). When treatment was unchanged, all 3 assessments of disease activity remained similarly unchanged over 6-month intervals. When treatment was reduced, PET activity significantly worsened (p = 0.02) but clinical and serologic activity did not significantly change. Treatment of GCA with tocilizumab and of TA with tumor necrosis factor inhibitors resulted in significant improvement in imaging and clinical assessments of disease activity, but only rarely did the assessments both become normal.Conclusion: In addition to clinical and serologic assessments, vascular imaging has potential to monitor disease activity in LVV and should be tested as an outcome measure in randomized clinical trials. [ABSTRACT FROM AUTHOR]

Objective: To assess the clinical value of 18F‐fluorodeoxyglucose (FDG) positron emission tomography (PET) in a prospective cohort of patients with large vessel vasculitis (LVV) and comparator subjects. Methods: Patients with Takayasu arteritis and giant cell arteritis were studied, along with a comparator group consisting of patients with hyperlipidemia, patients with diseases that mimic LVV, and healthy controls. Participants underwent clinical evaluation and FDG‐PET imaging, and patients with LVV underwent serial imaging at 6‐month intervals. We calculated sensitivity and specificity of FDG‐PET interpretation for distinguishing patients with clinically active LVV from comparator subjects and from patients with disease in clinical remission. A qualitative summary score based on global arterial FDG uptake, the PET Vascular Activity Score (PETVAS), was used to study associations between activity on PET scan and clinical characteristics and to predict relapse. Results: A total of 170 FDG‐PET scans were performed in 115 participants (56 patients with LVV and 59 comparator subjects). FDG‐PET distinguished patients with clinically active LVV from comparator subjects with a sensitivity of 85% (95% confidence interval [95% CI] 69, 94) and a specificity of 83% (95% CI 71, 91). FDG‐PET scans were interpreted as active vasculitis in most patients with LVV in clinical remission (41 of 71 [58%]). Clinical disease activity status, disease duration, body mass index, and glucocorticoid use were independently associated with activity on PET scan. Among patients who underwent PET during clinical remission, future clinical relapse was more common in patients with a high PETVAS than in those with a low PETVAS (55% versus 11%; P = 0.03) over a median follow‐up period of 15 months. Conclusion: FDG‐PET provides information about vascular inflammation that is complementary to, and distinct from, clinical assessment in LVV. FDG‐PET scan activity during clinical remission was associated with future clinical relapse. [ABSTRACT FROM AUTHOR]

Objective. The aim of this study was to assess the clinical value of absolute eosinophil count, serum IgE, ESR and CRP as longitudinal biomarkers of disease activity and predictors of relapse in eosinophilic granulomatosis with polyangiitis (Churg-Strauss, EGPA). Methods. Patients were selected from an observational EGPA cohort. Absolute eosinophil count, IgE, ESR and CRP were measured quarterly. Disease activity was defined by validated assessment tools. The association of tests with disease activity was assessed via regression models, adjusting for repeated measures and treatment status. Survival analysis was used to determine if laboratory tests were predictive of the 3 month future flare risk. Results. Seventy-four per cent of 892 study visits in 141 patients occurred while patients were on treatment, mostly during remission or mild disease activity, defined as a BVAS for Wegener's granulomatosis (BVAS/WG) of 1 or 2. Correlations between absolute eosinophil count, IgE, ESR and CRP were mostly low or non-significant (r=-0.08 to 0.44). There were few weak associations with disease activity [absolute eosinophil count: OR) 1.01/100 U (95% CI 1.01, 1.02); ESR: OR 1.15/10mg/l increase (95% CI 1.04, 1.27)]. When BVAS/WG ≥1 defined active disease, the absolute eosinophil count [hazard ratio (HR) 1.01/ 100U(95% CI 1.01, 1.02)] was weakly predictive of flare. When BVAS/WG ≥3 defined active disease, ESR was weakly predictive of flare [HR 1.52/10 mm/h increase (95% CI 1.17, 1.67)]. Conclusion. The absolute eosinophil count, IgE, ESR and CRP have limitations as longitudinal biomarkers of disease activity or predictors of flare in EGPA. These findings suggest that novel biomarkers of disease activity for EGPA are needed. [ABSTRACT FROM AUTHOR]