Antineutrophil cytoplasmic antibody (ANCA) testing: Audit from a clinical immunology laboratory

Diagnostic accuracy of ANCA serology in ANCA-associated vasculitis with renal involvement

BACKGROUND

Pauci-immune glomerulonephritis (GN) due to antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a common cause of crescentic GN. Despite advances in treatment, rates of mortality and progression to end-stage kidney disease remain high. Renal involvement is diagnosed by histological examination of kidney tissue. Serum ANCAs play a significant role in AAV; however, the value of serum ANCA quantification to predict renal involvement is not well-established.

AIM

We aimed to evaluate the diagnostic accuracy of serum ANCA titres in diagnosing AAV with renal involvement.

METHODS

We conducted a retrospective study of consecutive native kidney biopsies reported at our centre from 2016 to 2021. We included all adults who had both a kidney biopsy and ANCA serology. ANCA serology was tested using indirect immunofluorescence with reporting of titres. Antibodies to proteinase 3 and myeloperoxidase were measured using a chemiluminescent immunoassay.

RESULTS

Eight hundred and forty-eight native kidney biopsies were reported during the study period. Five hundred and seven cases were included. The biopsy prevalence of pauci-immune GN in paired samples was 41/507 (8.1%). Most of the cohort had haematuria (66.6%), proteinuria (93.4%) and/or acute kidney injury (65.0%). A positive ANCA at any titre demonstrated a sensitivity of 97.6% and a specificity of 71.2% for a diagnosis of pauci-immune GN. The area under the curve for the receiver operator characteristic was 0.93 (95% confidence interval [CI]: 0.89-0.97). A cutoff ANCA titre of 1:160 provided the optimum balance between a sensitivity of 75.6% (95% CI: 59.7%-87.6%) and a specificity of 94.0% (95% CI: 91.6%-96.0%).

CONCLUSIONS

ANCA titres are highly predictive of pauci-immune GN in the appropriate context. While serum ANCA quantitation may not replace renal biopsy, reporting will assist in the decision to start treatment early for patients with organ or life-threatening disease.

Overlap syndrome of systemic sclerosis with antineutrophil cytoplasmic antibody-associated vasculitis according to 2022 ACR/EULAR criteria

BACKGROUND/AIMS

This study applied the 2022 American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR) criteria for antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) to patients with systemic sclerosis (SSc) and investigated the frequency of overlap syndrome of SSc and AAV (SSc-AAV-OS).

METHODS

Among the 232 patients diagnosed with SSc, 105 with signs suggestive of small- or medium-vessel vasculitis, which were defined as the present of interstitial lung disease (ILD), peripheral neuropathy, or suspected renal vasculitis, were included in this study and analyzed.

RESULTS

Among the 105 SSc patients, the detection rate of ANCA was 19.0%. When the 2022 ACR/EULAR criteria were applied, the frequency of SSc-AAV-OS was 20.0%, which was much higher than 1.7% reported with previous criteria for AAV. ANCA positivity contributed to the reclassification of SSc-AAV-OS more than ANCA negativity in SSc patients with signs suggestive of small- or medium-vessel vasculitis.

CONCLUSION

The frequency of SSc-AAV-OS in SSc patients with signs suggestive of small- or medium-vessel vasculitis at diagnosis was 20.0%. Therefore, we suggest that physicians should perform ANCA tests in SSc patients exhibiting signs suggestive of small- or medium-vessel vasculitis and apply the new criteria for AAV.

Modified Body Mass Index at Diagnosis is a Useful Predictor of Mortality in Patients With Antineutrophil Cytoplasmic Antibody-associated Vasculitis

Objective

We investigated whether modified body mass index (mBMI) at diagnosis could predict all-cause mortality during follow-up in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV).

Methods

The medical records of 203 AAV patients with BMI ≥18.5 kg/m2 were reviewed. mBMI was calculated using an equation mBMI=BMI (kg/m2)×serum albumin (g/L). All-cause mortality was considered as a poor outcome, and the follow-up duration based on all-cause mortality was defined as the period from AAV diagnosis to death for deceased patients, and the period from AAV diagnosis to the last visit for surviving patients.

Results

The median age was 59.0 years (35.5% were male). The median BMI and mBMI were 22.8 kg/m2 and 813.2 kg · g/m2 · L. Twenty-five patients (12.3%) died. mBMI was well correlated with age, BVAS, FFS, erythrocyte sedimentation rate and C-reactive protein at diagnosis. Deceased patients exhibited significantly lower mBMI at diagnosis compared to surviving patients. AAV patients mBMI ≤570.1 kg · g/m2 · L showed a significantly higher frequency of all-cause mortality (38.5% vs. 8.5%), and furthermore, exhibited a significantly higher risk for all-cause mortality than those with mBMI >570.1 kg · g/m2 · L (RR 6.750). mBMI ≤570.1 kg · g/m2 · L showed a significantly lower cumulative patients' survival rate than those with mBMI >570.1 kg · g/m2 · L. In the multivariable Cox hazards model analysis, either serum albumin or mBMI was significantly associated with all-cause mortality in AAV patients.

Conclusion

In conclusion, mBMI ≤570.1 kg · g/m2 · L at diagnosis may be a useful predictor of all-cause mortality during follow-up additionally to serum albumin in AAV patients.

Association Between Idiopathic Cutaneous Leukocytoclastic Angiitis and ANCA-negative Microscopic Polyangiitis

Objective

This study retrospectively reviewed the process of classifying antineutrophil cytoplasmic antibody (ANCA)-negative granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) in a cohort of patients with ANCA-associated vasculitis (AAV), and investigated the association between recurrent idiopathic cutaneous leukocytoclastic angiitis and ANCA-negative MPA.

Methods

The medical records of 242 patients with AAV were retrospectively reviewed Of 49 patients with ANCA-negative AAV, 24 patients with ANCA-negative eosinophilic GPA (EGPA) were excluded, because ANCA positivity or negativity is not critical in classifying EGPA Ultimately, 25 patients with ANCA-negative GPA and MPA were analysed in this study The classification of GPA and MPA were based on the 2007 European Medicines Agency algorithm for AAV.

Results

The median age of patients with ANCA-negative GPA and MPA was 540 years and 24% were male Of the 25 patients without ANCA, 8 patients were classified as GPA and 17 as MPA Eight patients with ANCA-negative GPA were easily confirmed as definitive GPA Fourteen of the 17 patients ANCA-negative MPA were classified as MPA based on histological features suggestive of AAV without granuloma formation and the absence of surrogate markers for GPA Meanwhile, three of the patients that were ANCA-negative exhibited only recurrent idiopathic cutaneous leukocytoclastic angiitis without other major organs affected and thus were classified as possible MPA Within one year, they were classified as definitive MPA based on ANCA positivity and/or renal histology.

Conclusion

Recurrent idiopathic cutaneous leukocytoclastic angiitis may be associated with ANCA-negative MPA in patients who exhibit cutaneous necrotising vasculitis.

Management of Severe Oral Inflammatory Conditions in Dogs and Cats

Severe oral inflammatory disease is not uncommon in the mouths of canine and feline patients. An approach to oral diagnosis is offered. This article discusses a brief review of important points in the oral diagnosis and management of main canine (canine chronic ulcerative stomatitis (CCUS), eosinophilic stomatitis, and Wegener's granulomatosis (WG)) and feline diseases (feline gingivostomatitis/caudal stomatitis, oral eosinophilic lesions, pyogenic granuloma, and autoimmune diseases with oral manifestations), and-whereby possible-information about the current understanding of disease pathogenesis and treatment is offered.

Unclassifiable repeated antineutrophil cytoplasmic antibody (ANCA) positivity in diseases other than ANCA-associated vasculitis

BACKGROUND AND OBJECTIVE

Antineutrophil cytoplasmic antibody (ANCA) is a specific autoantibody for ANCA-associated vasculitis (AAV). However, ANCA can be detected in various diseases other than AAV. Hence, in this study, we investigated and provided the name of diseases with repeated ANCA positivity and the frequency of each disease other than AAV.

METHODS

We retrospectively screened the results of the tests of ANCA in 26,499 patients using the Clinical Data Repository System and included in this study only 173 patients with repeated ANCA positivity more than twice. 'Unclassifiable ANCA' was defined when ANCA was detected in patients with diseases other than AAV. 'Unclassifiable repeated ANCA' was also defined when unclassifiable ANCA was successively detected more than twice.

RESULTS

Among rheumatic and autoimmune diseases, the most common disease with unclassifiable repeated ANCA was vasculitis undetermined (21.0%). In terms of cardiovascular and cerebrovascular diseases, the most common disease with unclassifiable repeated ANCA was atherosclerotic heart disease (12.1%). In terms of disorders in liver, kidneys and lungs, the most common disease with unclassifiable repeated ANCA was chronic kidney disease (51 cases, 29.5%). In addition, among infections with confirmed infectious pathogens, the most common pathogen with unclassifiable repeated ANCA was varicella-zoster virus (6.9%) followed by Candida (4.6%).

CONCLUSION

Overall, regardless of category, the common diseases with unclassifiable repeated ANCA were chronic kidney disease followed by interstitial lung disease and vasculitis undetermined. Thus, we carefully suggest that physicians should pay more attention to the development of AAV or vasculitis other than AAV and, furthermore, kidneys and lungs should be monitored regularly and closely in patients with unclassifiable repeated ANCA.

Anca-positive vasculitis with full-house nephropathy, an unusual association: a case report and review of literature

Rapidly progressive glomerulonephritis is a medical emergency, with mortality around 20%. It is characterized by crescent glomerulonephritis and progressive loss of kidney function, hematuria, and proteinuria. Its classification is given by immunofluorescence detection of antibodies against glomerular basement membrane (Anti-MBG), immunocomplexes, or pauci-immune pattern. Its etiology should be based on clinical findings, immunological profile, age, sex, and histopathological characteristics. We present a case of a 27-year-old woman with symptoms consistent with rapidly progressive glomerulonephritis and biopsy findings of a full-house kidney nephropathy, with an early fatal outcome. An association of low incidence, as it is a case with a full-house pattern, and an autoimmune profile for negative systemic lupus erythematosus makes this a rare case. ANCA-associated vasculitis with full-house kidney disease was diagnosed, an unusual condition with up to 3% presentation and few reports in the literature, highlighting the importance of its reporting and contribution to the literature.

The value of anti-neutrophil cytoplasmic antibodies (ANCA) testing for the diagnosis of ANCA-associated vasculitis, a systematic review and meta-analysis

The testing of anti-neutrophil cytoplasmic antibodies (ANCA) takes an important place in the diagnostic workup to ANCA-associated vasculitis (AAV). Nowadays, it is recommended to screen for the presence of PR3 and MPO specific antibodies first using immunoassay, without the need for ANCA measurement by indirect immunofluorescence (IIF). A literature search was performed to assess the diagnostic test value of ANCA IIF and PR3- and MPO-antibody immunoassay to diagnose AAV. This meta-analysis shows that the c-ANCA testing by IIF has a pooled sensitivity of 75.2% and a pooled specificity of 98.4%. For PR3-antibody immunoassay, the pooled sensitivity depended on the immunoassay method used, and ranged from 79.8% to 86.6%, whereas the pooled specificity ranged from 96.8% to 98.3%. For both p-ANCA IIF and MPO-antibody immunoassay (all methods) sensitivity varied considerably showing pooled values of respectively 46.3% and 58.1%, whereas respective pooled specificity was 91.4% and 95.6%. These findings support the 2017 international consensus that primary anti-PR3 and anti-MPO screening by immunoassay, based on superior immunoassay sensitivity without the need for IIF ANCA testing, improves the diagnostic workup of AAV.

Clinical significance of positive anti-neutrophil cytoplasmic antibodies without evidence of anti-neutrophil cytoplasmic antibodies-associated vasculitis

AIM

Anti-neutrophil cytoplasmic antibodies (ANCA) have a role in the diagnostic workup of ANCA-associated vasculitis. However, the clinical significance of positive ANCA in the absence of vasculitis is yet to be determined. Therefore, we sought to investigate the clinical spectrum and rate of patients with a positive ANCA without evidence of vasculitis.

METHODS

Retrospective analysis of patients positive for cytoplasmic ANCA (C-ANCA) and proteinase 3 (PR3) or P-ANCA and myeloperoxidase (MPO) between 2007 and 2016 in the Chaim Sheba Medical Center, Israel. The proportion of patients who had no evidence of vasculitis among all patients with a positive C-ANCA/PR3 or P-ANCA/MPO was calculated according to tertiles of enzyme-linked immunosorbent assay (ELISA) antibody levels.

RESULTS

Among 113 patients who tested positive for C-ANCA/PR3 or P-ANCA/MPO, 68 (60.1%) had no evidence of vasculitis. ELISA antibody titers were significantly higher among patients with vasculitis than those without (6.2 vs 3.2, for C-ANCA/PR3 and 5.4 vs 2.6 for P-ANCA/MPO, P < 0.05). The proportion of patients without vasculitis among all patients with a positive C-ANCA/PR3 and among all patients with a positive P-ANCA/MPO declined in parallel to the increases in ELISA antibody level tertiles (96%, 57% and 22% in the 1st, 2nd and highest tertiles, respectively, for patients with C-ANCA/PR3 patients and 100%, 66% and 20% in the 1st, 2nd and highest tertiles, respectively, for patients with P-ANCA/MPO).

CONCLUSION

A significant proportion of patients with a positive C-ANCA/PR3 or P-ANCA/MPO do not have evidence of vasculitis, particularly those with low-medium ELISA antibody titers. Using a higher threshold of ANCA titers may be required to improve specificity.