Histopathologic classification of anti-neutrophil cytoplasmic antibody-associated glomerulonephritis: achievements, limitations, and perspectives

Application of Diffusion Kurtosis Imaging and Blood Oxygen Level-Dependent Magnetic Resonance Imaging in Kidney Injury Associated with ANCA-Associated Vasculitis

OBJECTIVE

Functional magnetic resonance imaging (fMRI) has been applied to assess the microstructure of the kidney. However, it is not clear whether fMRI could be used in the field of kidney injury in patients with Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV).

METHODS

This study included 20 patients with AAV. Diffusion kurtosis imaging (DKI) and blood oxygen level-dependent (BOLD) scanning of the kidneys were performed in AAV patients and healthy controls. The mean kurtosis (MK), mean diffusivity (MD), and fractional anisotropy (FA) parameters of DKI, the R2* parameter of BOLD, and clinical data were further analyzed.

RESULTS

In AAV patients, the cortex exhibited lower MD but higher R2* values compared to the healthy controls. Medullary MK values were elevated in AAV patients. Renal medullary MK values showed a positive correlation with serum creatinine levels and negative correlations with hemoglobin levels and estimated glomerular filtration rate. To assess renal injury in AAV patients, AUC values for MK, MD, FA, and R2* in the cortex were 0.66, 0.67, 0.57, and 0.55, respectively, and those in the medulla were 0.81, 0.77, 0.61, and 0.53, respectively.

CONCLUSIONS

Significant differences in DKI and BOLD MRI parameters were observed between AAV patients with kidney injuries and the healthy controls. The medullary MK value in DKI may be a noninvasive marker for assessing the severity of kidney injury in AAV patients.

Clinicopathological Characteristics and Influencing Factors of Renal Vascular Lesions in Anti-neutrophil Cytoplasmic Autoantibody-Related Renal Vasculitis

The purpose of this study was to evaluate the clinicopathological features of different degrees of extraglomerular renal vascular lesions (RVLs) in patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated renal vasculitis and explore their clinical determinants. This is a retrospective study of 186 patients with ANCA-associated renal vasculitis diagnosed at the First Affiliated Hospital of Zhengzhou University from January 2014 to April 2019. The patients who met the inclusion criteria were divided into non-renal RVLs, mild RVLs, moderate RVLs, and severe RVLs. It was found that there were significant differences in serum creatinine (SCR), estimated glomerular filtration rate (eGFR), erythrocyte sedimentation rate (ESR), high-density lipoprotein (HDL), systolic blood pressure (SBP), the prevalence rate of hypertension, the proportion of normal glomeruli, and the proportion of sclerotic glomeruli and interstitial fibrosis integral. SCR and ESR are independent risk factors for RVLs. The participants were followed up for 1 year, and the progression to end-stage renal disease (ESRD) and death was defined as endpoint events. We found that the survival rate of patients without RVLs was significantly higher than that of patients with RVLs and that the RVLs were an independent risk factor for ESRD or death. Early intervention in the progression of RVLs can improve the prognosis.

Validation of a renal risk score in a cohort of ANCA-associated vasculitis patients with severe kidney damage

OBJECTIVE

To validate the renal risk score in a cohort of patients with advanced kidney damage.

METHODS

A total of 72 patients with biopsy-proven ANCA glomerulonephritis with >12 months of follow-up were studied. The renal risk score was calculated and evaluated by survival analysis for time of renal survival. Cohort-specific clinical, histopathologic, and post-treatment factors associated with renal survival were determined by Cox regression analysis.

RESULTS

Kidney biopsies were classified as focal, crescentic, mixed, and sclerotic classes in 6 (8%), 4 (6%), 25 (35%), and 37 (51%) patients, respectively. The 1-, 3-, and 5-year renal survival rates were 79%, 73%, and 68%, respectively. Patients were segregated by the risk score in low- (18%), medium- (47%), and high-risk (35%) groups. Patients in the low-risk group had 36-, 60-, and 84-month renal survival of 100%; those in the medium risk 85% (95% CI 72-92), 81% (95% CI 66-95), and 76% (95% CI 60-92), respectively; and those in the high risk 37% (95% CI 17-57), 26% (95% CI 7-45), and 18% (95% CI 1-36), respectively. Six (43%) of the 14 patients in the high-risk group recovered renal function after the initial episode, and 2 (14%) remained dialysis-free. Other parameters associated with renal survival included age, proteinuria, general symptoms, cellular crescents, glomerulosclerosis, tubulointerstitial lesions, best post-treatment eGFR, and renal relapses.

CONCLUSIONS

We validated the renal risk score as a prognostic tool in a cohort with predominantly mixed and sclerotic histologic categories. Since patients in the high-risk group still benefited from immunosuppressive therapy, this score should be used in conjunction with other predictive parameters to aid therapeutic decisions.Key Points• The ANCA renal risk score is validated in a cohort with advanced kidney damage.• Patients in the high-risk group still benefited from immunosuppressive therapy.• Parameters not included in the risk score are associated with renal survival and may be useful.

Prognostic Factors in Anti-Neutrophil Cytoplasmic Antibody-Associated Glomerulonephritis with Severe Glomerular Sclerosis: A National Registry-Based Cohort Study

Background

Classification of patients with anti-neutrophil cytoplasmic antibody-associated glomerulonephritis (ANCA-GN) into histological classes is useful for predicting a patient's risk of progression to end-stage renal disease (ESRD). However, even in the worst prognostic group, the 5-year end-stage renal disease-free survival rate is as high as 50%.

Objectives

To investigate those prognostic factors indicative of progression to ESRD in patients with ANCA-GN and sclerosing histology.

Methods

Patients from the Norwegian Kidney Biopsy Registry between 1991 and 2012 who had biopsy verified pauci-immune glomerulonephritis, positive ANCA serology, and sclerosing histology were included. Cases with ESRD during follow-up were identified via linkage with the Norwegian Renal Registry. Potential prognostic factors with relevant cut-offs were compared in patients with and without progression to ESRD during follow-up.

Results

Of 23 included patients, 10 progressed to ESRD. ESRD patients had a lower initial estimated glomerular filtration rate (eGFR; 21 versus 52 ml/min/1.73 m²) and a lower percentage of normal glomeruli (4% versus 15%). Five-year risks of ESRD with eGFR >15 versus ≤15 ml/min/1.73 m² were 77% and 15%, with percentage normal glomeruli >10% versus ≤10%, 83% and 39%.

Conclusions

eGFR and percentage of normal glomeruli are strong risk factors for ESRD in ANCA-GN with sclerosing histology.

Determinants of renal and patient outcomes in a Spanish cohort of patients with ANCA-associated vasculitis and renal involvement

The classification of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) remains controversial. The main objective of this study was to define the respective values of ANCA serotype-based classification, clinicopathological classification, and histopathological classification in predicting patient and renal outcomes in a Spanish cohort of patients with ANCA with specificity for myeloperoxidase, MPO-ANCA, versus ANCA with specificity for proteinase 3, PR3-ANCA. Two hundred and forty-five patients with ANCA-AAV and biopsy-proven renal involvement diagnosed between 2000 and 2104 were recruited in 12 nephrology services. Clinical and histologic data, renal outcomes, and mortality were analyzed. We applied the Chapel Hill Consensus Conference definition with categories for granulomatosis with the polyangiitis (GPA) and microscopic polyangiitis (MPA), the classification based on ANCA specificity, and the histopathological classification proposed in 2010. Eighty-two percent were MPO-ANCA positive and 18.0% PR3-ANCA positive. Altogether, 82.9% had MPA and 17.1% GPA. The median follow-up was 43.2 months (0.1-169.3). Neither ANCA-based serological nor clinical classification was predictive of renal outcomes or patient survival on bivariate or multivariate Cox regression analysis. Histopathological classification was found to predict development of end-stage renal disease (p = 0.005) in Kaplan-Meier analysis. ANCA specificity was more predictive of relapse than clinicopathological classification in multivariate analysis (HR 2.086; 95% CI 1.046-4.158; p = 0.037). In our Spanish cohort, a majority of patients had an MPO-ANCA-AAV. A classification based on ANCA specificity has a higher predictive value for relapse occurrence and could be used for decision-making with respect to induction treatment and maintenance therapies.