Validation of the renal risk score for antineutrophil cytoplasmic antibody-associated glomerulonephritis in a Chinese population

The Improved Kidney Risk Score in ANCA-Associated Vasculitis for Clinical Practice and Trials

SIGNIFICANCE STATEMENT

Reliable prediction tools are needed to personalize treatment in ANCA-associated GN. More than 1500 patients were collated in an international longitudinal study to revise the ANCA kidney risk score. The score showed satisfactory performance, mimicking the original study (Harrell's C=0.779). In the development cohort of 959 patients, no additional parameters aiding the tool were detected, but replacing the GFR with creatinine identified an additional cutoff. The parameter interstitial fibrosis and tubular atrophy was modified to allow wider access, risk points were reweighted, and a fourth risk group was created, improving predictive ability (C=0.831). In the validation, the new model performed similarly well with excellent calibration and discrimination ( n =480, C=0.821). The revised score optimizes prognostication for clinical practice and trials.

BACKGROUND

Reliable prediction tools are needed to personalize treatment in ANCA-associated GN. A retrospective international longitudinal cohort was collated to revise the ANCA renal risk score.

METHODS

The primary end point was ESKD with patients censored at last follow-up. Cox proportional hazards were used to reweight risk factors. Kaplan-Meier curves, Harrell's C statistic, receiver operating characteristics, and calibration plots were used to assess model performance.

RESULTS

Of 1591 patients, 1439 were included in the final analyses, 2:1 randomly allocated per center to development and validation cohorts (52% male, median age 64 years). In the development cohort ( n =959), the ANCA renal risk score was validated and calibrated, and parameters were reinvestigated modifying interstitial fibrosis and tubular atrophy allowing semiquantitative reporting. An additional cutoff for kidney function (K) was identified, and serum creatinine replaced GFR (K0: <250 µ mol/L=0, K1: 250-450 µ mol/L=4, K2: >450 µ mol/L=11 points). The risk points for the percentage of normal glomeruli (N) and interstitial fibrosis and tubular atrophy (T) were reweighted (N0: >25%=0, N1: 10%-25%=4, N2: <10%=7, T0: none/mild or <25%=0, T1: ≥ mild-moderate or ≥25%=3 points), and four risk groups created: low (0-4 points), moderate (5-11), high (12-18), and very high (21). Discrimination was C=0.831, and the 3-year kidney survival was 96%, 79%, 54%, and 19%, respectively. The revised score performed similarly well in the validation cohort with excellent calibration and discrimination ( n =480, C=0.821).

CONCLUSIONS

The updated score optimizes clinicopathologic prognostication for clinical practice and trials.

Validation of a renal risk score in a cohort of children with ANCA-associated glomerulonephritis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is extremely rare in children. Renal involvement is a common and severe complication of AAV as it can cause end stage kidney disease (ESKD). ANCA renal risk score (ARRS) is helpful in predicting long-term ESKD in patients with ANCA-associated glomerulonephritis (AAGN). This retrospective study included 61 consecutive patients with kidney biopsy specimen-proven AAGN from Clinical Center for Children's Kidney Disease in China. Each patient was assessed by eGFR, normal glomeruli, and tubular atrophy/interstitial fibrosis, and the renal outcome was evaluated using the ARRS. Based on the ARRS, 27 (44.26%), 21 (34.43%), and 13 (21.31%) patients were divided into the low-risk, medium-risk, and high-risk groups, respectively. The median follow-up period was 46.36 (14.58-95.62) months. The high-risk group had worse renal outcomes than the low-risk group (p< 0.05) and the medium-risk group (p < 0.05). COX multivariate regression analysis showed that eGFR ≤ 15 ml/min/1.73 m2 (p = 0.015, Hazard Ratio (HR) = 9.574, 95% CI 4.205-25.187) and ARRS (p = 0.012, HR = 2.115, 95% CI 1.206-4.174) were independent risk factors for ESKD.The area under the curve for ESKD prediction of ARRS was 0.880, and the best cutoff value was 5.50. Delong test result showed that ARRS exhibited better predictive value for ESKD than the Berden classification (p < 0.001) and rapidly progressive glomerulonephritis (p < 0.001). This is the first study to investigate the value of the ARRS for predicting renal prognosis among Chinese children. The ARRS is a preferred index that can predict ESKD in Chinese children with AAGN.

Evaluation of three scoring systems for predicting renal prognosis in antineutrophil cytoplasmic antibody-associated glomerulonephritis

BACKGROUND

Antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (AAGN) is characterized by rapidly progressive glomerulonephritis, and timely initiation of treatment and evaluation is critical to prevent the progression of renal disease to end-stage renal disease (ESRD). The aim of this study was to evaluate predictive value of the renal risk score (RRS), Birmingham vasculitis activity score (BVAS), and renal vascular lesions (RVLs) score for renal prognosis in AAGN.

METHODS

A retrospective analysis of ninety-four patients diagnosed with AAGN after renal biopsy was performed. The RRS, BVAS, and RVLs score were evaluated in relation to clinicopathologic features and renal prognosis. A receiver operating characteristic curve (ROC) was used to evaluate their renal prognostic value.

RESULTS

The median follow-up time was 36 months. Thirty-eight patients progressed to ESRD. Survival analysis showed that renal prognosis worsened in the RRS group in order of low, medium, and high RRS (P < 0.05). Within the RVLs group, the renal prognosis of the groups with severe and moderate RVLs was worse than that of the group without RVLs (P = 0.012, P < 0.001), and the group with mild RVLs was close to that of the group without RVLs. ROC analysis showed that the AUC of RRS, BVAS, RVLs score, RVLs score combined with RRS (RVLs score & RRS, RR), RVLs score, and RRS combined with BVAS (RVLs score & RRS & BVAS, RRB) were 0.865, 0.624, 0.763, 0.910, and 0.942, respectively. The predictive power of RRB and RR was comparable and significantly better than the RRS, BVAS, and RVLs score. Based on simplicity and validity, RR was selected as the best predictor, and the relationship between RRS, RVLs score, and RR was calculated using a linear fit, resulting in the linear equation RR = -0.4766 + 0.1231 × RVLs score + 0.395 × RRS (P < 0.001).

CONCLUSIONS

In AAGN, the predictive power of RR for renal prognosis was superior to that of RRS, BVAS, and RVLs score. RR may serve as a new predictor of renal prognosis in AAGN.

Evaluation of a renal risk score for Japanese patients with ANCA-associated glomerulonephritis in a multi-center cohort study

Background

In patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis, prediction of renal survival should guide the choice of therapy, but a prediction of the histological classification has inconsistencies.

Objectives

To evaluate the usefulness of renal risk score (RRS) for Japanese patients with ANCA-associated glomerulonephritis (AAGN) and compare the prediction for end-stage renal disease (ESRD) between RRS and the histological classification.

Methods

We retrospectively analyzed 96 patients with AAGN who underwent a renal biopsy. Renal survival was categorized by RRS, and the histological classification was assessed separately. We compared the predictive values for RRS and the histological classification.

Results

The median observational period was 37.5 (interquartile range [IQR] 21.5-77.0) months. The median RRS point at the time of renal biopsy was 2 (IQR 0-7.8), and the patients were categorized into low- (n = 29), medium- (n = 43), and high-risk groups (n = 24) using RRS. As expected, the renal prognosis was the worst in the "high-risk" group and the best in the "low-risk" group. In the histological classification, the survival deteriorated progressively from "focal" (best) to "mixed," "crescentic," and "sclerotic" (worst) classes, different from the order in the original proposal for this system. Multivariable Cox regression analysis revealed that RRS was independently associated with ESRD. The difference in prediction for renal survival between RRS and the histological classification was not significant using area under receiver-operating-characteristic curves.

Conclusion

We evaluated the usefulness of RRS in Japanese patients with AAGN and found it a stable predictor of renal survival in such patients.

Histopathological prognostic factors in ANCA-associated glomerulonephritis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) are a group of multisystemic autoimmune diseases characterized by necrotizing inflammation of small vessels. Kidney involvement is frequent in granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA), and accounts for a significant proportion of the morbidity and mortality related to these diseases. Despite improvement in therapeutic management of ANCA-glomerulonephritis (ANCA-GN), end-stage kidney disease (ESKD) still occurs in up to 30% of affected patients within 5 years following diagnosis. Thus, identifying patients for whom aggressive immunosuppressive therapy will be more beneficial than deleterious is of great importance. Several clinical, biological and histological factors have been proposed as predictors of ESKD. The kidney biopsy is essential not only for the diagnosis, but also for evaluating renal prognosis. In this review, we discuss the prognostic value of renal lesions at the diagnosis of ANCA-GN by analyzing each compartment of the nephron. We also review existing ESKD risk classification in ANCA-GN and finally propose an example of a standardized pathology report that could be used in routine practice.

Assessment of Renal Risk Score and Histopathological Classification for Prediction of End-Stage Kidney Disease and Factors Associated With Change in eGFR After ANCA-Glomerulonephritis Diagnosis

Introduction

The “Renal Risk Score” (RRS) and the histopathological classification have been proposed to predict the risk of end-stage kidney disease (ESKD) in ANCA-associated glomerulonephritis (ANCA-GN). Besides, factors associated with kidney function recovery after ANCA-GN onset remain to be more extensively studied. In the present study, we analyzed the value of the RRS and of the histopathological classification for ESKD prediction. Next, we analyzed factors associated with eGFR change within the first 2 years following ANCA-GN diagnosis.

Materials and Methods

We included patients from the Maine–Anjou ANCA-associated vasculitis registry with at least 6 months of follow-up. The values of ANCA-GN, histopathological classification, and RRS, and the factors associated with eGFR variations between ANCA-GN diagnosis and 2 years of follow-up were assessed.

Results

The predictive values of the histopathological classification and RRS were analyzed in 123 patients. After a median follow-up of 42 months, 33.3% patients developed ESKD. The predictive value of RRS for ESKD was greater than that of the histopathological classification. Determinants of eGFR variation were assessed in 80/123 patients with complete eGFR measurement. The median eGFR increased from ANCA-GN diagnosis to month 6 and stabilized thereafter. The only factor associated with eGFR variation in our study was eGFR at ANCA-GN diagnosis, with higher eGFR at diagnosis being associated with eGFR loss (p<0.001).

Conclusion

The RRS has a better predictive value for ESKD than the histopathological classification. The main determinant of eGFR variation at 2 years was eGFR at ANCA-GN diagnosis. Thus, this study suggests that eGFR recovery is poorly predicted by histological damage at ANCA-GN diagnosis.