New kidney risk score shows strong predictive power in AAV study
Study compares three scoring systems used to estimate kidney risk
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A risk score that combines blood tests and kidney biopsy findings performed among the strongest tools for predicting kidney failure in people with ANCA-associated vasculitis (AAV), a small study suggests.
The analysis also showed that all three risk scoring systems evaluated remained linked to the risk of kidney failure even after accounting for differences in treatments, “further reinforcing their role in treatment decision-making,” the researchers wrote.
The results also suggest that using biopsy-based scores alongside scores that combine biopsy and blood test data “may improve risk stratification and support more personalized treatment decisions, particularly in patients with intermediate risk,” the researchers wrote.
Kidney involvement worsens prognosis in AAV
The study, “Comparative performance of renal histological scores in predicting kidney outcomes in ANCA-associated vasculitis,” was published in Nefrología by researchers in Portugal.
AAV is a group of rare diseases marked by inflammation and damage to small blood vessels, typically caused by self-reactive antibodies called ANCAs. AAV symptoms can vary depending on which organs are affected, but kidney problems are common.
Kidney involvement is generally linked to a poorer AAV prognosis because the disease can progress to kidney failure. In such cases, patients may need dialysis, a treatment that filters waste from the blood when the kidneys can no longer do so.
“Therefore, identifying accurate predictors of kidney outcome at the time of diagnosis remains a clinical priority to guide treatment decisions,” the researchers wrote.
“Several clinical and [kidney tissue-related] factors have been associated with long‑term kidney outcomes,” and “different scoring systems have been developed to inform about the risk of [kidney failure] in AAV,” the team wrote.
However, these scoring systems have rarely been compared directly, and it remains unclear whether they provide complementary information about a patient’s risk.
Researchers compare three kidney risk scores
With this in mind, the researchers compared three commonly used scoring systems designed to estimate the risk of kidney failure: the Mayo Clinic Chronicity Score (MCCS), the Renal Risk Score (RRS), and the Improved Kidney Risk Score (AKRiS). The study included 53 adults with AAV and kidney involvement, about 56.6% of whom were men.
The MCCS relies only on findings from a kidney biopsy, a test in which a small sample of kidney tissue is examined under a microscope. The RRS combines biopsy findings with the estimated glomerular filtration rate (eGFR), a measure of kidney function calculated using creatinine levels in the blood.
The AKRiS was developed as a modification of the RRS. It uses blood creatinine levels instead of eGFR, adjusts the weight given to certain biopsy findings, and adds a fourth risk category. In this study, it showed stronger predictive performance than the RRS.
All participants had undergone a kidney biopsy to confirm AAV between 2013 and 2023 at a single center in Portugal. Their median age at diagnosis was 65, and they were followed for a median of 42 months, or about 3.5 years.
At diagnosis, many patients had elevated blood creatinine and protein in the urine, both signs of kidney damage. Nearly one-third (32.1%) required kidney replacement therapy, such as dialysis, at presentation. About one-quarter (22.6%) later progressed to kidney failure after a median of five months. Seven patients (13.2%) died after a median follow-up of 57.5 months, or nearly five years.
Higher scores linked to greater kidney failure risk
Patients who progressed to kidney failure had significantly higher blood creatinine levels than those with less severe kidney disease (6.8 vs. 3.4 mg/dL). They were also significantly more likely to have more extensive kidney scarring and shrinkage of functional structures (75% vs. 26.8%) as well as scarring affecting more than half of the kidney’s filtering units (41.7% vs. 12.2%).
Participants who developed kidney failure also had significantly higher scores on all three risk tools — MCCS (6 vs. 3), RRS (5 vs. 4), and AKRiS (16.5 vs. 8). They were also more likely to need dialysis (58.3% vs. 24.4%) and plasma exchange therapy (33.3% vs. 7.3%), a treatment that removes harmful antibodies from the blood.
Statistical analysis accounting for several clinical factors showed that extensive kidney scarring and shrinkage of functional kidney structures was the strongest predictor of kidney failure, being significantly linked to a nine times higher risk.
The three risk scores were also independent predictors of kidney failure. Higher scores were significantly associated with a 25% to 57% higher risk of kidney failure.
When the researchers compared the three scores, AKRiS and MCCS showed the strongest predictive performance for kidney survival. AKRiS also demonstrated the best ability to differentiate kidney survival across low-, intermediate-, and high-risk groups.
Scores show similar patterns but differ in accuracy
Further analyses showed that the three scoring systems — MCCS, RRS, and AKRiS — generally agreed when identifying patients at low or high risk of kidney failure. However, the scores were less consistent for patients in intermediate-risk groups.
This study “reinforces the value of kidney biopsy in AAV,” the researchers wrote, adding that “the more recent AKRiS showed better discriminative ability, differentiating risk across all categories.”
Still, comparisons between MCCS, RRS, and AKRiS suggest “a complementary role for these scores in refining risk stratification, particularly among patients with intermediate risk,” the team wrote. As such, “Combined use of MCCS, RRS, and AKRiS may improve prognostic assessment in intermediate-risk groups.”
