Kidney involvement augurs worse ANCA-associated vasculitis outcome

Even in its early stages, the condition indicated poorer prognosis for patients

Lindsey Shapiro, PhD avatar

by Lindsey Shapiro, PhD |

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End-stage kidney disease (ESKD) that required dialysis or a kidney transplant was associated with an elevated risk of death among people with ANCA-associated vasculitis (AAV), compared to patients who didn’t develop the complication, research indicates.

A kidney transplant was associated with better prognosis compared to dialysis. On kidney biopsies, indicators of chronic kidney damage were associated with a higher risk of ESKD.

AAV patients with any kidney involvement, even in its early stages, were found to have worse survival than their peers in the general population.

“Early diagnosis of AAV is extremely important. Even milder forms of kidney involvement have an impact on the prognosis” the researchers wrote in “Long-term outcome of kidney function in patients with ANCA-associated vasculitis,” which was published in Nephrology Dialysis Transplantation.

AAV refers to a group of autoimmune disorders wherein the immune system mistakenly attacks small blood vessels. The kidneys are commonly affected since they contain many of them.

Severe manifestations of AAV include rapidly progressive glomerulonephritis — where the waste filtering units of the kidneys (glomeruli) become inflamed and damaged — that drive kidney failure and contribute to an elevated mortality risk.

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Kidney involvement and AAV prognosis

In the study, scientists estimated the frequency of ESKD among AAV patients and evaluated factors that predict ESKD and death in this patient group. Their analysis included data from 848 patients who’d participated in previous randomized controlled clinical trials by the European Vasculitis Society. The patients, who had a mean age of 58 when they were diagnosed, were followed for a median of nearly eight years.

Kidney involvement was detected in about three-quarters (76%) of patients at the time of their AAV diagnosis, with 107 people with ESKD needing dialysis, a blood filtering procedure used when the kidneys are failing and cannot do so on their own. The estimated incidence, or new cases, of ESKD after 15 years was 26.8%.

A total of 175 people developed ESKD during follow-up and required kidney replacement therapy, which involved dialysis for 140 people and a kidney transplant for 35. Of the 107 people who started out with ESKD, 37 regained kidney function at some point. Eleven needed subsequent dialysis.

The patients who developed ESKD were at a nearly three times higher risk of death than those who didn’t. Overall, 118 of the 175 people with ESKD died over follow-up, with higher mortality rates observed among those who had dialysis compared to those who had a transplant. While 78.6% of those on dialysis died, 22.8% of those who received a kidney transplant died.

ESKD patients with the granulomatosis with polyangiitis AAV subtype also had a better prognosis than those with microscopic polyangiitis.

Compared to people in the general population, people with AAV and kidney involvement had worse survival outcomes, even in the early stages of chronic kidney disease.

Final statistical analyses indicated older age (above 65), lower estimated glomerular filtration rate (eGFR) — reflective of lower filtering capacity of the kidneys — and lower hemoglobin, the protein that carries oxygen in red blood cells, were significant predictors of ESKD in AAV patients.

A subset of patients had available data from kidney biopsies. For those patients, a lower eGFR along with certain biopsy findings were also associated with the risk of ESKD, including a lower percentage of normal glomeruli and a higher degree of scar tissue buildup in the glomeruli.

“These findings highlight the need to diagnose patients with AAV in the early phases of the disease when there is less chronic damage,” wrote the researchers, who applied three different scoring systems to available biopsy images — the Berden Classification, the Renal Risk Score (RRS), and the Mayo Clinic Chronicity Score (MCCS) — to assess whether any could serve as biomarkers of a patient’s prognosis.

Patients classified as having the most severe kidney damage by any of these scoring systems were at an elevated risk of ESKD or death. The RRS was most able to predict prognosis, followed by MCCS.

“Additional studies are warranted to establish the usefulness of these classifications to guide therapeutical practice at various degrees of kidney involvement,” the researchers said.