Chronic kidney disease (CKD) is a gradual loss of kidney function that can lead to fluid,
electrolyte and waste build-up in its advanced stages. Gout, a condition
marked by high levels of uric acid that can crystallize through the
body, can lead to CKD in some patients.
Could patients with chronic kidney disease benefit from therapies that lower their serum uric acid levels to reach a target goal associated with better organ function? A group of researchers set out to examine whether this therapy, widely used for gout treatment, help CKD patients who achieve the ACR target serum urate level of <6mg/dl.
That minimum target is associated with improvement in the signs and symptoms of gout, according to the 2012 ACR Guidelines for Management of Gout. They also wanted to find out if patients' CKD stage at the beginning of treatment would influence the benefits of urate-lowering therapy (ULT). First-line therapies for lowering urate levels are allopurinol and febuxostat.
"Progressive kidney disease leading to dialysis impacts patients on a daily basis and represents a major cost to the health care system," said Gerald Levy, MD, MBA, a rheumatologist at Kaiser Permanente in Downey, California, and a lead author of the study. "Controlling diabetes and hypertension are the primary tools to prevent end stage kidney disease. Normalizing serum uric acid level potentially is another tool to help prevent worsening kidney disease."
In this retrospective cohort study conducted from 2008 to 2014, the researchers identified 12,751 patients with serum urate levels of >7mg/dl. Patients' index date for the study was the first time they achieved this test result. In addition, patients included in the study had an estimated glomerular filtration rate (eGFR), a test used to measure kidney function and how well the kidneys are filtering blood, in the six months prior to that index date.
They also had to be ULT-naïve, 18 years of age or older, and have either CKD Stages 2, 3 or 4 at the index date. The researchers also only included patients who had continuous health coverage with drug benefits during the entire study period. They defined outcomes in the study as either 30% decrease or 30% improvement in the patients' eGFR test results from baseline to the last available result.
During the study's span, 2,690 patients received ULT and 10,061 patients did not. Serum urate level goals were met in 42% of the patients who were on ULT. Of those achieving this goal, 17.1% also showed a 30% improvement in their eGRF, compared to only 10.4% of those patients who did not meet the serum urate goal.
As for the influence of CKD stage at the onset of ULT, 7.1 of Stage 2 patients, 19.9% of Stage 3 patients, and 30% of Stage 4 patients all met the goal of 30% improvement in eGRF. Stage 3 patients had the most pronounced effect from ULT on their kidney function.
The study's findings suggest that CKD patients who achieve the ACR serum urate goal of <6mg/dl have higher rates of eGFR improvement, a key measure for kidney function and prevention of life-threatening kidney failure.
"This study suggests that patients with CKD should be tested for uric acid independent of whether they have gout or not. In patients with significantly elevated serum uric acid and moderate kidney failure, the addition of urate lowering therapy may help stabilize or improve kidney function," said Dr. Levy.