SAN DIEGO – Patients who achieve a serum uric acid level of less than 6 mg/dL based on current gout management guidelines demonstrated a 37% reduction in progression of renal disease, a large retrospective study showed.
"There are numerous studies showing that people with renal disease can develop hyperuricemia," Dr. Gerald D. Levy said during a press briefing at the annual meeting of the American College of Rheumatology. "Some of them will also develop gout. There are a few small studies showing that in humans, you can reverse hyperuricemia with urate lowering therapy and make an impact in renal disease. We wanted to see if this is true."
Dr. Levy of the division of rheumatology in the department of internal medicine at Kaiser Permanente Medical Group, Downey, Calif., was the lead investigators in a study of 111,992 Kaiser Permanente Southern California patients with a serum uric acid (SUA) level of 7 mg/dL or greater from Jan. 1, 2002, to Dec. 31, 2010. Patients with at least 12 months of health plan membership, including drug benefit prior to the index date, were studied. All patients had at least one SUA and glomerular filtration rate (GFR) level measurement in the 6-month period prior to the index date and at least one SUA and one GFR in the follow-up period following the index date. Primary outcome events were at least a 30% worsening of renal function, initiation of dialysis, having a GFR of less than 15 mL/min, and undergoing a kidney transplant.
Patients with a new diagnosis of cancer were excluded from the analysis, as were those with HIV, glomerulonephritis, and/or organ transplant other than a kidney transplant.
Dr. Levy reported results from 16,186 patients who were divided into three groups: those who were never treated with urate-lowering therapy (ULT; 11,192); those who were treated with ULT less than 80% of the time from the index date to the end of follow-up period (3,902); and those who were treated with ULT 80% of the time or more from the index date to the end of the follow-up period (1,092). Of the three treatment groups, those who were treated with ULT 80% of the time or more during the study tended to be older and have more comorbid conditions, compared with the other two groups. They also began their ULT therapy earlier.
Among all patients combined, factors significantly associated with renal disease progression included having diabetes (hazard ratio, 1.96), hypertension (HR, 1.50), heart failure (HR, 1.39), previous hospitalizations (HR, 1.33), and being female (HR, 1.49) and older (HR, 1.03). The researchers found that time on ULT was not significantly associated with a reduction in renal disease progression outcome events (HR, 1.27, among those on ULT less than 80% of the time during the study vs. HR, 1.08, among those on ULT 80% of the time or more during the study). However, patients who achieved an SUA level below 6 mg/dL – a treatment goal in the 2012 ACR guidelines for management of gout – demonstrated a 37% reduction in renal disease progression (HR, 0.63; P less than .0001).
Dr. Levy acknowledged certain limitations of the study, including its retrospective design and the fact that patients with stage 4 and 5 chronic kidney disease were not included. "This is an important area, because if we can delay the worsening of renal disease in these folks, perhaps we’re abetting dialysis, which is growing by leaps and bounds in this country," he said. "Each dialysis patient now costs about $80,000 per year to take care of. If we could push that back even for a few years it would have a tremendous impact."
Dr. Levy had no relevant financial conflicts to disclose.