High plasma oxalate levels may increase the risk for chronic kidney disease (CKD) progression and incident CKD as well as the likelihood of sudden cardiac death among patients on dialysis, according to the findings of separate studies presented at Kidney Week 2021.

Among patients with an estimated glomerular filtration rate (eGFR, in mL/min/1.73 m2) of 45 or higher, those in the third and fourth quartiles of plasma oxalate levels had a significant 2.1- and 2.2-fold increased risk for CKD progression, respectively, compared with those in the first quartile, Maria Clarissa Tio, MD, of Brigham and Women’s Hospital in Boston, Massachusetts, and colleagues reported in a poster presentation.

The study included 1800 randomly selected participants in the Chronic Renal Insufficiency Study (CRIC), which enrolled individuals with CKD aged 21 to 74 years. Dr Tio’s team defined CKD progression as a 50% or greater decline in eGFR or development of end-stage kidney disease. They adjusted results for demographic factors, medications, comorbidities, and laboratory values that included hemoglobin, serum albumin, urine protein-to-creatinine ratio.


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Among participants with an eGFR of 45 or higher, each doubling of plasma oxalate values was significantly associated with a 34% increased risk for CKD progression and 28% increased risk for death in a fully adjusted model. In patients with an eGFR less than 45, each doubling of plasma oxalate levels was significantly associated with an 11% decreased risk of CKD progression.

In a separate longitudinal, retrospective, observational cohort study, Marja Puurunen, MD, PhD, of Synlogic in Cambridge, Massachusetts, and colleagues found a significant association between baseline urinary oxalate and development of incident CKD after adjusting for baseline urine calcium and citrate concentrations, sex, age, race, body mass index, and other potential confounders.

The study included 426,896 patients aged 18 years or older with no CKD at baseline and who had at least a single 24-hour urine collection and were eligible for analysis of incident CKD. Compared with patients who had urinary oxalate levels less than 20 mg/d, those with levels of 20-29 mg/d had significant 1.2-fold increased odds of incident CKD. Patients with levels of 80 mg/d or higher had 1.7% increased odds.

“These data strongly supporting findings from smaller previous studies that higher urine oxalate may contribute to the risk of developing CKD,” the authors concluded in a poster presentation.

In a third poster presentation, Anja Christine Pfau, MD, of Charite Universitatsmedizin Berlin in Berlin, Germany, and colleagues reported on a study demonstrating that high oxalate levels increased the risk for cardiovascular events and sudden cardiac death (SCD) in a cohort of patients receiving dialysis. In their study of 1108 patients, those in the highest oxalate quartile had a significant 40% increased risk for cardiovascular events (a composite of cardiac death, nonfatal myocardial infarction, and fatal or nonfatal stroke) and 62% increased risk for SCD compared with those in the lowest quartile, in adjust analyses.

Of the 548 patients who died during follow-up, 139 (25.4%) died from SCD.

“Elevated oxalate concentrations are a novel risk factor for cardiovascular events and sudden cardiac death in dialysis patients,” the authors concluded.

References

Tio MC, Srivastava A, Curhan GC, et al. Plasma oxalate and risk of adverse outcomes in CKD. Presented at: Kidney Week 2021, November 2-7, 2021. Abstract PO2251.

Puurunen M, Curhan GC, Behling M, et al. Relationship between 24-hour urinary oxalate and incident CKD among patients with and without underlying gastrointestinal disease. Presented at: Kidney Week 2021, November 2-7, 2021. Abstract PO2252.

Pfau AC, Ermer T, Coca SG, et al. High oxalate concentrations increase risk for sudden cardiac death in dialysis patients. Presented at: Kidney Week 2021, November 2-7, 2021. Abstract PO0604.