Kidney Week

Abstract: SA-PO272

Plasma Oxalate as a Predictor of Kidney Function Decline in Primary Hyperoxaluria

Session Information

• Bone and Mineral Metabolism: Calcium, Magnesium, Kidney Stones
  November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Bone and Mineral Metabolism

• 402 Bone and Mineral Metabolism: Clinical

Authors

• Shah, Ronak Jagdeep, Mayo Clinic, Rochester, Minnesota, United States

Ronak Jagdeep Shah,

• Vaughan, Lisa E., Mayo Clinic, Rochester, Minnesota, United States

Lisa E. Vaughan,

• Enders, Felicity T., Mayo Clinic, Rochester, Minnesota, United States

Felicity T. Enders,

• Milliner, Dawn S., Mayo Clinic, Rochester, Minnesota, United States

Dawn S. Milliner,

• Lieske, John C., Mayo Clinic, Rochester, Minnesota, United States

John C. Lieske,

Background

This retrospective analysis investigated plasma oxalate (POx) as a potential predictor of end stage kidney disease (ESKD) among primary hyperoxaluria (PH) patients across varying stages of CKD.

Methods

PH patients with type 1, 2 and 3, age 2 or older, with estimated glomerular filtration rate (eGFR) and POx measures available during follow-up after PH diagnosis and prior to ESKD were identified in the RKSC PH Registry. Urinary oxalate (UOx) did not change across CKD stages 1-3, but POx increased with falling eGFR. Thus to maximize data for analysis of POx by eGFR stage, patients were further subdivided into CKD subgroups (stages 1, 2, 3a and 3b) such that a patient started in a given CKD stage subgroup on their first eGFR observed in that range, while also continuing to remain in any prior groups. ESKD was defined as an eGFR<15 ml/min per 1.73 m² or start of dialysis or renal transplantation. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) for risk of ESKD were estimated using the Cox proportional hazards model with a time-dependent covariate.

Results

There were 118 patients in the CKD1 group (9 ESKD events during follow-up); 135 in CKD 2 (29 events); 72 in CKD3a (34 events); and 45 patients in CKD 3b (31 events). During follow-up, POx Q4 was a significant predictor of ESKD compared to Q1 across CKD2 (HR 14.2, 95% CI 1.8-115), 3a (HR 13.7, 95% CI 3.0-62) and 3b stages (HR 5.2, 95% CI 1.1-25), P<0.05for all. Within each POx quartile, ESKD rate was higher for more severe CKD stages, and within each CKD stage, ESKD rate was higher in Q4 compared to Q1-Q3, respectively.

Conclusion

Among patients with PH, higher POx concentration was a risk factor for ESKD, particularly in advanced CKD stages.

ESKD rate per 100 patient years by CKD stage and POx quartile.

Funding

• NIDDK Support –