Background/Purpose:   To determine if urate lowering therapy (ULT) can improve Chronic Kidney Disease (CKD) function when patients achieve a serum uric acid (sUA) <6mg/dL (Goal). To determine if baseline CKD stage influences the benefits when attaining Goal with ULT.

Methods:   A retrospective cohort study was conducted from 1/1/2008 to 7/31/2014 within an integrated healthcare delivery system. A sUA > 7mg/dL was necessary for inclusion and the first occurrence sUA >7mg/dl was defined as the index date. In addition, patients were required to have an estimated Glomerular Filtration Rate (eGFR) in the 6 months preceding the index date, and at least one sUA and eGFR during follow-up, from 3 months to 12 months post index. Patients were required to be ULT naïve, ≥ 18 years of age, and have Chronic Kidney Disease Stages 2, 3 or 4 at index. Continuous health plan enrollment with a drug benefit during the entire study period was required. Exclusions included active treatment for cancer, dialysis or kidney transplant.  Outcomes were defined as either a 30% decrease or a 30% improvement in eGFR from baseline to the last available value.  Pairwise differences in proportion were compared using Chi-square test and 95% Confidence Interval (CI) were reported for the differences.

Results:   Of the 12, 751 patients meeting inclusion criteria; 2, 690 received ULT during the study period and 10,061 did not.  Goal sUA was achieved in 1,118 (42%) patients on ULT.   A 30% improvement in eGFR was seen in 17.1% achieving Goal versus 10.4% of patients who did not reach sUA goal (Difference = 6.7% (95% CI = 4.0%, 9.4%), p<0.001).  Pairwise comparison of CKD stages showed patients at or below Goal were more likely to have a 30% improvement in eGFR: in CKD 2:  7.1% v 3.3%, (Difference = 3.8% (95% CI = 0.7%, 7.0%), p=0.015) , in CKD3: 19.9% v 10.0%, (Difference = 9.9% (95% CI = 6.1%, 13.6%), p<0.001) and CKD 4:  30.0% v 22.2%, (Difference = 7.8% (95% CI = -1.1%, 16.8%), p=0.080).

Conclusion:   This study suggests that patients who achieve ACR Goal of sUA of <6mg/dl on ULT have higher rates of eGFR improvement (≥ 30% improvement).  This effect is seen across the CKD spectrum from Stage 2 through Stage 4 with the most pronounced effect in CKD 3 patients.