Background Understanding the relationship between hyperuricemia and renal disease may help improve renal outcomes in patients with gout.
Objectives To evaluate the association between SrUA levels and risk of renal disease in patients with gout using electronic health records (EHR) data.
Methods Data for this retrospective analysis were derived from de-identified EHR data in the Humedica database from 2010 through 2013. Patients were adults (≥18 years) with ≥2 ICD-9-CM diagnoses for gout ≥30 days apart (the first ICD-9 diagnosis was the index date), with ≥1 SrUA assessments on or after the index date, and ≥6 months pre- and ≥12 months post-index activity. Renal disease was identified by ICD-9 codes, and included a variety of conditions including acute renal failure, hypertensive chronic kidney disease, renovascular hypertension, nephritis, nephritic syndrome, and nephrosis. Patients were stratified by four defined, clinically relevant SrUA ranges based on their SrUA assessment closest to the renal diagnosis, or their last assessment during the study period for those without a renal diagnosis: Group 1, 0.01-4.0mg/dL (n=5784); Group 2, 4.1-6.0mg/dL (n=9939); Group 3, 6.1-8.0mg/dL (n=12,572); and Group 4, ≥8.1mg/dL (n=9514). Survival curves for each group were generated using Kaplan-Meier (KM) estimates and compared using the log-rank test; patients with any ICD-9 diagnosis of renal disease during the 6-month pre-index period were excluded. A Cox proportional hazards time to renal event analysis was also performed to explore additional potential risk factors among demographic and clinical variables.
Results Gout patients were mostly male (72.4%), white (80.9%), with a mean ± SD age of 62.8±13.3 years and a mean ± SD Charlson Comorbidity Index (CCI) of 0.69±1.14. Overall, 14.9% of patients were diagnosed with renal disease during the 12-month post-index period, with 3.4% diagnosed concurrently at the index date. KM curves (Figure) showed significant differences in number of patients diagnosed with renal disease across the groups during the post-index period (P<0.0001). In particular, pairwise comparison showed that renal disease was diagnosed in a significantly higher proportion of patients in Group 4 (>8.1mg/dL), 21.7%, relative to each of the other groups (all P<0.0001) (Figure). Group 1 was significantly greater relative to Group 2, 13.6% vs 11.7% (P<0.001), but was similar to Group 3 (12.7%); Group 3 was also significantly greater than Group 2 (P<0.05). Median time from first SrUA assessment to renal disease diagnosis was shortest in Group 4, 20 days, followed by Group 3, 27 days; the longest median time to renal disease diagnosis, 38 days, was in Group 2. Gender was the only potential risk factor not significant in the model; the largest Hazard Ratios were associated with race (African American vs Caucasian, 1.64) and CCI score (1.34 per unit increase).
Conclusions High SrUA appeared to be associated with increased risk of renal disease, and very low SrUA may also increase the risk. Further evaluation of the relationship and mechanisms underlying SrUA and renal disease is warranted.
Disclosure of Interest M. Essex Shareholder of: Pfizer Inc, Employee of: Pfizer Inc, M. Hopps Employee of: Pfizer Inc, M. Udall Shareholder of: Pfizer Inc, Employee of: Pfizer Inc, C. Fu Consultant for: Pfizer Inc, E. Bienen Consultant for: Pfizer Inc, J. Mardekian Shareholder of: Pfizer Inc, Employee of: Pfizer Inc, G. Makinson Shareholder of: Pfizer Inc, Employee of: Pfizer Inc