Background Hyperuricemia is particularly common in patients with chronic kidney disease (CKD). Its role, however, as a risk factor for renal outcomes of CKD is debated and those data in gout patients with CKD are rare.
Objectives This aim of study was to evaluate long-term effect of serum uric acid (SUA) level on progression of CKD in gout patients with uric acid lowering treatment.
Methods All patients who had a first visit for gout with CKD at Samsung Medical Center between 1995 and 2003, and follow-up until December 2012 or expired during follow-up period were included and retrospective analyzed. CKD was defined as an estimated glomerular filtration rate GFR) of <60 mL/min/1.73m2 via the Modification of Diet in Renal Disease Study equation more than 3 months according to the Kidney Disease Outcome Quality Initiative CKD classification. All serum creatinine and matched SUA taken during follow-up period were analyzed by using mixed effect model to determine the effect of SUA level on renal outcome.
Results One-hundred eleven gout patients with CKD were observed. The mean age of the patients at diagnosis of gout was 51.3 and mean follow-up duration was 13 years. Baseline estimated GFR and serum creatinine were 47.7 mL/min/1.73m2 and 1.62 mg/dL, respectively. Eight (7.2%) patients revealed CKD stage 4 and the rest of patients (92.8%) were CKD stage 3. Maintaining the SUA below 6 mg/dL showed protective effect on serum creatinine and estimated GFR compared with maintaining SUA more than 6 mg/dL (p <0.0001 and p =0.02, respectively). The elevation of SUA as a continuous variable was also related to poor renal outcome in gout patients with CKD (p <0.0001). This effect of SUA on progression of CKD was not changed after adjusting for duration of gout and age at baseline, time-dependent hypertension, diabetes mellitus, hyperlipidemia, obesity, intrinsic renal diseases, and obstructive renal diseases. In particular, for every 1 mg/dL increase of the SUA, serum creatinine revealed to be increased by 0.019 mg/dL in group with SUA more than 6 mg/dL. Hypertension, diabetes mellitus and intrinsic renal disease were independent risk factors for progression of CKD in gout patients (p <0.0001, p <0.0001 and p =0.014, respectively).
Conclusions Our long term follow-up data demonstrated the SUA level was independent risk factor for progression of CKD in gout patients with uric acid lowering treatment. Maintaining of SUA level below 6 mg/dL would be essential to protect renal function in gout patients with CKD.
Disclosure of Interest None declared