title: Uric acid is not associated with decline in renal function or time to renal replacement therapy initiation in a referred cohort of patients with Stage III, IV and V chronic kidney disease.
abstract: BACKGROUND
  Although many studies have suggested an association between higher uric acid (UA) and both development of chronic kidney disease (CKD) and faster decline in renal function in Stage I and II CKD, it is not clear whether this effect is consistent throughout higher CKD stages. The aim of this study was to investigate the association between baseline UA and renal outcomes in patients with established CKD (Stages III-V).
  
  
  METHODS
  We analysed data in the Swedish Renal Registry-Chronic Kidney Disease (SRR-CKD), which is a nationwide registry of referred CKD patients. Patients with a visit between January 1(st), 2005 and December 31(st), 2011 were followed until initiation of renal replacement therapy (RRT), death, referral to primary care or end of follow-up. Decline in renal function was assessed with a linear mixed model using all estimated glomerular filtration rate (eGFR) assessments recorded during median 28 months of follow-up, adjusting for important confounders such as demographic factors, primary renal disease, age, sex, relevant medication, diet, blood pressure and body mass index.
  
  
  RESULTS
  There were 2466 patients with a baseline UA measurement {mean [standard deviation (SD)] of 7.81 [1.98] mg/dL}. The mean decline in renal function was -1.48 (95% CI -1.65; -1.31) mL/min/1.73 m(2) per year. The overall adjusted change in decline in renal function per unit increase in baseline UA was 0.08 (95% CI -0.01; 0.17) mL/min/1.73 m(2) per year indicating no association between higher UA levels and decline in renal function. In Stage III, IV and V CKD patients, the mean decline in renal function was -1.52 (95% CI -1.96; -1.08), -1.52 (95% CI -1.72; -1.32) and -1.19 (95% CI -1.75; -0.64) mL/min/1.73 m(2) per year, respectively. The adjusted change in the decline in renal function per unit increase in baseline UA was -0.09 (95% CI -0.30; 0.13) in Stage III CKD, 0.16 (95% CI 0.04; 0.28) in Stage IV CKD and 0.18 (95% CI -0.09; 0.45) in Stage V CKD. The overall adjusted hazard ratio for start of RRT was 0.97 (95% CI 0.93-1.02). For Stage III, IV and V CKD, it was 0.99 (95% CI 0.73-1.34), 0.97 (95% CI 0.91-1.03) and 0.99 (95% CI 0.91-1.07), respectively.
  
  
  CONCLUSIONS
  UA is not associated with the rate of decline in renal function or time to start of RRT in Stage III, IV and/or V CKD patients.
authors.affiliation: The Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Hakan
authors.initials: H
authors.lastname: Nacak
authors.affiliation: The Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Merel
authors.initials: M
authors.lastname: van Diepen
authors.affiliation: Renal Medicine, CLINTEC, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Abdul R
authors.initials: AR
authors.lastname: Qureshi
authors.affiliation: Renal Medicine, CLINTEC, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Carrero
authors.affiliation: The Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Theo
authors.initials: T
authors.lastname: Stijnen
authors.affiliation: The Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Friedo W
authors.initials: FW
authors.lastname: Dekker
authors.affiliation: Renal Medicine, CLINTEC, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Marie
authors.initials: M
authors.lastname: Evans
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood*; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D033461:Hyperuricemia / Q000097:blood* / Q000175:diagnosis / Q000517:prevention & control / Q000628:therapy; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012017:Referral and Consultation; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000145:classification / Q000628:therapy; D017582:Renal Replacement Therapy; D014527:Uric Acid / Q000097:blood*
chemical_list: D015415:Biomarkers; D014527:Uric Acid
keywords: (progression of) CKD; hyperuricaemia