Uric acid is a strong independent predictor of renal dysfunction in patients with rheumatoid arthritis

Dimitrios Daoussis¹, Vasileios Panoulas¹, Tracey Toms¹, Holly John¹, Ioannis Antonopoulos¹, Peter Nightingale², Karen MJ Douglas¹, Rainer Klocke¹ and George D Kitas^1,3*

¹Department of Rheumatology, Dudley Group of Hospitals NHS Trust, Russells Hall Hospital, Pensnett Road, Dudley, West Midlands, DY1 2HQ, UK

²Wolfson Laboratory, Department of Medical Statistics, School of Medicine, University of Birmingham, Queen Elizabeth Medical Centre, Edgbaston, Birmingham, B15 2TH, UK

Arthritis Research & Therapy 2009, 11:R116 doi:10.1186/ar2775


Introduction


Arthritis Research Campaign Epidemiology Unit, University of Manchester, Oxford Road, Stopford Building, Manchester, M13 9PT, UKRecent evidence suggests that uric acid (UA), regardless of crystal deposition, may play a direct pathogenic role in renal disease. We have shown that UA is an independent predictor of hypertension and cardiovascular disease (CVD), and that CVD risk factors associate with renal dysfunction, in patients with rheumatoid arthritis (RA). In this study we investigated whether UA associates with renal dysfunction in patients with RA and whether such an association is independent or mediated through other comorbidities or risk factors for renal impairment.

Methods

Renal function was assessed in 350 consecutive RA patients by estimated glomerular filtration rate (GFR) using the six-variable Modification of Diet in Renal Disease equation. Risk factors for renal dysfunction were recorded or measured in all participants. Linear regression was used to test the independence of the association between GFR and UA.

Results

Univariable analysis revealed significant associations between GFR and age, systolic blood pressure, total cholesterol, triglycerides, RA duration and UA. UA had the most powerful association with renal dysfunction (r = -0.45, P < 0.001). A basic model was created, incorporating all of the above parameters along with body mass index and gender. UA ranked as the first correlate of GFR (P < 0.001) followed by age. Adjustments for the use of medications (diuretics, low-dose aspirin, cyclooxygenase II inhibitors and nonsteroidal anti-inflammatory drugs) and further adjustment for markers of inflammation and insulin resistance did not change the results.

Conclusions

UA is a strong correlate of renal dysfunction in RA patients. Further studies are needed to address the exact causes and clinical implications of this new finding. RA patients with elevated UA may require screening for renal dysfunction and appropriate management