Value of Uric Acid as Early Predictor of Lupus Nephritis

Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disorder identified by the production of autoantibodies and immune complex deposition [1]. It presents with a variety of unpredictable flares of disease activity and irreversible organ damage [2]. Half or more (45%-85%) of patients with SLE will develop Lupus Nephritis (LN) over the course of their lifetime, which is a major concern [3,4]. Despite advanced immunosuppressive therapy, the 5-year survival rate of SLE patients with severe renal damage (11%-33%) is usually very low [5].

Hence, early prediction and diagnosis of LN are of great value. So far, renal biopsy remains to be the gold standard tool for diagnosis of LN [6] and assumes a vital role in its management and prognosis. However, renal biopsy can have various complications including hemorrhage and infection. Besides, some patients have contraindications for renal biopsy, which indicates the requirement for noninvasive markers for evaluating renal dysfunction and its grade [7].

• Elimination of serum uric acid (SUA), the circulating endproduct of purine metabolism, occurs via both renal and extrarenal (gastrointestinal tract) pathways [8]. Kang and colleagues [9] have reported that elevated serum uric acid may also be a risk factor for progression of renal disease, in spite of the fact that it is considered as one of the markers of renal dysfunction. Elevated serum uric acid itself can lead to kidney damage without the deposition of uric acid crystals as reported in different studies [10]. Other studies strongly suggest to consider the concept of asymptomaticity for chronic hyperuricemia and hence to check the normal level of serum uric acid levels [11].

Hyperuricemia can be observed in patients with diabetic nephropathy , IgA nephropathy , metabolic syndrome and cardiovascular diseases [12,13,14,15]. In addition, a noteworthy positive relationship was detected between serum level of uric acid and new onset lupus nephritis. Elevated sUA has been observed as an independent risk factor for the development of LN . The correlation between sUA and the degree of renal dysfunction in LN patients was previously analyzed but in a few studies as in Calich and colleagues study who reported an association between lupus nephritis and high serum UA . Therefore the aim of the current study was to evaluate serum uric acid level and detect if hyperuricemia can independently predict and affect prognosis of LN among SLE patients.