Associations of serum urea, creatinine and uric acid with clinical and laboratory features in patients with systemic lupus erythematosus

The aim of this study is to investigate the associations of serum urea, creatinine and uric acid levels with clinical and laboratory characteristics, independent of lupus renal involvement in SLE patients. A total of 191 SLE patients were included in the present study. Some clinical and laboratory characteristics of the patients were obtained by medical record review. The results showed that serum urea, creatinine and uric acid levels seemed to be associated with several clinical and laboratory characteristics of SLE. However, multivariate logistical regression analysis indicated that increasing serum urea levels were positively associated with disease duration and thrombocytopenia, but negatively with arthritis and skin rash. Compared with quartile 1 of urea, the ORs of quartile 2, quartile 3 and quartile 4 were, respectively, 1.008 (0.997–1.015, P = 0.189), 1.010 (1.001–1.019, P = 0.038) and 1.014 (1.004–1.024, P = 0.008) with increasing disease duration; 1.912 (0.516–7.088, P = 0.332), 10.126 (2.771–36.997, P = 0.000) and 5.583 (1.285–24.266, P = 0.022) with thrombocytopenia; 0.864 (0.331–2.254, P = 0.765), 0.516 (0.18–1.475, P = 0.217) and 0.162 (0.047–0.557, P = 0.004) with arthritis; and 0.342 (0.135–0.868, P = 0.024), 0.215 (0.074–0.622, P = 0.005) and 0.332 (0.097–1.13, P = 0.078) with skin rash. Increasing serum creatinine levels were positively associated with sex, disease duration and SLEDAI, but negatively with skin rash. Compared with quartile 1 of creatinine, the ORs of quartile 2, quartile 3 and quartile 4 were, respectively, 2.993 (0.282–31.74, P = 0.363), 7.937 (0.861–73.18, P = 0.068) and 13.411 (1.32–36.246, P = 0.028) with male, 1.011 (1.002–1.02, P = 0.017), 1.002 (0.991–1.013, P = 0.684) and 1.018 (1.008–1.028, P = 0.001) with increasing disease duration; 1.112 (1.006–1.228, P = 0.038), 1.065 (0.959–1.183, P = 0.239) and 1.140 (1.022–1.272, P = 0.019) with increasing SLEDAI; and 0.303 (0.119–0.771, P = 0.012), 0.282 (0.104–0.76, P = 0.012) and 0.174 (0.052–0.584, P = 0.005) with skin rash. Increasing serum uric acid levels were only positively associated with erythrocytopenia. Compared with quartile 1 of uric acid, the ORs of quartile 2, quartile 3 and quartile 4 were, respectively, 0.910 (0.37–2.239, P = 0.837), 2.147 (0.901–5.116, P = 0.085) and 3.079 (1.211–7.828, P = 0.018) with erythrocytopenia. The present study demonstrated that, except for reflecting renal function, serum urea, creatinine and uric acid exert separate clinical significances in SLE.