Elevated Creatinine Clearance In Lupus Nephritis Patients With Normal Creatinine

Objectives: The present study aimed to observe the differences in creatinine clearance (Ccr) in systemic lupus erythematosus (SLE) patients with normal serum creatinine at different levels of urinary protein.Method: The present cross-sectional study included 177 SLE patients with normal serum creatinine from Qilu Hospital of Shandong University between January 2010 and April 2020. The following data were collected: blood urea nitrogen (BUN), serum creatinine (Cr), serum total protein, serum albumin, immunoglobulin (Ig) G, IgA, IgM, complement 3, complement 4, anti-ds-DNA antibody, routine urine test, urine protein/creatinine ratio (UPCR) (g/g), and the SLE disease activity index. The estimated Ccr was calculated according to the Cockcroft formula.Results: 123 patients were with positive urinary protein (Lupus Nephritis, LN group) and 54 patients were with negative urinary protein (Non-LN group). Compared with the Non-LN group, the LN group had higher BUN (5.76 +/- 3.22 vs. 4.78 +/- 1.58, P=0.007) and Cr (62.36 +/- 19.53 vs. 54.83 +/- 11.09, P=0.001). There was a strong correlation between the UPCR and the semi-quantitative determination of urine protein in LN patients (r=0.9583, P=0.0417). The serum creatinine levels were significantly higher in patients with urine protein 3+ (72.97 +/- 25.16) or massive proteinuria (62.32 +/- 19.66) than the other groups. Patients with urinary protein +/- exhibited a significantly elevated Ccr when compared to patients with urinary protein 3+ (130.6 +/- 44.15 vs. 110.5 +/- 33.50, P=0.02), and patients with UPCR<0.15 g/g had higher Ccr than other groups and showed significantly increased Ccr compared with patients with UPCRN/15 g/g (132.44 +/- 21.02 vs. 115.14 +/- 35.89, P=0.007).Conclusions: Early renal function impairment may be present in LN patients. The kidneys of LN patients with urinary protein +/- or UPCR<0.15 g/g are in a state of hyperfunction.