Levels of Proteinuria and Renal Pathology in Systemic Lupus Erythematosus Patients

Abstract

According to the current guidelines, renal biopsies are performed in systemic lupus erythematosus (SLE) patients for proteinuria of 0.5 g/24 h or higher. Renal pathology may be present in patients with lower-level proteinuria (<0.5 g/24 h). We aimed to review the renal histopathology in SLE patients, with lower levels of proteinuria. In this retrospective study, we retrieved SLE patients' data, including 24-h urinary protein excretion and renal histopathology results. We compared various parameters in different lupus nephritis (LN) classes and in different levels of proteinuria (urinary protein <0.5 g, 0.5 to <1 g, and ≥1 g per 24 h). Out of 476 patients, 274 (57.6%) had proteinuria of <0.5 g, 44 (9.2%) had 0.5 to <1 g, and 158 (33.2%) had ≥1 g per 24 h. SLE patients with proteinuria of <0.5 g/24 h were found to have LN, including the proliferative classes. Of the 299 LN cases confirmed by a renal biopsy, low-level proteinuria (<0.5 g) was found in 39.8% of all LN patients, in 50% of patients with Class III LN, 33.3% of those with Class IV LN, 31.4% of those with Class V LN, and 41.4% of those with other LN classes (II/V, III/V, and IV/V). Overall, 35.9% (87/242) of patients with the proliferative LN classes (III, IV, V, II/V, III/V and IV/V) had low-level proteinuria of <0.5 g/24 h. SLE patients with low-level proteinuria had significant renal pathology. Our study suggests there is a need to perform renal biopsies at lower levels of proteinuria.