Does the standard proteinuria cut-off for renal biopsy in lupus nephritis as per the current guidelines hold good for Asian population? A single-centre study from South India.

Introduction: Current rheumatology and nephrology society guidelines in lupus nephritis do not recommend renal biopsy for proteinuria of less than 500 mg/24 h. This might lead to a significant delay in the early diagnosis of lupus nephritis.

Aim: The main aim of this study is to determine the nature of renal lesions in patients with low-grade proteinuria and to analyze the predictors for clinically significant lupus nephritis.

Methods: This was a single-center, retrospective study. All consecutive patients of lupus nephritis, with low-grade proteinuria (200 mg to 500 mg/24 h) undergoing renal biopsy were enrolled in this study. The renal biopsies were classified into significant lesions (Class III/IV/V) and non-significant lesions (Class I and II). Treatment naïve groups and treatment-modified groups were analyzed separately. Predictive factors for significant renal lesions were determined by univariate and multivariate analysis.

Results: We identified 183 patients of lupus with proteinuria between 200 and 500 mg / 24 h. Mean (SD) age was 30.2 (11.39) years with 167 (91.2%) of them being females. The mean (SD) baseline proteinuria was 351.03 (98.1) mg/24 h 85 patients (46.5%) had proliferative lupus nephritis where whereas 17 patients (9.3%) had membranous nephropathy. Crescents and fibrinoid necrosis were seen in 10 (5.46%) and 24 (13.11 %) patients respectively. Isolated proteinuria without any other sediments was seen in 95 patients (51.9%) of which 29 patients had proliferative lupus nephritis. Elevated Anti-double stranded DNA (anti-dsDNA), low C3, low C4 and the presence of urinary sediments were significantly associated with significant renal lesions in biopsy.

Conclusion: Significant renal lesions were seen in around half of the patients with low-grade proteinuria underscoring the importance of performing a renal biopsy in this set of patients. Low C3 and C4, urinary sediments, and elevated anti-dsDNA were predictors for significant renal lesions.