Abstract
Background Lupus nephritis (LN) is the most common severe manifestation of systemic lupus erythematosus (SLE) that can involve all kidney components. The International Society of Nephrology/Renal Pathology Society (ISN/RPS) 2003 lupus nephritis classification only focuses on glomerular involvement, although tubulointerstitial inflammation (TI) is a better predictor of renal failure. Objective To determine the association of non-albumin proteinuria (NAP) and severity of tubulointerstitial inflammation in lupus nephritis patients. Methods This cross-sectional study was carried out in the Department of Nephrology of Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh. A total of eighty (80) LN patients were enrolled in this study. Their urinary protein-to-creatinine ratio (uPCR), urinary albumin-to-creatinine ratio (uACR), renal biopsy, and relevant routine investigations were done accordingly. Urinary non-albumin proteinuria (uNAP) was measured by subtracting uACR from uPCR. Data were analyzed and compared by statistical tests. Results Among 80 lupus nephritis patients, 39 (48.8%) had no-to-mild tubulointerstitial inflammation (TI), whereas 41 (51.2%) had moderate-to-severe tubulointerstitial inflammation. Proliferative glomerulonephritis (GN) (class III/class IV) was observed in 48 patients (60%), while non-proliferative GN (class II/V) was present in 32 patients (40%). In the logistic regression analysis, non-albumin proteinuria (uNAP) was found to be associated with moderate-to-severe tubulointerstitial inflammation (OR: 3.166, 95% CI: 1.145-8.757, p=0.026). The calculated cutoff value for uNAP was 887, which corresponds to a sensitivity of 96.7% and specificity of 76.0% (p<0.001). Conclusion Non-albumin proteinuria is associated with the severity of tubulointerstitial inflammation in lupus nephritis. Therefore, assessing non-albumin proteinuria can offer clinically valuable insights into the management of lupus nephritis.