Factors associated with clinically significant nephritis in systemic lupus erythematosus patients who present with glomerular hematuria: a cross-sectional study.

EULAR recommends kidney biopsy in systemic lupus erythematosus (SLE) patients with glomerular hematuria, whereas both ACR and KDIGO require the presence of proteinuria and/or impaired kidney function. We explored the value of hematuria for the diagnosis of new-onset lupus nephritis (LN). Cross-sectional study of SLE patients who underwent diagnostic kidney biopsy in two independent centers. Clinically significant LN was defined as ISN/RPS class III, IV, V, or mixed III/IV + V. Presentation patterns were categorized by glomerular hematuria, proteinuria, and impaired kidney function. Among patients with glomerular hematuria, regression models identified factors associated with clinically significant LN, and a nomogram was constructed. Of 227 biopsies, 181 (79.7%) showed clinically significant LN. Isolated glomerular hematuria was evident in 11 patients, of whom 9 revealed non-LN pathology; the two LN cases (class II and III) both demonstrated concurrent SLE serologic activity. Among patients with glomerular hematuria (n = 137), independent factors associated with clinically significant LN included anti-dsDNA positivity (OR 12.00, 95% CI 3.36-51.40), higher non-renal SLEDAI score (OR 1.20 per point, 95% CI 1.02-1.46), higher proteinuria (OR 3.77 per 1 g/d, 95% CI 2.00-9.03), and younger age (OR 0.96 per year, 95% CI 0.91-1.00). The combined presence of these factors yielded a predicted probability of 97% (95% CI 90-99%) of clinically significant LN, whereas their absence was associated with a probability of only 6% (95% CI 1-23%). When considering the need for kidney biopsy in patients with lupus, hematuria should be evaluated in the context of overall disease activity; extra-renal and serologic activity substantially increase the likelihood of clinically significant LN.