IGHG3 and lobular neoplasia: Urinary IGHG3 levels were significantly higher in patients with active LN (92.5 [24.5, 502.8] vs. 36.4 [3.3, 437.1] ng/mL, p < 0.001), and in patients with SLEDAI-2K > 6 (76.7 [24.5, 502.8] vs. 37.3 [3.3, 437.1] ng/mL, p < 0.001) than in those with SLEDAI-2K < 6.