The study validated the Renal Activity Index for Lupus as a reliable biomarker panel for identifying active lupus nephritis and tracking treatment response over time.
For this purpose, researchers analyzed urine samples from adults enrolled in two major clinical trials: TULIP-LN (patients with biopsy-confirmed active Class III and IV lupus nephritis) and TULIP-1 (patients with active non-renal SLE). Six key urinary biomarkers—NGAL, KIM-1, MCP-1, adiponectin, hemopexin, and ceruloplasmin—were measured to calculate RAIL scores at baseline, and again at 12 and 24 weeks in the lupus nephritis group.
The study revealed the following key results:
- Median RAIL scores were significantly higher in patients with active lupus nephritis than in those with non-renal systemic lupus erythematosus [5.59 vs. 3.57].
- Levels of all six urinary biomarkers (NGAL, KIM-1, MCP-1, adiponectin, hemopexin, and ceruloplasmin) were also markedly elevated in the lupus nephritis group, underscoring RAIL’s diagnostic accuracy in distinguishing renal from non-renal lupus activity.
- RAIL scores declined over time in patients who responded to therapy, indicating its ability to reflect treatment-related improvements.
- By Week 12, 25 patients achieved complete renal response (CRR), 39 achieved partial renal response (PRR), and 41 met the criterion of a 50% reduction in urine protein-to-creatinine ratio (UPCR50).
- By Week 24, these numbers increased to 31 (CRR), 54 (PRR), and 63 (UPCR50), respectively, showing progressive therapeutic gains.
- Responders showed a greater drop in RAIL scores than non-responders at both follow-up intervals.
- For those achieving CRR, the median RAIL score fell by –1.3 at Week 12 and –2.30 at Week 24, compared with smaller reductions among non-responders.
- These differences were statistically significant, confirming RAIL’s value as a dynamic biomarker for tracking disease activity and treatment response in lupus nephritis.
The findings demonstrated that RAIL, a biomarker-based urine test, can effectively distinguish between active lupus kidney inflammation and non-renal lupus disease. Moreover, the study showed that RAIL scores closely mirror treatment response, decreasing significantly in patients who showed clinical improvement.
The authors emphasized that current methods for assessing lupus nephritis activity, such as kidney biopsies and proteinuria measurements, have limitations in capturing real-time changes in renal inflammation. RAIL, as a non-invasive urine-based tool, offers a promising alternative for both diagnosis and disease monitoring.
"These findings pave the way for more precise, non-invasive disease monitoring strategies in adults with systemic lupus erythematosus, potentially improving individualized patient care and therapeutic decision-making," the authors concluded.
Reference:
Brunner, H. I., Cody, E. M., Devarajan, P., Huang, B., Chen, C., Sinibaldi, D., Ramaswamy, M., Knagenhjelm, J., Jones, F., Brohawn, P. Z., Tummala, R., Lindholm, C., & White, W. I. The Renal Activity Index for Lupus Identifies Active Renal Disease and Treatment Response in Adult Patients With Systemic Lupus Erythematosus and Lupus Nephritis. Arthritis Care & Research. https://doi.org/10.1002/acr.25684
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