Abstract
OBJECTIVE: We evaluated the ability of the Renal Activity Index for Lupus (RAIL) to discriminate active lupus nephritis (LN) in adult patients with active systemic lupus erythematosus (SLE) and differentiate LN treatment response. METHODS: Urine samples from adults with biopsy-proven active class III and IV LN from TULIP-LN (active LN group; ClinicalTrials.gov identifier: NCT02547922) and adults with active, nonrenal SLE from TULIP-1 (active SLE group; ClinicalTrials.gov identifier: NCT02446912) were used, and RAIL biomarkers (neutrophil gelatinase-associated lipocalin, kidney injury molecule 1, monocyte chemotactic protein 1, adiponectin, hemopexin, and ceruloplasmin) were measured in the urine at baseline for both studies and at weeks 12 and 24 for TULIP-LN only. The groups were compared at baseline, and changes in RAIL scores from baseline in the active LN group were compared between nonresponders and responders over time, ie, those with complete renal response (CRR), partial renal response (PRR), and urine protein-creatine ratio decrease ≥50% (UPCR50). RESULTS: At baseline, median (interquartile range [IQR]) concentrations of RAIL biomarkers were significantly higher (P ≤ 0.02) in the active LN group (n = 128) versus the SLE control group (n = 48), as were RAIL scores (5.59 [IQR 4.31-6.47] vs 3.57 [IQR 2.78-4.47]; P < 0.001). At weeks 12 and 24, there were 25 and 31 patients with CRR, 39 and 54 patients with PRR, and 41 and 63 patients with UPCR50, respectively. Changes in RAIL scores from baseline to weeks 12 and 24 significantly differed between nonresponders and responders (PRR, CRR, UPCR50: all P < 0.0006), with lower scores in responders. For CRR versus non-response, median [IQR] RAIL scores decreased by -1.3 (-3.64 to -0.21) versus -0.39 at week 12, and -2.30 (-3.63 to -1.03) versus -0.88 (-2.20 to 0.33) at week 24, respectively. CONCLUSIONS: The RAIL identifies active LN and longitudinally differentiates treatment response in adults with LN.