Background Systemic Lupus Erythematosus (SLE) remains a diagnostic and therapeutic challenge, particularly lupus nephritis (LN). We previously described a composite score, the pediatric Renal Activity Index for Lupus (pRAIL), consisting of neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), monocyte chemotactic protein 1 (MCP-1), adiponectin, hemopexin and ceruloplasmin, where higher scores represent more active inflammation on biopsy. We hypothesized that when followed longitudinally during induction therapy, pRAIL significantly improves during induction therapy in complete responders, and aimed to assess the difference between complete and partial responders.
Methods Patients aged 23 and younger diagnosed with LN were recruited (IRB #2008-0635). Diagnosis was made according to ACR criteria for SLE, with renal biopsy confirmation of LN. Urine was collected at diagnosis and end of induction. Complete responders were defined by urine protein to creatinine ratio <0.5 mg/mg, absence of hematuria, and normal glomerular filtration rate.
Partial responders had decrease in proteinuria by 50% and GFR stable to improved from diagnosis. Response was also defined as improved activity index on follow up biopsy.
Descriptive analyses, ANOVA, paired and student t-tests were performed for analyses.
Results A total of 25 patients aged 23 or younger were recruited at the start of induction therapy. 15 of the patients were complete responders, 7 were partial responders. Table 1 shows the characteristics and pRAIL scores of the complete and partial responders pre and post therapy. Among the three non-responders, standardized and non-standardized pRAIL scores numerically increased during induction therapy. The mean±SD of pRAIL scores significantly decreased in complete responders by 1.07 ± 1.7 (p=0.03) and were unchanged in partial responders (0.07 ± 1.56, p= 0.91), as shown in figure 1.
Conclusions This study shows the pRAIL score (both absolute and standardized) distinguishes complete responders versus partial responders during induction therapy. Complete responders pRAIL score decrease by mean of 1 point, whereas partial responders had no change. Notably, standardized pRAIL scores yielded more pronounced differences during induction therapy among both partial and complete responders.
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