Development of a Novel Renal Activity Index of Lupus Nephritis in Children and Young Adults

Brunner, H. I.; Bennett, M. R.; Abulaban, K.; Klein-Gitelman, M. S.; O'Neil, K. M.; Tucker, L.; Ardoin, S. P.; Rouster-Stevens, K. A.; Onel, K. B.; Singer, N. G.; Anne Eberhard, B.; Jung, L. K.; Imundo, L.; Wright, T. B.; Witte, D.; Rovin, B. H.; Ying, J.; Devarajan, P.

Arthritis Care Res (Hoboken). 2015 Oct 17; 68(7):1003-11

Abstract

OBJECTIVE: Noninvasive estimation of the degree of inflammation seen on kidney biopsy with lupus nephritis (LN) remains difficult. The objective of this study was to develop a Renal Activity Index for Lupus (RAIL) that, based solely on laboratory measures, accurately reflects histologic LN activity. METHODS: We assayed traditional LN laboratory tests and 16 urine biomarkers (UBMs) in children (n = 47) at the time of kidney biopsy. Histologic LN activity was measured by the National Institutes of Health activity index (NIH-AI) and the tubulointerstitial activity index (TIAI). High LN-activity status (versus moderate/low) was defined as NIH-AI scores >10 (versus 5 (versus 92% accuracy and LN-activity (TIAI) status with >80% accuracy. RAIL accuracy was minimally influenced by concomitant LN damage. Accuracies between 71% and 85% were achieved without standardization of the UBMs. The strength of these UBMs to reflect LN-activity status was confirmed by principal component and linear discriminant analyses. CONCLUSION: The RAIL is a robust and highly accurate noninvasive measure of LN activity. The measurement properties of the RAIL, which reflect the degree of inflammatory changes as seen on kidney biopsy, will require independent validation.

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