Successful Urine Multiplex Bead Assay to Measure Lupus Nephritis Activity

Area of Science:

• Nephrology
• Immunology
• Biomarker Discovery

Background:

• Lupus nephritis (LN) diagnosis and therapy monitoring are challenged by a lack of effective laboratory tests.
• Previously identified 6 urinary biomarkers (NGAL, KIM-1, MCP-1, adiponectin, hemopexin, ceruloplasmin) show high sensitivity and specificity for active LN.
• The Renal Activity Score for Lupus (RAIL) was developed using these biomarkers measured by ELISA.

Purpose of the Study:

• To evaluate the performance of the RAIL score using urinary biomarkers measured by a bead multiplex method (LUMINEX) compared to ELISA.
• To determine if the multiplex bead method is a viable and comparable alternative for clinical utility.

Main Methods:

• Assayed 341 urine samples from 46 patients with or without LN using both ELISA and LUMINEX multiplex assays.
• Assessed agreement between biomarker quantities and RAIL scores using correlation coefficients, Bland-Altman analysis, and regression.
• Focused on NGAL, KIM-1, MCP-1, and adiponectin due to successful measurement by LUMINEX.

Main Results:

• LUMINEX successfully measured NGAL, KIM-1, MCP-1, and adiponectin, but not ceruloplasmin and hemopexin.
• Good agreement was observed for RAIL scores derived from these 4 biomarkers, regardless of assay method (ICC = 0.78).
• RAIL scores using 4 biomarkers strongly correlated with scores using all 6 biomarkers (ICC = 0.97).

Conclusions:

• The LUMINEX platform enables convenient, simultaneous measurement of 4 key RAIL biomarkers.
• RAIL scores based on these 4 biomarkers are sufficient for accurately assessing LN activity.
• This multiplex approach offers a promising enhancement for the clinical utility of RAIL in lupus nephritis management.