Calibrator 25 is a lyophilized blend of CA1, Complement factor D, CRP, Cystatin C, Factor VII, NGAL/LCN2, and sTfR-1. It is intended for use as an assay calibrator for MSD U-PLEX human assays that measure any of the included proteins. The utility of this product has not been evaluated in other applications. Individual analyte concentrations are provided in the lot-specific certificates of analysis. CA1 was expressed in E. coli; Complement factor D, NGAL/LCN2 and sTfR-1 were expressed in a mouse cell line; CRP was expressed in mammalian cell line; and Cystatin C and Factor VII were expressed in a human cell line. Instructions on using Calibrator 25 are provided in U-PLEX Biomarker Group 3 Human Product Inserts.