CAST and systemic lupus erythematosus: Even though the remaining four urine proteins, calpastatin, hemopexin, peroxiredoxin-6, and properdin, did not outperform anti-dsDNA in distinguishing active LN from inactive SLE patients, they were all significantly elevated in active LN when compared with inactive SLE patients, thus offering independent validation of the urinary biomarkers uncovered in this study, across multiple ethnic groups.