Abstract
Psoriasis diagnosis and severity assessment rely on subjective skin evaluations. Elafin is a promising biomarker, yet no high-throughput clinical assay exists. A chemiluminescence immunoassay (CLIA) reagent kit for plasma Elafin has been developed and validated using automated analyzers to enable rapid diagnosis, objective severity stratification, and longitudinal monitoring. Analytical performance is rigorously assessed, including the limit of blank (LoB) (0.069 ng mL(-1)), limit of detection (LoD) (0.099 ng mL(-1)), limit of quantification (LoQ) (0.8 ng mL(-1)), linearity (0.8-200 ng mL(-1)), precision, recovery, reproducibility, and interference resistance. Plasma Elafin is quantified in 731 participants from five hospitals: 112 healthy controls, 466 psoriasis patients (mild = 164, moderate = 158, severe = 144), and 153 disease controls. The assay achieves 89% diagnostic accuracy with an area under the receiver operating characteristic curve (AUC) of 0.94 for psoriasis. It effectively distinguishes disease severity (AUC 0.68 mild vs moderate; 0.77 moderate vs severe), and Elafin levels correlated with treatment duration in moderate (R = 0.51) and severe (R = 0.41) cases. This CLIA reagent kit demonstrates excellent analytical and clinical performance, supporting automated, high-throughput Elafin detection as a reliable tool for diagnosing and managing moderate-to-severe psoriasis.