Development of a Detection Method for Soluble Urokinase‐Type Plasminogen Activator Receptor and Its Application in Predicting Prognosis of Severe COVID‐19

ABSTRACT

Identifying sensitive and specific blood biomarkers for early warning of severe COVID‐19 remains a critical clinical need. Based on previous findings of elevated cytokines in bronchoalveolar lavage fluid and blood, we developed a novel luciferase immunosorbent assay (LISA) that selectively quantifies biologically active full‐length suPAR and can eliminate interference from inactive fragments measured by conventional ELISA. Compared with conventional ELISA, LISA showed a lower detection limit (5.08 vs. 45.72 pg/mL) and a wider linear range (45.72–100,000.00 vs. 1234.46–11,111.11 pg/mL). In adult COVID‐19 patients, suPAR levels were significantly elevated in severe cases ( p < 0.001) and correlated positively with NLR and SII ( p = 0.003 for each), and with IL‐6 ( p  < 0.001), but negatively with lymphocyte count ( p  = 0.004). suPAR outperformed conventional inflammatory markers in predicting severe disease (AUC = 0.785) and adverse outcomes (AUC = 0.912), supporting its role as an independent predictor. In paediatric COVID‐19 patients, suPAR remained superior to other single peripheral blood biomarkers for severity prediction, despite weaker correlations with inflammatory indices. This study establishes a reliable method for quantifying functionally intact suPAR and demonstrates its age‐dependent predictive value, highlighting its potential for individualized risk stratification in COVID‐19 patients.