RRM2 and acute kidney injury: Then, we evaluated the diagnostic efficiency of these key gene signatures, and ROC analysis revealed that these key gene signatures had certain predictive value in COVID-19 (RRM2 (AUC: 0.953), EGF (AUC: 0.853), TMEM252 (AUC: 0.676), RARRES1 (AUC: 0.757), COL6A3 (AUC: 0.747), CUBN (AUC: 0.709), Fig. 4C) and AKI (RRM2 (AUC: 0.849), EGF (AUC: 0.839), TMEM252 (AUC: 0.788), RARRES1 (AUC: 0.796), COL6A3 (AUC: 0.775), CUBN (AUC: 0.887), Fig. 4D), respectively.