IL6 and COVID-19: For diagnosis of the severe and critical COVID-19, the area under ROC curve of IL-6 was the largest among all cytokines; the preoperative IL-6 concentration of 9.16 pg/ml was the optimal cutoff value (sensitivity = 70 (56.8–81.1)%, specificity = 82.8 (73.2–90.0)%), the positive predictive values = 73.3(60.3–84.5)%, the negative predictive values = 80.0(70.2–87.7)% (Figure 6 and Supplementary Table 6).