Based on the presence of a statistically significant difference in plasma levels of HMGA2 protein between the bladder cancer patients group and the healthy group when applying Mann–Whitney test, a receiver operating characteristic (ROC) curve was constructed to study the sensitivity and specificity of plasma HMGA2 levels in discriminating the bladder cancer group and healthy group (shown in Fig. 4). The gene discussed is HMGA2; the disease is urinary bladder cancer.