Statistical analysis

Data are presented as the mean ± SD, as indicated in each graph. The Student’s t-test was used to evaluate the differences between means for normally distributed immunoblotting data. The significance of the ELISA results was analyzed using the Mann-Whitney test. All p-values were two-tailed, and p-values less than 0.05 were considered statistically significant. Receiver operating characteristic (ROC) curves were generated based on logistic regression from the ELISA data. Statistical analysis was performed using SPSS 22.0 for Windows (SPSS, Inc., Chicago, IL, USA). The area under ROC curve (AUC) calculation provided a convenient number. AUC < 0.5 indicated that the test showed no difference between the two groups, while 0.5 < AUC < 1.0 indicated that the test yielded perfect differentiation between groups at *p < 0.05, **p < 0.01, ***p < 0.001, or ****p < 0.0001.