Patient demographics and tumor characteristics
The cut-off value of AFP and PIVKA-II commonly used was 20ng/ml and 40mAU/ml respectively. Based on this critical value, patient demographics and tumor characteristics were outlined in Table 1. As shown in Table 1, we found that AFP had strong correlation with tumor size (measured by diameter) and differentiation (p<0.01). PIVKA-II was also related to tumor size.
AFP and PIVKA-II serum levels in experimental and control group
The median levels of AFP and PIVKA-II in HCC patients were 24.64 (IQR 4.38~528.82) and 334.08 (IQR 60.88~5095.10), while their concentrations of control group were 3.20 (IQR 1.90~9.60) and 22.17 (IQR 17.59~30.05) respectively. As shown in the Fig.1, the AFP and PIVKA-II levels were signiﬁcantly higher in the HCC group than that in the control group (Z was 7.428, 11.243 respectively, P all <0.01).
Comparison of AFP and PIVKA-II single and combined detection in HCC diagnosis
The ROC curve was plotted to compare diagnostic values of AFP and PIVKA-II detected singly or jointly in HCC and identify their cut-off values that would best distinguish patients with HCC from control group. As pictured in the Fig.2, the AUC of HCC diagnosis was 0.765 (95% CI, 0.713～0.8170) for AFP, and 0.901 (95% CI, 0.868～0.935) for PIVKA-II. The combination of AFP and PIVKA-II improved the diagnostic performance for HCC (AUC 0.917; 95% CI, 0.886～0.948). The diagnostic values of AFP and PIVKA-II combined detection or single assay of PIVKA-II were better than that of separate assay of AFP (Z was 5.927 and 4.51 respectively, P all <0.001). There was no significant difference of diagnostic accuracy between joint test of the two biomarkers and PIVKA-II detected singly (Z was 1.795, P = 0.0727). The optimal cut-off value of HCC diagnosis was 21.8ng/ml for AFP and 41.74mAU/ml for PIVKA-II. At the optimal cut-off value of AFP and PIVKA-II, sensitivity and specificity in diagnosis of HCC were reflected in Fig.2.
Correlations between AFP, PIVKA-II serum levels and tumor differentiation and size (measured by diameter) of HCC
The AFP, PIVKA-II concentration showed signiﬁcant differences in well/moderate/poor differentiation as well as tumor size of HCC. Generally, the serum levels of AFP and PIVKA-II were positively correlated with tumor differentiation and size, just as shown in Fig.3.
Predictive value of AFP and PIVKA-II for HCC vascular invasion
The median levels of AFP and PIVKA-II in HCC patients without vascular invasion were 15 (IQR 3.4~69) and 174.71 (IQR 46.76~1156.6), while their concentrations of patients with vascular invasion were 45 (IQR 6.37~1039.2) and 549.3 (IQR 65.13~7805.3) respectively. As shown in the Fig.4, the AFP and PIVKA-II level in HCC with or without vascular invasion was obviously different. High AFP and PIVKA-II expression was signiﬁcantly associated with the presence of vascular invasion (Z was 2.683, 2.463 respectively, P = 0.007 and 0.014). The AFP level >64.4ng/ml or PIVKA-II level >957.61mAU/ml was the independent predictor of vascular invasion.