Results There was no significant difference in LFI values between stages S1 and S2 and between stages S0 and S1 (P>0.05); however, a significant difference was observed in LFI values between S0 and S1, S2, S3, or S4 (t=2.32, 3.92, 6.35, 11.58), between S1 and S0, S2, S3, or S4 (t=2.32, 1.59, 4.15, 9.44), between S2 and S0, S1, S3, or S4 (t=3.92, 1.59, -3.31, -9.86), between S3 and S0, S1, S2, or S4 (t=6.35, 4.15, 3.31, 6.28), and between S4 and S0, S1, S2, or S4 (t=11.58, 9.44, 9.86, 6.28) (P<0.05 for all). A significant difference was also observed in Lt-Kt values between S0 and S1, S2, S3, or S4 (t=-1.81, -4.51, -5.98, -9.58), between S1 and S0, S2, S3, or S4 (t=1.81, -2.37, -3.94, -7.60), between S2 and S0, S1, S3, or S4 (t=4.51, 2.37, -2.12, -6.69), between S3 and S0, S1, S2, or S4 (t=5.98, 3.94, 2.12, -4.37), and between S4 and S0, S1, S3, or S4 (t=9.58, 7.60, 6.69, 4.37) (P<0.05 for all). The areas under the ROCs (AUROCs) of LFI for S1-S4 were 0.953, 0.924, 0.916, and 0.983, respectively, and the AUROCs of Lt-Kt for S1-S4 were 0.979, 0.967, 0.902, and 0.949, respectively. The AUROCs of LFI combined with Lt-Kt for S1-S4 were 0.988, 0.974, 0.918, and 0.966, respectively.