Kinetics of hepatitis C virus RNA load during pegylated interferon alpha-2a and ribavirin treatment in naïve genotype 1 patients

Table 2 Diagnostic values and viral drop threshold for Week 2, 4, 8 and 12 analyses.

Week	Viral Drop Threshold (log₁₀copies/ml)	Area Under ROC Curve (95% CI)	Sensitivity (95% CI)	Specificity (95% CI)	PPV (95% CI)	NPV (95% CI)
2	1.39	0.93 (0.72;0.99)	91 (59;99)	89 (52;98)	91 (59;99)	89 (57;98)
4	2.81	0.89 (0.67;0.98)	100 (71,100)	67 (30;92)	79 (52;92)	100 (61;100)
8	2.81	0.79 (0.55;0.94)	73 (39;94)	78 (40;97)	80 (45;94)	70 (35;85)
12	2.81	0.81 (0.57;0.95)	73 (39;94)	89 (52;98)	89 (52;98)	73 (39:94)

The ROC curve method was used to determine the best cut-off that corresponds to the higher rate of sensitivity and specificity of predictions at week 2, week 4, week 8, and week 12. The accuracy of the test is measured by the area under the ROC curve. This area measures the discrimination, that is, the ability of the test to correctly classify patients with SVR and those without SVR. The analysis shows that the best results are obtained for week 2 viral drop, with a viral drop threshold of 1.39, an area under curve of 0.93, and a sensitivity, a specificity, a PPV, and a NPV rate of respectively 91%, 89%, 91%, and 89%. (P was non-significant for all areas under ROC curves comparisons.)