Table 1.

Definitions for treatment response in interferon-based response-guided therapies

Term	Abbreviation	Definition
Sustained virological response	SVR	Undetectable HCV RNA 12–24 weeks after the end of therapy
Rapid virological response	RVR	Undetectable HCV RNA at week 4 of therapy
Early virological response	EVR	HCV RNA decline ≥2 log10 at week 12
Complete early virological response	cEVR	Undetectable HCV RNA at week 12
Partial early virological response	pEVR	HCV RNA decline ≥2 log10 at week 12
Relapse	RL	HCV RNA negative at the end of treatment and recurrence of HCV RNA during the follow-up of 24 weeks
Partial response	PR	HCV RNA decline ≥2 log10 at week 12 but positive at week 24 during Peg-IFN–RBV therapy
Null response	NULL	HCV RNA decline <2 log10 at week 12 during Peg-IFN–RBV therapy

Response at weeks 4 and 12 of pegylated interferon-α (Peg-IFN)-based regimens was used to determine the optimal treatment duration. Patients with a fast decline who achieved a rapid virological response (RVR) were eligible for short-term regimens without impairing sustained virological response (SVR) rates. By contrast, a poor response until week 12 of treatment identified patients in whom the chance of SVR was minimal and, therefore, treatment should be stopped early. Response-guided therapy minimized adverse events of Peg-IFN–ribavirin (RBV) therapy. Moreover, in those patients who failed antiviral treatment response during treatment, it was essential to estimate SVR chances for subsequent treatment attempts. HCV, hepatitis C virus.