During treatment with pegylated interferon plus ribavirin, plasma HCV RNA decreases with a rapid first phase and a slower second phase, the study authors noted as background.

In this analysis, the researchers compared the magnitude (size) and slope (speed or rate) of viral load decline during the first 48 hours of treatment with pegylated interferon alfa-2a (Pegasys) plus ribavirin in patients who did and did not achieve RVR, defined as undetectable HCV RNA (< 50 IU/mL) at week 4.

The study included 23 patients with genotype 1 or 4 HCV (14 monoinfected and 9 HIV/HCV coinfected). Plasma HCV RNA was measured at baseline, at 48 hours, and at weeks 1, 2, 4, 8, 12, 48, and 72. HCV viral load decrease, slope of the decrease, and the efficiency factor (epsilon) were determined in the first 48 hours after the start of therapy.

Results

5 HCV monoinfected participants (36%) and 3 HIV/HCV coinfected patients (33%) attained RVR at week 4.
6 monoinfected patients (43%) and 5 coinfected patients (56%) achieved SVR at 24 weeks after completion of therapy.
The 5 HCV monoinfected participants who attained RVR demonstrated both a larger decrease in HCV viral load and a steeper slope (faster decline) compared to the 9 monoinfected patients without RVR.
HCV RNA change: 1.77 vs 0.66 log10 IU/mL, respectively (P = 0.019);
HCV RNA slope: 2.04/day vs 0.76/day, respectively (P = 0.019).

Among the coinfected participants, however, a significant association between HCV RNA decline at 48 hours and RVR was not observed.
When looking at participants who achieved SVR, larger HCV RNA decline and steeper slope at 48 hours were seen in both HCV monoinfected and HIV/HCV coinfected patients.


Based on these findings, the study authors concluded, "in the first 48 hours after the start of therapy, HCV monoinfected patients with an RVR have a larger viral load decrease, steeper viral slope, and a higher efficiency factor as compared with non-RVR patients."

Early response at week 12 is commonly used to decide whether patients can stop interferon-based treatment that is unlikely to produce a sustained response. Numerous studies have shown that RVR at week 4 is also a good predictor of SVR. This study suggests that even very early response at 48 hours may be a predictive factor, at least among HCV monoinfected patients.

Departments of Internal Medicine and Infectious Diseases, Medical Microbiology, Gastroenterology, and Immunology, University Medical Center Utrecht, Utrecht, Netherlands; Department of Gastroenterology, Onze Lieve Vrouwe Gasthuis, Amsterdam, Netherlands; Department of Internal Medicine and Infectious Diseases, Erasmus Medical Center, Rotterdam, Netherlands.


JE Arends, JC Stuart, LC Baak, and others. Plasma HCV-RNA decline in the first 48 h identifies hepatitis C virus mono-infected but not HCV/HIV-coinfected patients with an undetectable HCV viral load at week 4 of peginterferon-alfa-2a/ribavirin therapy. Journal of Viral Hepatitis 16(12): 867-875. December 2009.