Absolute viral load was found clinically useful in predicting sustained virological response and lack of sustained virological response to treatment.
Log decline in viral load from baseline was also found useful in predicting sustained virological response and non-sustained virological response to treatment.
Dr Terrault and colleagues assessed the clinical utility of Hepatitis C virus RNA quantitation and changes in viral load.
The researchers included 351 Hepatitis C-infected individuals treated with interferon plus ribavirin.
The team showed that viral load decision thresholds provided negative predictive values of more than 95% at week 4 using a 100 000 IU/mL cut-off.
The researchers found similar results at weeks 8 and 12 using 10 000 IU/mL cut-offs.
|A 2-log decline from baseline provided 95% negative predictive values at week 8|
|Journal of Viral Hepatitis|
The team noted that a 2-log decline from baseline provided negative predictive values of more than 95% at weeks 8 and 12.
Combinations of absolute viral loads and viral load from baseline did not enhance the performance of the rules for predicting non-sustained virological response.
The positive predictive values at weeks 8 and 12 were 59% and 67%, respectively.
The team noted that the results highlight the importance of viral quantitation in gauging therapeutic response in chronic Hepatitis C with antiviral therapy.
Dr Terrault's team concluded, “Early changes in viral load, measured as absolute viral loads or change in viral load from baseline, are highly predictive of non-sustained virological response at 8 and 12 weeks.”
“Positive predictive values are modest but these data may provide encouragement to patients who are in the early phases of treatment when side effects are frequent.”
“Additionally, we demonstrated the need for cautious interpretation of stopping rules when the values are at or near the decision thresholds.”