Effect of Strain on Treatment

At the outset, a significant factor influencing your response to treatment is the genotype of the virus that you are infected with:

Genotypes 1 and 4

Genotype 1 is generally regarded as being the most difficult to treat so combination antiviral therapy, when given, is usually continued for the longer 48 week period. After the first 12 weeks of treatment, you will be asked to provide a blood sample to run a 'twelve week predictability test'. This will determine your progress so far and whether continued treatment is likely to be successful.

Genotype 4 is also regarded as being more difficult to treat and where combination anti-viral therapy is used, the treatment is also typically continued for 48 weeks. After the first 12 weeks of treatment, you will be asked to provide a blood sample to run a 'twelve week predictability test'. This will determine your progress so far and whether continued treatment is likely to be successful.

Genotypes 2 and 3

In contrast, genotypes 2 and 3 are widely considered to respond well to antiviral treatment compared to other genotypes. Treatment with antiviral combination therapy for genotypes 2 and 3 is usually for a 24 week (roughly 6 month) period.
After the first 12 weeks of treatment, you may or may not be asked to provide a blood sample to run a 'twelve week predictability test'. This depends entirely on your consultant and perhaps your tolerance of the treatment.

It is generally accepted that the 12 week predictability test does not need to be undertaken routinely for genotypes 2 and 3 because the success rate for these genotypes with antiviral treatment is high. However, if a patient is experiencing significant side effects the results of the 12 week predictability test can assist in decisions regarding how best to managing your treatment regime.