This has also been observed in patients treated with nucleos(t)ide therapy (lamivudine, adefovir or tenofovir) with reduced rates of eAg seroconversion in patients with a baseline HBV DNA >7 log10 IU/mL

[102]. During therapy, HBV DNA testing is used to decide whether to continue or stop interferon treatment (see ‘Therapy’, section 4.3 below) [101]. This also applies to nucleos(t)ide therapy where primary nonresponse is defined as a <1 log10 IU/mL drop in HBV DNA level from baseline at 3 months, and response is defined as an undetectable HBV DNA by real-time polymerase chain reaction (PCR) assay within 48 weeks of therapy. Partial virological response is defined as a >1 log10 IU/mL drop in HBV DNA but detectable HBV DNA by real-time PCR assay [101,102]. In HIV-uninfected patients, a partial virological response should lead to a decision about modifying therapy at 24 weeks of therapy for lamivudine and telbivudine (which have BYL719 a low barrier to resistance) and at 48 weeks for entecavir, adefovir and tenofovir (which have a high barrier to resistance) [102]. How this should be applied in coinfected patients is uncertain. Virological breakthrough on treatment, defined as a confirmed increase of >1 log10 IU/mL above nadir HBV DNA level on therapy, means either nonadherence or resistance [102]. The lower limit of detection of the assays used to monitor HBV DNA should be 10–15 IU/mL and this level should also be the aim of treatment

[103]. Measurement of HBV DNA every 6–12 months is sufficient if the patient is not on HBV therapy [104]. 4.2.2.2 Measuring HBV serology during and after therapy. selleck kinase inhibitor The ideal outcome of treatment is HBe seroconversion in patients who are HBeAg positive and HBs seroconversion (very rare) in all patients [102]. Once HBV DNA is undetectable, HBeAg and eAb in HBeAg-positive patients and HBsAg in all patients should be tested every 12–24 weeks to pick up seroconversion. It should be noted that there

is no HBV DNA level at which seroconversion from HBeAg positive to negative is completely predictable [105]. Spontaneous or treatment-induced seroconversion from HBsAg positive to negative PIK3C2G is associated with ongoing undetectable HBV DNA but, in patients who convert from HBeAg positive to negative, HBV DNA may still be detectable at low levels [102,106]. 4.2.2.3 HBV resistance testing. Resistance testing is becoming more widely available and may be considered as a baseline pretreatment, especially if there is a history of previous exposure to anti-HBV drugs, as a means to inform treatment decisions in those with nonresponse to treatment or with virological breakthrough. A line probe assay for the detection of hepatitis B wild-type virus and a drug-induced mutation using direct sequencing can identify specific resistance mutations [107,108]. Direct sequencing of the HBV polymerase gene can detect variants that are present in 10–20% of the virus population [109].