The availability of clinical molecular tests for detection and quantitation of HBV DNA in serum has improved our understanding of the clinical manifestations and natural history of HBV infection and facilitated the monitoring of response to therapy. However, the use of increasingly sensitive tests for this purpose has led to new questions and dilemmas. For example, most patients with chronic HBV infection have detectable HBV DNA in serum when sensitive PCR assays are used, even in HBsAg carriers without apparent disease. This leads to the question of what serum level of HBV DNA should be used to determine the need for treatment. Likewise, because of the limitations of currently available therapies, most treatment responders continue to have HBV DNA detectable in serum when the most sensitive assays are used.19 This raises the questions of when to stop treatment and how virologic treatment response should be defined.
Early studies using insensitive hybridization assays demonstrated that most patients who developed spontaneous or treatment-induced anti-HBeAg seroconversion with undetectable serum HBV DNA have normal ALT levels, reduced histologic activity, decreased risk of hepatic decompensation, and improved survival.20 The majority, however, have detectable HBV DNA when PCR assays are used. Therefore, it seems that patients with low serum HBV
DNA levels may not require treatment. Although there appears to be a level of serum HBV DNA below which hepatitis B is inactive and nonprogressive, this level may range from 104 to 106 genome copies/ml and may vary with the patient and the assay used to determine the levels. There is poor agreement between HBV DNA results generated with the different assays.15,21
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