Precision and stability of hepatitis B virus DNA levels in chronic surface antigen carriers

Quantitative determination of hepatitis B virus (HBV) DNA concentration is the most important measure for an estimation of the infectivity of an HBV positive health care worker and the basis for the decision whether he or she is allowed to perform exposure prone procedures. Thus questions are raised on how reliable quantitative HBV DNA assays are, and how stable is the HBV DNA concentration is in a healthy chronic HBV carrier. Therefore, in the present study two commercially available quantitative HBV DNA assays, the Amplicor HBV Monitor and the HBV Test Hybrid Capture II, and an "in house" quantitative HBV TaqMan PCR, analysing 101 sera of HBsAg positive patients for HBV DNA were compared. In addition, HBV DNA concentrations were followed in 14 healthy chronic carriers for up to 6 years. Despite a good overall correlation between the three tests considerable differences were found for the results of individual sera. Fifty-one percent of sera showed differences within one order of magnitude, 45% differed by a factor above 10 and 4% even by a factor of 100 and higher. The follow-up of the HBV DNA concentrations in 14 carriers showed in 7 carriers a rather stable course with variations within one order of magnitude, whereas in the other half the DNA concentrations fluctuated by factors between 10(2) and 10(6) over the observation period. Thus, viral load determinations in health care workers have to be interpreted with some caution, especially when they are the basis of far-reaching decisions.