The Cobas Amplicor HBV Monitor test for quantitative determination of hepat
itis B virus (HBV) DNA in serum has recently been introduced. To evaluate t
he performance of this assay in a routine diagnostic laboratory, reproducib
ility of results was determined with the First European Union Concerted Act
ion HBV Proficiency Panel and the Accurun 325 HBV DNA Positive Control, Ser
ies 300. Results for 270 routine serum samples were additionally evaluated.
To avoid the retesting of a large number of samples due to titers exceedin
g the upper limit for the linear range of the assay, sera of patients with
chronic hepatitis B (CHB) were diluted prior to the assay to 10(-4) in norm
al human plasma, which is included in the assay. The mean coefficient of va
riation was 22.9% for all input HBV DNAs. Of 270 routine serum samples, 182
(150 sera from transplant donors and 32 sera from patients who had recover
ed from CHB) tested negative. Eighty-six sera were found to be HBV DNA posi
tive; in six sera, HBV DNA levels were found to exceed the upper limit for
the linear range of the assay and had to be retested. In the remaining two
sera, inhibition occurred. The semiautomated Cobas Amplicor HBV Monitor tes
t showed sufficient reproducibility and helped in avoiding human error. The
relatively narrow linear range of detection is a limitation of the new ass
ay.