Detection of hepatitis B virus (HBV)
DNA in serum allows monitoring of HBV replication and assessing responses to
antiviral treatment. HBV
DNA quantification measures virus replication and can be used as a prognosis
indicator of
liver disease and an index of response to
antiviral drugs. The aim of this study was to compare the performances of three HBV
DNA detection and/or quantification techniques for assessing HBV replication. Three hundred unselected sera with a request for HBV
DNA detection and quantification were tested with a molecular hybridisation technique without amplification (Digene Hybrid-Capture, Murex Diagnostics Ltd), a signal amplification assay based on branched
DNA technology (Quantiplex HBV
DNA,
Chiron diagnostics), and an 'in-house' qualitative, non quantitative target amplification assay based on the polymerase chain reaction (PCR) with primers located in the S gene of the HBV genome. Hybrid-capture and branched
DNA gave concordant results in 278 cases (93%). In the 128 samples positive by both assays,
DNA titres in pg/ml were related significantly (r = 0.70, P < 0.0001). but branched
DNA titres increased more rapidly than hybrid-capture titres when the amount of HBV
DNA in the sample increased. Twenty-two sera (7%) were negative by hybrid-capture, but positive in branched
DNA (detection rate gain: 15%). In these 22 patients,
DNA titres were low,
HBsAg was present in all instances and
alanine aminotransferase activity was elevated in 18 patients (82%);
HBeAg was present in seven patients (32%) and anti-HBe
antibodies in 18 patients (82%); liver biopsy, undertaken in 18 patients, revealed
chronic active hepatitis in all instances, associated with
cirrhosis in eight cases. Qualitative, non-quantitative HBV
DNA PCR was positive in 75 (50%) of the 150 hybrid-capture-negative, branched
DNA-negative samples, including a significant proportion of patients without evidence of ongoing HBV-related
liver disease. The results show that in general, the branched
DNA assay detects HBV
DNA in more patients than hybrid-capture and that this improved detection rate is relevant clinically and genome equivalents/ml are preferred to pg/ml to quantify HBV
DNA in clinical specimens and finally qualitative, non-quantitative polymerase chain reaction can detect HBV
DNA in patients without evidence of active HBV-related
liver disease. This study emphasizes the need for more sensitive, university standardised quantitative HBV
DNA assays and for the definition of clinically relevant cutoffs with these assays.