Correlation of quantitative assay of hepatitis B surface antigen and HBV DNA levels in asymptomatic hepatitis B virus carriers

OBJECTIVE: This study was to elucidate the correlation between quantity of hepatitis B surface antigen (HBsAg) and hepatitis B virus (HBV) DNA levels in asymptomatic carriers. METHODS: Based on the presence of the hepatitis B e antigen (HBeAg) and HBV DNA levels, 67 asymptomatic carriers were divided into four groups. HBV DNA was determined by hybridization (sensitivity 141 500 copies/ml) and polymerase chain reaction (PCR, sensitivity < 10 copies/ml). Cases of groups I (n = 18), II (n = 17) and III (n = 16) were negative for HBeAg and had HBV DNA levels of < 10 (PCR undetectable), 10 to 10 (PCR detectable) and > 10 copies/ml (hybridization detectable), respectively. Cases of group IV (n = 16) were positive for HBeAg and high HBV DNA levels (> 2 x 10 copies/ml). HBsAg was determined quantitatively by the ARCHITECT HBsAg assay. RESULTS: Our data showed HBsAg levels were correlated with HBV DNA (r = 0.709; P < 0.001) on a log scale. The mean log HBsAg (IU/ml) of groups I, II, III and IV were 2.68 +/- 0.8, 2.93 +/- 1.03, 3.22 +/- 0.45, 4.83 +/- 0.19, respectively. That of group IV was significantly higher than the mean log HBsAg of any other group (P < 0.001). The best cut-off for HBsAg in differentiating group IV from other groups was 15 000 IU/ml with both sensitivity and specificity of 100%. That of group I was significantly lower than those of group III (P = 0.035) and IV (P < 0.001). The best cut-off in differentiating group I from the other groups was 1600 IU/ml with a sensitivity of 69.4% and a specificity of 66.7%. CONCLUSION: Quantitative measurement of HBsAg titres may be an easy and economical reference for HBV replication in HBV carriers.