Is Quantitative HBsAg measurement a reliable substitute for HBV DNA quantitation?

Hepatitis B surface antigen (HBsAg) is one of the main proteins of HBV envelop and its serum quantitative measurement is the most common quantitative test for monitoring the progress of Chronic Hepatitis B. Although measurement of serum HBV DNA copy number is a gold standard method for displaying viral load, the test is relatively expensive and it is not readily available everywhere in the world, while quantitative detection of HBsAg is fairly easy and inexpensive. The aim of this study was to investigate the correlation between serum HBsAg level and HBV DNA copy number in patients with chronic HB. Quantitative HBsAg, quantitative HBV DNA, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) serum levels were tested in 74 patients with chronic hepatitis B infection - who were HBsAg -positive for more than 6 months. In order to find any correlation between the results of these methods, Spearman and Kruska- Wallis correlation coefficient tests were applied. No significant correlation was observed between quantitative HBsAg and HBV DNA measurements. Also, we could not find any correlation between serum HBsAg and ALT levels. But, serum HBV DNA content and AST level had a significant positive correlation. There are many factors affecting the correlation between serum HBV DNA copy number and HBsAg level such as genotype of HBV virus, phase of infection, methods of measurement, HBeAg status, and drug and types of treatment procedures. Therefore, these factors should be considered in further studies dealing with the correlation between quantitative HBV DNA and HBsAg tests.