Can Quantitative HBSAG Be A Reliable Surrogate Biology Essay

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Introduction: HBsAg is the chief protein of the viral envelops, and can be detected serologically and guided the diagnosis of hepatitis B infection. The HBsAg levels and their correlation with HBV DNA levels have shown contradicting results, with both positive and negative correlations. Material and methods: The objects were 74 CHB patients who were HBsAg-positive for more than 6 months. Quantitative HBsAg, HBV DNA, ALT and AST were measured in CHB patients. Results: The correlation between quantitative HBsAg and HBV DNA wasn't significant. We also couldn't find any correlation between Quantitative HBs Ag with ALT but the correlation between HBV DNA and ALT in this study was a significant. Conclusion: Finding the correlation between HBV DNA and quantitative HBSAg is very complicated. Many factors like, genotype of HBV virus, phase of infection, methods of measurement, HBeAg condition, drugs and types of treatment procedures, seems affected the results of the studies. So, in future investigations, attention to these variants can be helpful.

Key words: Quantitative HBsAg, HBV DNA, CHB

Introduction

Hepatitis B virus (HBV) causes a wide range of clinical consequences, from acute and chronic infection to cirrhosis and hepatocellular carcinoma (1). Its estimated 350 million persons worldwide are chronically infected with hepatitis B virus (HBV) (2). Hepatitis B surface (HBs) antigen (HBsAg) is the earliest serological indicator of acute hepatitis B virus (HBV) infection and a key diagnostic marker of chronic hepatitis B (CHB) infection when it persists in the serum for more than 6 months (3). HBsAg is the chief protein of the viral envelops, and can be detected serologically and guided the diagnosis of hepatitis B infection (4). In patients with chronic hepatitis B (CHB), there are several important viral components that have clinical importance and are measured routinely as part of disease management and the most common application is HBsAg measurement as qualitative test (5). Over recent years, there has been an increasing focus on quantitative HBsAg measurement and its use in the management of CHB. In patients treated with oral antiviral therapy, the HBsAg levels and their correlation with HBV DNA levels have shown contradicting results, with both positive and negative correlations (6-7). HBsAg seroconversion, characterized by the loss of serum HBsAg and development of anti-HBs antibodies, is the hallmark of a successful immunological response to HBV infection and the outcome to clinical cure. It is associated with favorable long-term clinical outcomes, including reduced incidence of cirrhosis and hepatocellular carcinoma and longer survival (8). Measuring serum HBV DNA is the gold standard for monitoring viral load, but it is relatively expensive and not yet readily available in some areas. By contrast, the technique for detecting quantitative HBsAg is fairly easy and inexpensive (9).In this study, we aimed to analyze the correlation between quantitative serum HBsAg and HBV DNA in chronic hepatitis patients.

Material and methods:

The objects were 74 CHB patients who were HBsAg-positive for more than 6 months and referred to a virology and molecular department of fajr medical laboratory in sari, Iran. Samples were frozen and stored at -20°C. AST and ALT levels were measured at time of sampling. Serum HBsAg was quantified by Elecsys 2010 analyzer (Roche Diagnostics GmbH, Penzberg, Germany) after 1:100 dilution. Briefly, the automatic Elecsys HBsAg II quantitative assay procedure is as follows: in the first incubation, two biotinylated monoclonal anti-HBs antibodies and a mixture of monoclonal anti-HBs antibody and polyclonal anti-HBs antibodies labeled with ruthenium form a sandwich complex with HBsAg in the sample. After the addition of streptavidin-coated microparticles, the complex becomes bound to the solid phase via the interaction of biotin and streptavidin. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier. Results are determined via a calibration curve which is instrument-specifically generated by 2-point calibration and a master curve provided via the reagent barcode. HBsAg was expressed in IU/ ml. HBV DNA viral load was determined using Rotorgene 6000 system (Corbet, Australia). SPSS 17 was used to analyze the data. Spearman correlation coefficient was used to correlate serum levels of HBsAg and HBV DNA levels. P ≤ 0.05 was considered significant.

Results

This descriptive study was performed to determine the correlation of serum HBSAg level and quantitative HBV DNA level in patients with chronic hepatitis B in the department of molecular research of Fajr medical laboratory, sari, Iran. Subjects included were 45 men and 29 women.

The mean HBV DNA serum level and quantitative HBs Ag were 2,400,061 (0 - 77,452,767) IU/mL and 4,100 (0 - 19,904), respectively. The serum concentrations of alanine amino transferase (ALT) and aspartate amino transferase (AST) were 47.2 (12 - 356) IU/L and 29 (14 - 137) IU/L respectively. The correlation between quantitative HBsAg and HBV DNA wasn't significant (Spearman ρ=0.15, p=0.21, n=74) by the Spearman correlation test. We also couldn't find any correlation between Quantitative HBs Ag with ALT (p=0.3) but the correlation between HBV DNA and ALT in this study was a significant (p<0.05).

Discussion

As HBsAg quantification indirectly reflects the number of infected hepatocytes (10). HBV DNA is a common tool to monitor treatment response. However, the HBV DNA test still has been considered to be an expensive and labor-intensive test but quantitative HBsAg test is a relatively simple and cost-effective test, and can be performed in a fully automated manner (7). In this study, we focused on the correlation between quantitative HBsAg and HBV DNA and the results revealed that the correlation between quantitative HBsAg and HBV DNA wasn't significant in CHB patients. Many studies tried to find whether quantitative HBsAg can be a surrogate marker of HBV DNA. In Some studies, such, Su et al. its reported that serum HBSAg concentration might serve as a surrogate marker of HBV DNA level in CHB patient (11) and some studies indicate on negative (12) Or no correlation (13). Diverse correlations between quantitative HBsAg and HBV DNA can depend on the conditions of each study. The results of such these studies, might be attributed to the fact that classification of HBV infection phases should be consider in similar study. Also, in this study has the limitation that all patients were not examined for HBeAg status. Hepatitis B e antigen is a marker that shows the phase of HBV infection. (HBeAg)-negative chronic hepatitis B (CHB) represents a late phase in the course of the infection (14). Jaroszewicz et al. reported that HBsAg showed a strong correlation (ρ=0.79, p<0.01) with HBV DNA during acute hepatitis B, but correlation of HBsAg and HBV-DNA was weak or absent when analysing different phases of persistent HBV-infection separately (15).

So, The HBV infection period might also be an important factor for a good correlation and in some studies indicated that the chronic HBV-infected patients without antiviral therapy in the early replicative phase is more suitable for adjusting quantitative HBsAg to reflect HBV DNA (16). Although we did not perform a genotyping test in this study, we can expect that most samples would be mostly HBV genotype D, because that is the HBV genotype of most Iranians (17). Recently, in some studies, association between HBsAg and HBVDNA was observed in patients infected with HBV-genotype D, but in Ganji et al. studiy and our study in two separated region of Iran, we couldn't find any correlation (4-18). There are controversy in role of HBSAg in prediction of treatment efficacy in CHB patients. Fung believed that the end-of-treatment and post-treatment HBV DNA levels is important indicators of treatment success and relapse, respectively. With newer and more powerful antiviral agents, and with the development of quantitative assays that are highly sensitive (19). In contrast, Wiegad J et al. are in this opinion that Quantitative HBsAg and HBeAg cannot substitute for HBV DNA quantification during the assessment of antiviral therapy; however, the decline of HBsAg does predict eventual HBsAg clearance (20). Finding the correlation between HBV DNA and quantitative HBSAg is very complicated. Many factors like, genotype of HBV virus, phase of infection, methods of measurement, HBeAg condition, drugs and types of treatment procedures, seems affected the results of the studies. So, in future investigations, attention to these variants can be helpful.

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