High proportion of hepatitis B virus-infected patients at a mild stage of disease progression: a cross-sectional study in a single reference laboratory in Cameroon

¹Centre Pasteur, Yaounde, Cameroon, ²Faculty of Medicine and Biomedical Sciences, University of Yaounde I, Yaounde, Cameroon

^&Corresponding author
Pretty Rosereine Mbouyap, Centre Pasteur, Yaounde, Cameroon

Introduction    

Chronic hepatitis B (CHB), defined as persistence of hepatitis B surface antigen (HBsAg) for six months or longer, is a major public health problem. Worldwide, there are an estimated 296 million chronically infected persons, and nearly 650,000 Hepatitis B Virus (HBV)-related deaths are recorded every year. Cirrhosis and hepatocellular carcinoma are the main complications. Among people with a chronic infection, between 20 and 30% could develop complications [1].

The Western Pacific region and Africa are home to the majority of infected people, where almost 68% of HBV-related deaths are recorded. [2]. However, in Africa, only 1% of people infected with HBV are screened, and of these, very few benefit from antiviral treatment [2]. In Cameroon, the prevalence of HBV-infected patients is 11.2%, which classifies it as a high-prevalence area [3]. This is why a global strategy to combat viral hepatitis has been drawn up by the World Health Organization (WHO), intending to eliminate viral hepatitis as a health problem by 2030 [4]. WHO launched a global program against hepatitis B and C infections, whose aim by 2030 is to reduce the number of new cases of viral infections by 90%, reduce the number of hepatitis related deaths by 65%, and treat 80% of viral hepatitis infections. The main targeted interventions are vaccination of infants, screening and treatment of persons at risk [5].

The initiation of treatment for an HBV-infected patient depends on certain eligibility criteria defined by learned societies taking into account the different phases of the evolution of liver disease. Chronic HBV infection has different phases, which can be identified by the simultaneous use of some virological, serological and biochemical markers involved in monitoring the progression of the disease [5]. The surveillance of markers is essential for determining the different stages of the disease, adopting appropriate treatment and making the right decisions. [6]. These phases are not necessarily successive or sequential. They are defined by a new classification from the European Association for the Study of the Liver (EASL). The natural history of HBV infection can be divided into 5 phases based on the presence or absence of hepatitis B e antigen (HBeAg), the level of viral replication, the level of alanine aminotransferase (ALT) and the presence of histological lesions of inflammation or fibrosis in the liver [2]. There are five stages of HBV infection namely: (I) HBeAg-positive chronic infection, (II) HBeAg-positive chronic hepatitis, (III) HBeAg-negative chronic infection, (IV) HBeAg-negative chronic hepatitis and (V) HBsAg-negative phase. This classification is mainly based on the description of the two characteristics of chronicity, namely infection and hepatitis [7]. antiviral treatment against HBV aims to prevent, halt or reverse the progression of liver disease towards cirrhosis and liver cancer [1,7].

Patients with advanced life-threatening liver disease such as acute liver failure and cirrhosis should be treated. Individuals with minimal fibrosis and a low risk of CHB progression are not usually considered for treatment, but these individuals should be identified and followed over time [1]. It will be necessary to classify HBV-infected patients to identify patients who require treatment. This study aimed to determine the relationship between serological, biochemical, and virological markers involved in the follow-up of patients with CHB infection at Centre Pasteur du Cameroun (CPC).

Methods     

Study setting and design: this was an analytical cross-sectional study of the electronic records of patients with chronic HBV infection, recorded in the Laboratory Information System (LIS) of the CPC over ten years from January 2011 to December 2021.

Study site: CPC is a technical establishment of the Ministry of Public Health of Cameroon and a reference laboratory for diagnosing and monitoring various infections in Cameroon, including HBV. The medical analysis laboratories (LAM) of the CPC have an accredited quality management system according to the international standard ISO 15189 (TUNAC) for hepatitis B diagnostic markers: hepatitis B surface antigen (HBsAg), anti-HBs antibody, anti-HBc antibody and HBV viral load (HBV VL). As such, this facility receives patients from across the country for routine screening and monitoring.

Enrolment of study participants: we retrieved from the CPC LIS the results of ALT, HBeAg serology, and HBV VL of HBV-infected patients (HBsAg-positive) aged over 18 years. Only patients who had carried out all three analyses performed in the biochemistry, serology and virology between January 2011 and December 2021 were included in this study.

Procedure for ALT measurement: ALT was measured photometrically by measuring the decrease in absorbance using the Roche/Hitachi, Cobas c 501, according to the manufacturer's instructions. Normal values for ALT were ≤40 IU/L irrespective of sex.

Detection of HBsAg and HBeAg: these serological analyses were performed respectively using the ARCHITECT HBsAg qualitative II assay (Abbott i1000sr) and the ARCHITECT HBeAg assay (Abbott i1000sr); for the qualitative detection of HBsAg and HBeAg in serum and plasma, respectively using a chemiluminescent microparticle immunoassay (CMIA), according to the manufacturer's instructions. Positive results for HBsAg were confirmed using the ARCHITECT HBsAg qualitative II confirmatory (Abbott i1000sr).

HBV Viral Load determination: the automated Abbott Real Time HBV m2000 system was used to extract and quantify HBV DNA levels. Abbott RealTime HBV assay is an in vitro polymerase chain reaction (PCR) assay for use with the Abbott m2000 System DNA reagents and with the Abbott m2000sp and m2000rt instruments for the quantitation of Hepatitis B Virus (HBV) DNA in human serum or plasma (EDTA) from chronically HBV-infected individuals. The detection limit was 10 IU/mL.

Classification into the different phases of chronic HBV infection: chronic HBV infection phases were classified based on EASL [4].

Phase 1: HBeAg-positive chronic HBV infection, previously termed "immune tolerant" phase; characterised by the presence of serum HBeAg (>10⁷IU/mL, very high levels of HBV DNA and ALT persistently (≤40 IU/L).

Phase 2: HBeAg-positive chronic hepatitis B is characterised by the presence of serum HBeAg, high levels of HBV DNA (10 4-10⁷), elevated ALT (>40 IU/L).

Phase 3: HBeAg-negative chronic HBV infection, previously termed 'inactive carrier' phase or "immune control phase", is characterised by undetectable or low (<2,000 IU/mL) HBV DNA levels and normal ALT (≤40 IU/L).

Phase 4: HBeAg-negative chronic hepatitis B is characterised by the lack of serum HBeAg, persistent or fluctuating moderate to high levels of serum HBV DNA (often lower than in HBeAg-positive patients), as well as fluctuating or persistently elevated ALT values (>40 IU/L).

Phase 5: HBsAg-negative phase is characterised by negative serum HBsAg and positive antibodies to HBcAg (anti-HBc), with or without detectable antibodies to HBsAg (anti-HBs). This phase is also known as "occult HBV infection".

Statistical analysis: the collected data were revised, coded and entered into IBM Statistical Package for the Social Sciences (SPSS®), version 22 (SPSS Inc., IBM Corp., Armonk, NY, USA). Quantitative data are presented as means, standard deviations (SD) and ranges, whilst qualitative data are presented as numbers and percentages. Comparisons between two groups were done using the Wilcoxon-Mann-Whitney test for non-parametric continuous variables and Student's t-test for parametric quantitative variables, whilst qualitative data were compared using the chi-squared test or Fisher's exact test when the expected count in any cell was found to be <5. The confidence interval (CI) was set to 95% and the accepted margin of error was set to 5%. The p-value was considered statistically significant at p≤0.05.

Ethical considerations: data set had been stripped of all possible identifiers and coded before analysis. No additional laboratory tests were performed other than those requested by the clinician, and there were no supplementary data were collected. As such, no ethical approval was required.

Results     

Demographic characteristics of the study population: a total of 1652 patients with all three results for HBV VL, HBeAg serology and ALT levels were extracted. This study population was 726 women (43.9%) and 926 men (56.1%). The age distribution was similar in both the male and the female population. The median age of females was 31 [25-38] years, and that of males was 33 [26-40] years. The most represented age groups were the young adult population aged 25-34 and 35-44 years. The age and sex distribution are shown in Figure 1.

Regarding biological parameters, ALT levels ranged from 5 to 1962 IU/L with a mean value of 55.8±3.2 IU/L and a median of 33 [24;49] IU/L. AST ranged from 9 to 4645 IU/L with a mean of 45.4±3.3 IU/L and a median of 30 [23;40] IU/L. HBV VL ranged from below 10IU/mL to 10⁹ IU/mL with a mean of 1.6x10⁷±2.5x10⁶ IU/mL and a median of 502.0 [77;3518] IU/mL. Mean and median values of all biological parameters were higher in males compared to females as detailed in Table 1.

Most participants had normal values of liver transaminases (n= 1080,65.5%) for ALT and (n=1255, 76.2%) for AST, low HBV VL below 2000 IU/mL at (n= 1131,68.5%) and (n=1489,90.1%) were HBeAg negative. Regarding HBV stage, most participants fell in stage 3 (n=1025, 62.0%), representing the relatively mild HBeAg-negative chronic HBV infection. All biological parameters, including ALT, AST, HBV VL and HBeAg were significantly higher in males compared to females (Table 2). Also, HBV stage 2 and 4, indicative of chronic hepatitis were significantly higher in males compared to females (Table 2). Concerning the association between biological parameters and two categories of age groups, no statistically significant association was found with the biochemical parameters (Table 2). Higher HBV VL and HBeAg positives were noted in the ≤30 years age group (Table 2). Also, HBV stage 2 (HBeAg positive chronic hepatitis) was significantly higher in the ≤30 years age group compared to the >30 years (Table 2).

Virological, serological and biochemical characteristics of the study population: HBV VL <2000 IU/mL was detected in 1131/1652 (68.4%) participants. Two hundred and ninety-five participants (17.8%) had HBV VL between 2000 and 20,000 IU/mL while 226/1652 (13.6%) participants had values >20,000 IU/mL. There was a significantly higher proportion of HBeAg-positive patients with viral loads >20,000 IU/mL (n= 116, 71.2%) compared to HBeAg-negative patients (n=110, 7.4%) with an odds ratio of 30.9 (Table 3). Also, a high proportion of patients with HBV VL >20,000 IU/mL had significantly higher liver transaminase levels (n=138; 24.3% ALT and n=111; 28.2% AST) compared to their opposite counterparts with HBV VL ≤20,000 IU/mL (n=88; 8.1% ALT and n=115; 9.2% AST; P<0.001).

Discussion     

This study aimed to determine the relationship between serological, biochemical, and virological markers involved in the follow-up of patients with CHB infection at CPC. We reported the virological, serological and biochemical characteristics of chronically HBV-infected patients at CPC to identify the association between socio-demographic and biological parameters and to determine the proportion of patients in different stages of chronic HBV infection. More than half of the participants were men, and this group had higher HBV VL and ALT levels and a higher prevalence of HBeAg-positive serology. These findings are similar to studies conducted by Tufon et al. and Meriki et al. in Cameroon in 2017 and 2021, in which men were the highest represented population at 64.3% and 55.7%, respectively [6,8]. Liver complications were more common in men than in women in some studies, and this was not related to environmental or behavioural factors [9,10]. Chronic liver disease may be influenced by the action of estrogens, which may have a protective and defensive role for liver cells [11,12]. There is an apolipoprotein (A-I) found only in male hepatocytes. This was discovered by the Chinese and could predispose to HBV infection and associated complications [13]. Estrogens produced in women can slow the progression of liver disease and limit complications [6].

In the study carried out by Esmaeelzadeh et al. in Iran, almost 59% of participants had transaminases above 40IU/ml and mean HBV-DNA level was 7.7±1.5×10⁵ IU/ml, ranging from zero to 14 10⁷ IU/ml [14]. This indicates a level of viral replication associated with hepatic cytolysis in a majority of cases. However, in our study, a low level of viral replication and a low level of hepatic cytolysis were observed. Regarding HBV stage, 62.0% of participants fell in phase 3. A similar result was found by Tufon et al. where almost 76% of participants were in phase 3 (immunocontrol) and only 18.4% of the participants fell in phase 2, while 4 were considered as the category of individuals who should be considered for treatment [6]. This is because we used the same HBV DNA viral load thresholds to classify patients into the HBeAg-negative chronic HBV infection phase.

The correlation between the level of viral load and transaminases has often been investigated in several studies. Some studies have shown a correlation between viral load and ALT [14-21]. These results are in line with those found in our study. In this way, the level of viral replication can be revealed by the ALT level. This can be an element of monitoring in our context of countries with limited resources, where molecular biology platforms are not always available.

This study also shows that many HBV-infected people are HBeAg negative and have low viral loads. Since HBV DNA levels, ALT levels, and HBeAg status are among the most important determinants of the risk of progression to cirrhosis, our participants are likely to have minimal or no liver damage [6]. The patients with HBeAg-negative CHB in this study tended to be older than those with HBeAg-positive CHB. Chu et al. 2007 reported that persistent HBeAg seropositivity beyond 40 years of age is relatively uncommon and is associated with a higher risk of cirrhosis and HCC [22].

There was a significantly higher proportion of HBeAg-positive patients with viral loads >20,000IU/ml compared to HBeAg-negative patients (p<0.001). A study has reported that HBeAg-positive CHB patients tend to have higher viral loads than HBeAg-negative patients [23]. Fouad et al. in Egypt in 2020 showed that a significant proportion (87.5%) of HBeAg-positive patients had HBV DNA levels greater than 2x10⁴ IU/mL, but this was not significantly higher than HBV DNA levels in HBeAg-negative patients (68%) [23]. Additionally, 7.4% of our study population had high HBV VL >20,000 IU/mL and were HBeAg negative. Since certain preC/C mutations have been associated with significant virological or clinical events, such as liver disease progression, or HBeAg seroconversion [24,25], it is likely that these individuals harbour preC/C mutants that should be further investigated.

The limitation of this study was the lack of information on the treatment status of HBV-infected patients, which limits the robustness of the study.

Conclusion     

Our study unveiled that a high proportion of HBV-infected patients referred at CPC have normal values of biological parameters and thus are at a mild stage of disease progression. These results indicate that a small proportion of HBV-infected patients referred at CPC may ultimately be eligible for treatment according to the EASL classification. However, the presence of negative HBeAg serology in patients with high HBV VL levels also would suggest the presence of HBV pre-C mutant in this population that requires further investigation.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Conception and study design: Pretty Rosereine Mbouyap, Richard Njouom. Data collection: Pretty Rosereine Mbouyap, Laure Ngono, Annie Epote, Suzanne Belinga and Fréderic Lissock. Data analysis and interpretation: Pretty Rosereine Mbouyap, Jeanne Manga, Chavely Gwladys Monamele and Richard Njouom. Manuscript drafting: Pretty Rosereine Mbouyap. Manuscript revision: Richard Njouom. All authors read and approved the final version of the manuscript.

Acknowledgments     

We would like to thank the medical paramedical staff of Centre Pasteur du Cameroun and all participants of this study

Tables and figure     

Table 1: description of study participants demographic and biological characteristics

Table 2: comparison of biological parameters by sex and age

Table 3: HBV VL compared with demographic, immunological and biochemical characteristics

Figure 1: age and sex distribution of the study population

References