Abbreviations:

ALT: Alanine aminotransferase; Anti-HBs: Antibody to Hepatitis B surface; Anti-HBcore: Antibody to hepatitis B core antigen; CHB: Chronic hepatitis B infection; HBV: Hepatitis B infection; HBsAg: Hepatitis B surface antigen; HBV DNA: Hepatitis B infection DNA; HCV: Hepatitis C infection; HIV: Human immunodeficiency virus; WHO: The World Health Organization.

Introduction

According to the World Health Organization (WHO) approximately 1.5 million people become infected HBV each year [1], with around 240 million chronic carriers worldwide [2,3]. Kazakhstan is ranked as one of the countries with medium endemicity (2-7%) [4]. In terms of the prevalence of HBV in Kazakhstan, the peak incidence in 2020 was defined in West Kazakhstan, Kyzylorda region and in the city of Nur-Sultan rather than the national average prevalence [5].

Anti-HBc is considered as an informative marker of occult HBV infection and present in the chronic carrier state and at the end of an acute resolving infection [6].

The results of Croatian study [7] showed that the anti-HBc prevalence among blood donors is 1.32.%.  The study by Meffre C. et al. [8] showed that the overall anti-HBc prevalence was 7.3% among metropolitan residents in France. In Germany population the anti-HBc prevalence of whole population was defined as 8.71% [9].

Considering these data are among the highest of infectivity results worldwide, another study of known risk and behavior factors and their association with positive HBV markers was performed in parallel. It was observed that tobacco smokers with hepatocellular carcinoma most often develop HBV infection [10,11]. Individuals with chronic HBV infection that consume high levels of alcohol are at a higher risk of alcoholic liver disease [12].  Also, patients with HBV-associated liver failure suffer from insufficient nutrition with high risk for the impairment of intestinal function [13]. Although HBV risk factors have been widely studied in Western countries, they are less analyzed and documented in Kazakhstan.

The primary objective of this study is to investigate the correlation between positive Hepatitis B serology markers and various risk and behavior factors. The aim is to address the current gap in knowledge and offer valuable insights into the epidemiology and determinants of HBV infection in Kazakhstan. Ultimately, the study intends to make a meaningful contribution through the development of targeted public health programs aimed at prevention and control of HBV infection within the country.

Materials and Methods

Study design

A cross-sectional study aimed at investigating anti-HBc was conducted in the period between June 1 to July 22, 2021 at the Scientific-Production Center of Transfusiology, Ministry of Healthcare, in Kazakhstan.

Approval for the study was obtained from the Ethics Commission (Decision of EC #5 from 20 August 2020). A specific donor questionnaire was created outlining the study purpose and to obtain information regarding the donors’ sociodemographic characteristics, nutrition habits (eating vegetables and fruits), diet (main meal), at risk factors (smoking, alcohol consumption, dyslipidemia, HBV-infected family members, blood transfusion, intravenous or intramuscular procedures, tattooing or skin piercing, and surgical interventions). Also, cholesterol disorder was determined through self-reporting on the questionnaire.

Inclusion criteria

The study included blood donors who satisfied the donation criteria, which encompassed individuals aged 18 and above, with no history of blood donation within the past 3 months, weighing more than 50 kg, and testing negative for Hepatitis B, Hepatitis C, HIV, syphilis, gonorrhea, and other relevant laboratory parameters as per the stipulated requirements for blood donation. 68.9% of recruited donors were on regular basis of blood donation. HBsAg found to be positive for 3.4 % individuals from initial screening, while first time blood donors demonstrate more than twice higher HBV infectivity than regular blood donors [5].

Exclusion criteria

Potential blood donors were not engaged to participate in the study if did not meet inclusion criteria.

Laboratory analysis

The samples initially were tested for anti-HBc. If found to be positive with anti-HBc, further testing for anti-HBs was performed. All reagents for Hepatitis B screening were associated with the Architect i2000SR, Abbott system.

ALT markers were tested using Biosystems A25 analyzer. The confirmatory tests for infectious markers were evaluated by NAT in pools of six samples by Cobas TaqScreen MPX Test v.2.0

Statistical analysis

Statistical analysis was conducted by the R software (version 4.1.1, USA, 2021) [14]. Descriptive statistics were reported as proportions (%) for categorical variables and as means±standard deviations for continuous variables. The normality of the distribution was assessed using the Kolmogorov-Smirnov test.

Categorical variables were analyzed using Chi-square or Fisher’s exact tests, while continuous independent variables were evaluated using Student’s t-test or Mann-Whitney U test, depending on appropriateness. Adjusted odds ratios were utilized to present the associations between the risk factors and the prevalence of outcomes, specifically anti-HBc and anti-HBs results, while controlling for certain variables. In the final multivariable analysis model, the following variables were included and controlled for: age, ethnicity, and marital status. Statistical significance was considered at p≤0.05.

Results

Five thousand seven hundred and nine (5709) participants were enrolled in this study in the period between June 1 to July 22, 2021. Not all questions in the questionnaire were completed by the study participants.  Thus, the demographics, risk factor and behavior total numbers do not add up to the participant total of 5709.

The average age of the participants engaged into the study was 35.69±10.57 year. The average age of participants with positive anti-HBc was 41.75±9.54, which may be related to the anti-HBV compulsory vaccination that started in 1998.

Most participants were of Kazakh nationality (84%), mainly having secondary education (68%), married (58.8%), non-smokers (75.7%) and denied alcohol consumption on the questionnaire (71.2%).

Regarding nutrition of donors, the main meal was lunch (54.0%), most often the participants prefer to eat 3 or more times a day (90.7%), having fruits and vegetables every day (68.4%) and for the majority (48.0%) meat and meat products were essential parts of the diet.

Among participants, a notable proportion (15.3%) had surgical interventions (including cosmetic surgery or organ removal). A total of 5.2% of the participants reported receiving intravenous or intramuscular treatments such as injections, acupuncture, tattoos, or piercings within the previous 4 months.

When compared to participants with anti-HBc negative results, those positive for anti-HBc were found to be smokers (27.9% vs. 24.3%, p≤0.05), had a longer smoking history (13.6±9.5 years vs. 9.8±8.5 years, p<0.001), had a history of cholesterol problems (6.2% vs 3.9%, p≤0.05), and their main meal was dinner (17.0% vs 14.2%, p≤0.05) (Table 1).

Table 1: Risk factors and anti-HB core positive data.

*Number (percent) of participants missing answer for gender – 20 (9.5%); missing answer for ethnicity – 20 (9.5%); missing answer for education level – 56 (26.5%); missing answer for marital status – 63 (29.9%); missing answer for smoking–46 (21.8%); missing answer for alcohol consumption – 48 (22.7%); missing answer for main meal – 53 (25.1%); missing answer for meals per day – 46 (21.8%); missing answer for eating vegetables and fruits – 59 (28%); missing answer for the percentage of food with meat and meat products – 54 (25.6%); missing answer for having cholesterol disorder – 77 (36.5%); missing answer for family history of hepatitis – 46 (21.8%); missing answer for blood transfusions – 44 (20.9%); missing answer for Intravenous or intramuscular injections, acupuncture, tattoos or piercings – 45 (21.3%); missing answer for surgical interventions – 44 (20.9%);

Results demonstrated that those who have secondary education level (70.1%) were more likely to be anti-HBs-positive (p≤0.05) than other groups, which consist to majority of screened individuals. No difference in anti-HBs prevalence was observed for other risk factors (Table 2).

Table 2: Risk factors and anti-HBs positive data.

*Number (percent) of participants missing answer for gender – 20 (9.5%); missing answer for ethnicity – 20 (9.5%); missing answer for education level – 56 (26.5%); missing answer for marital status – 63 (29.9%); missing answer for smoking–46 (21.8%); missing answer for alcohol consumption – 48 (22.7%); missing answer for main meal – 53 (25.1%); missing answer for meals per day – 46 (21.8%); missing answer for eating vegetables and fruits – 59 (28%); missing answer for the percentage of food with meat and meat products – 54 (25.6%); missing answer for having cholesterol disorder – 77 (36.5%); missing answer for family history of hepatitis – 46 (21.8%); missing answer for blood transfusions – 44 (20.9%); missing answer for Intravenous or intramuscular injections, acupuncture, tattoos or piercings – 45 (21.3%); missing answer for surgical interventions – 44 (20.9%); missing answer for ALT level – 106 (50.2%).

It was also showed that age (p<0.001), ethnicity (p<0.05), marital status (p<0.05) were statistically associated with anti-HBc positivity from descriptive analysis (Table 3). Statistical analysis done to compare gender, nationality, education, marital status, family history of hepatitis, blood transfusion history, injections, or surgical interventions, with a one-year increase in age (adjOR=1.06, 95%CI:1.05-1.07), showed a 6% growth in odds for anti-HBc positivity. Blood donors with Russian ethnicity (adjOR=0.65, 95%CI:0.460.93) and representatives of other nationality (adjOR=0.56, 95%CI:0.37-0.85) were found to have lower odds with positive anti-HBc results when compared to Kazakhs. Among participants that indicated not married, the odds ratio of positive anti-HBc results were lower by 29% (adjOR = 0.71, 95%CI:0.57-0.89) compared to married participants when adjusting for other variables.

Analysis adjusting for gender, nationality, education, marital status, family history of hepatitis, blood transfusions, injections and surgery, showed that those who represented other nationality groups (adjOR=0.36, 95%CI:0.18-0.72) had lower odds of having anti-HBs comparing to the Kazakhs. Those reporting to have Vocational level of education had 50% lower odds of having anti-HBs than those who had a Secondary level (adjOR=0.50, 95%CI:0.28-0.89) (Table 3).

Table 3: Risk factors for anti-HBcore and anti-HBs positivity: Multivariable logistic regression analysis.