SERO-EPIDEMIOLOGIC SURVEY OF HEPATITIS B MARKERS IN NATIONAL IRANIAN OIL COMPANY (NIOC) HEALTH WORKERS IN TEHRAN PRIOR TO MASS VACCINATION

B. Hamidi MD, MPH*; M. Bahadori MD* *, S. Mansouri MD*, R. Nategh MD**

*Department of Infectious Disease, NIOC Hospital, Tehran ** Department of Virology, Tehran University of Medical Sciences, Tehran, Iran

  • Abstract

    Objective-To determine the prevalence of sero-epidemiologic markers of Hepatitis B virus (HBV) in NIOC health organization personnel in Tehran, and to study the risk of exposure of medical staff (who are more exposed to patients and/or blood products.)
    Method-A sero-prevalence study was carried out on 600 subjects with no past history of vaccination against hepatitis B. Of these, 377 were more prone to exposure (high-risk group), and were compared to the rest of the subjects (comparison group) and the normal population.
    Results-A sample of 447 subjects were tested for all markers (HBsAg, HBsAb, and HBcAb), of which 101 (23%) were positive for at least one of the markers (CI95%: 19%-27%). Prevalence of HBsAg, HBsAb, and HBcAb were found to be 1.83% (CI95%: 0.97%-3.36%), 16.11% (CI95%: 13.3%-19.4%), and 17.86% (CI95%: 14.5%-21.8%) respectively. While no significant correlation was found with sex and years of service, significant correlation with age was found for seroprevalence of HBsAb (P<0.01) and HBcAb (P<0.05). No significant sero-prevalence of any marker was found in the high risk group compared to the comparison group in this study and population-based survey results. Significantly increased risk of seropositivity for HBsAg was found among laboratory personnel of laboratory as compared to the comparison group (RR: 8.8, P<0.05, CI95%: 1.4-54.6).
    Discussion-No significant increased risk of exposure based on serologic studies in health care personnel in communities where HBV is endemic, may be attributed to a balanced increased risk of occupational exposure. The reason might be that safe life styles and appropriate job behavior due to higher level of education and socioeconomic factors compared to general population in such communities could result in their equal risk of infection. Further studies are warranted to eliminate the role of socioeconomic status as a possible confounding factor in risk assessment studies for HBV exposure in health care workers.

    Keywords • Hepatitis B • health personnel • occupational diseases • immunization

    •

    Introduction

    It is more than two decades that hepatitis B is considered as an occupational disease among health workers.1-3 Prevalence of HbsAg in developed countries is believed to be around 0.1% to 0.5%. In endemic areas it may rise to 3% to 5%, and in hyperendemic areas up to 30%. Hepatitis B is more prevalent in south Asia and the Far East. Amini and Salehi showed that in Iran it is more prevalent in southeastern regions of the country.

    Farzadegan in 1979 showed that prevalence of HBsAg in Iran is between 2.5% and 7.2%, and 30% for HbcAb7; again more prevalent in southeastern regions of the country.

    In another study by Harbour and Foroozanfar in 1987, the prevalence of HBsAg in volunteer blood donors in Iran turned out to be 1.7%. In a population based study in Hamedan, Iran in 1993 9 seropositivity for any HBV marker was found in 25.72% subjects. Of these 2.49% were carriers of HBsAg, and 18.09% were positive for HbsAb. In another study on 250000 volunteer blood donors in Tehran, 3.6% of men and 1.6% of women turned out to be Australian antigen positive. In this study 37% had HBcAb in their sera.

    A significant body of research reveals high prevalence of hepatitis B markers among medical personnel as compared to the normal population. 12-14 In the U.S., the overall risk of hepatitis B among persons employed in health-related fields is estimated to be approximately four times that of the general adult population. Physicians and dentists are five to ten times more likely than the general adult population to experience hepatitis B infection. Infection rates ten or more times above the average have often been a characteristic of surgeons, patient care personnel in dialysis units and mentally handicapped institutions, and clinical laboratory workers having frequent contacts with blood samples. In a study in India16, although HBsAg prevalence was not significantly increased in preclinical as compared to the clinical subjects, there was a significant increase in the titer of the antibodies in these two groups. In a study in Singapore17, more than 2500 health workers were searched for HBV markers. It was found to be more prevalent in medical assistants and medical laboratory personnel than other health workers. In 1991 seroprevalence of the markers were measured in selected individuals in Philippines18, and was also indicative of high exposure rates in health personnel.

    Similar studies in Iran have also shown an increased prevalence in health personnel. In a study involving selected Ob/Gyn wards in several hospitals in Tehran20, Afshar showed an increased prevalence of HBV markers in health care workers.

    While there is compiling evidence of increased prevalence of HBV markers in health care personnel, there are studies, which show insignificant serologic evidence of increased risk of exposure to this virus in health care workers. A study in Lahore, Pakistan21 and a similar study in Sydney, Australia22 did not indicate any higher risk of exposure to HBV in health care personnel and the markers were more prevalent in the control group as compared to the medical personnel. Some studies on emergency ward and paramedic personnel had also revealed similar results with no increased risk of exposure. 23-25

    Some studies in Iran had similar results. In a study involving 681 subjects working in medical laboratories in Tehran26,Sohrabi showed no significant prevalence of HBV seromarkers in this group. In this study, significant prevalence was demonstrated only in the over 55 years age group and in those having more than 10 years of service in this occupation. In this study, years of service lost its significance when in covariate analysis, role of age was eliminated. It means that years of service as a laboratory worker had not significantly increased the risk of exposure. Mansouri in a study on 725 subjects working in a hospital in Arak27 showed no significant increased risk among high-risk groups relative to the personnel of non-medical departments. Significant prevalence was demonstrated in men and with increasing age. No significant prevalence of sero-markers was shown by Kosari28, Rezvan29, and Rezaei30 either.

    To investigate the prevalence of serologic markers of hepatitis B in personnel of National Iranian Oil Company (NIOC) central hospital in Tehran, and to find the relative risk of exposure with sero-conversion in subjects who were more prone to patients and/or blood products, data from a previous serologic screening on 600 individuals is analyzed.

    Materials & Methods

    Data for this study was gathered from a HBV sero-markers’ study on personnel of NIOC health department and central hospital in 1989 prior to mass vaccination against HBV. Sero-markers study was carried out during a period of one year and sera were reported by National Iranian Blood Organization laboratories for HBsAg, HbsAb, HBcAb using ELISA method. Personal and demographic information was recorded at time of serologic study. Cases with uncertain data and a few individuals with a history HBV vaccination were not included in the study. All "weakly positive" results were considered positive.

    Individuals working in operating rooms (including nurses and service workers), nurses (including service workers), laboratory staff, physicians (surgeons and non-surgeons) and dentists were categorized as the high-risk groups. All other individuals including personnel of managerial and general services, radiology, physiotherapy, and similar units were categorized as the comparison group. Although much care was taken to categorize individuals according to their appropriate occupation (based on duration of the job they were mostly involved in), probable changes in occupation may contribute as a limiting factor in this study.

    All data were fed to computer and summarized tables were prepared and tested for levels of significance and confidence intervals. Relative risk of exposure was determined in high-risk group relative to comparison group, with any positive marker as an indicator of exposure. Three age groups and three groups for years of service were defined.

    Results of the study on Hamedan province 9, were used as population based prevalence rates. Medline was reviewed for related data from 1968 on Internet (PubMed) and results were compared if possible.

    Results

    Twenty three percent of those who were tested for all three markers (HBsAg, HBsAb, and HBcAb) were positive for at least one marker. Eleven out of 600 subjects were positive for HBsAg (prevalence: 1.83%, with Fleiss quadratic 95% confidence interval between 0.97% and 3.36%) (Table 1). Prevalence of HBsAb was 16.11% (Fleiss quadratic 95% CI between 13.30% and 19.36%) and that for HBcAb was 17.86% (95% CI between 14.49% and 21.79%). Although a relative risk of 3.2 was seen in men for a positive HBsAg, it was not significant at the level of 95% confidence.

    Distribution of HBsAg was not different in the three age groups, but significant correlation of HBsAb and HBcAb was found with age (p<0.005 and p<0.05 respectively) (Table 2). No correlation was found between prevalence of either marker with years of service.

    No significant relative risk of exposure was found whether within different jobs in the high-risk group or between the high-risk and the comparison group (Table 3). However, significant relative risk for a positive HBsAg was found in laboratory personnel when compared with the comparison group (RR: 8.8, Fisher exact p<0.05).

    In this study, none of the markers showed significant prevalence amongst the subjects. Even its prevalence in the high risk group was insignificant as compared to the prevalence based on general population studies (Hamedan study 9).

    Discussion

    Results of this study show that as long as HBsAg per se is considered as an indicator for HBV exposure, medical laboratory personnel can be considered at higher risk of exposure even if adjusted for age and years of service or sex. However, none of the other two markers or any marker in an individual shows significant risk of exposure in any group as compared to the comparison group or with the general population. While the findings in this study are consistent with those of Sohrabi26 , Mansouri27, Kosari28, Rezvan29, and Rezaei30 indicating no significantly increased risk of exposure in health care personnel, the prevalence of sero-markers is less than what Afshar20 and Mehrabi19 have shown.

    Significant increased sero-prevalence of HBsAb and HBcAb was demonstrated with increasing age but not with HBsAg. No correlation of exposure to HBV was found with years of service or sex.

    This all implies that at least regions in which hepatitis B is endemic, community exposure to this virus plays a more important role in sero-coversion than occupational risks of exposure. In fact, higher socioeconomic status of graduate individuals in health care occupations as compared to the general population (in almost all countries where hepatitis B is endemic) may play a protective role due to healthier life style in health care personnel. This, of course, does not underestimate the role and necessity of health care personnel to receive vaccination against hepatitis B.

    Further studies are warranted to compensate possible job classification bias of subjects and to eliminate the role of socioeconomic status as a possible confounding factor in risk assessment studies for HBV exposure in health care workers.

    Effects of vaccination against HBV on prevalence of HBsAg in health care personnel in NIOC central hospital may well be subject to further research.

    Acknowledgments

    The authors appreciate the cooperation of Mrs Namazi in charge of the vaccination unit of NIOC hospital for providing the data for this study. Cooperation of Iranian Blood Transfusion Organization is also appreciated.

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