Prevalence of Hepatitis B Surface Antigen and Antibody among Health Care Employees in Negri Sembilan, Malaysia, 1989
Abstract
This study was based on a hepatitis B screeningp r o w conducted €none of the states in Malaysia in 1989. The majority (W.6Vo) of the 2986 health employees were screened. One quarter (25%) was found to have serological markers for the Hepatitis B Virus (HBV); 2.1Vo had Hepatitis B surface Antigen (HBsAg) and 22.8% had antibody to the Hepatitis B surface Anti-
gen(anti-HBs).TbeoccnrrenceofHB-
sAg was higher in ethnic Chinese (63Vo) compared to Malays (1.8%) and Indians (09%), even when analyzed by sex, but not with age, type of institution aod geographical locality. The distribution of anti-HBs was higher with ethnic Chinese (41.6%), male sex (27.2%)and age. There was a wide variation of the prevalence of serological markers among occupations and increased relative risksof HBsAg were found among medical assistants (RR 3.7; 95Yo CI 1.4-9.1) and laboratory staff (RR 3.2; 95% CI 1-88), and that of anti-HBs among medical assistants (RR 2.8; 95%CI 1.8-3.7). The variations of HBsAg among oceopations by type of institutions was marginal while that of anti-HBs was higher among attendants and midwives in hospitals, medical assistants in health departments, and assistant nurses and dentists in dental centers. The patterns of distribution of serolw gical markers of HBV among health staffreflectthe situationiu the community with high endemicity and resemble specific occupational factors noted in previons studies in the West. Asia Pac J Public Health 199211993; 6(3): 134- 9.
TC‘I’an,* MBBS, MFOM (London) M Vadivale,+ MBBS, MSc (OM) CN Ong,k PhD *Department of Community, Occupational & Family Medicine National University ofsingapore +Ministryof Health, Malaysia
Introduction
Key roords: Anti- H B s, H BsAg , health care worker, Malaysia, occupation.
for reprints: Dr TC Tan, Department of Community, Occupational & FamiJy Medicine National University of Singapore, National Univnsity Hospital, Lower Kent Ridge Road, Singapore 05 11. Fax:
Ad&
65-779-1489.
The global problem of Hepatitis B Virus (HBV) infection has long been recognized by the World Health Organization (WHO)’. HBV infection has a world-wide distribution and has been found even in remote and isolated communities2. The prevalence of HBV infection among communities variesgreatlyand has beenassociated with geographical factors as well as a complex mix of behavioral, environmental and host factors3. In 1983, WHO initiated the application of preventive programs in countries in which HBV infection is a public health problem4. However, WHO also recognized that any “strategies for immunization must take into consideration the different epidemiological patterns ofhepatitis infection” and the single most important index to delineate the epidemiological pattern must be obtained by population surveys of serological markers of HBV. A detailed review described the situation of sero-epidemiology of Hepatitis B (and A) in the Asia-Pacific region’ covering various population groups including blood donors, hospital patients, prisoners, rural villages, aborigines, children, students, migrants and pregnant women.
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Immunization programs against HBV have already been initiated in several Asian countries including Korea, China, Hong Kong, Thailand, Taiwan, Singapore’ and, lately in 1989, in Malaysia. HBV infection among health care workers has been reported to be higher when compared with nonhospital populations6”. Most of these studies, however, were conducted in Caucasian populations in the West*-” and New Zealand13. This study describes the HBV situation among health care workers in a state in Western Peninsular Malaysia. Hepatitis B immunization in Malaysia was introduced in 1989 with the prime objects of progressively increasing the reservoir of the HBV-resistant population, t h u s reducing the incidence of HBV infection and thereby preventing the longterm sequelae ofprimary liver cancer, liver cirrhosis and chronic liver i n f ~ c t i o n ’Among ~. the groups identified for immunization were high-risk categories of medical and health employees. Materials and Methods Hepatitis B immunization was offered to all health care employees of the Ministry of Health in 1989 in
Asia-Pacific Journal of Public Health 199211993 Vol. 6 No. 3 Peninsular Malaysia. Blood samples were obtained from participants and screened for the Hepatitis B surface antigen (HBsAg) and for antibody to the surface antigen (anti-HBs). Employees found to be seronegative for both markers were subsequently vaccinated. This study was conducted in the State of Negri Sembilan. The institut i o n s surveyed included all government-run hospitals, health departments and dental centers in the State. Personal particulars and service information of individual staff were provided by the Ministry of Health14. Blood samples were analyzed in the Government's Central Laboratory under the supervision of the State Pathologist. HBsAg was analyzed using the AUSAB EIA-ELISA method and anti-HBs with the AUSZYME monoclonal ELISA method. A total of 2986 employees were identified for the survey. Of these, 432 refused screening, thus giving a screening rate of 85.5%. Among the respondents were seven expatriate staff and 22 office-based employees. These were excluded, leaving 84.6% or 2525 respondents for the study. The proportions of HBV serological markers were analyzed by sex, age, ethnicity, type of institution, occupation and locality of work. Blood results and information of respondents were coded and processed with the Dbase 3 and Lotus programs. Chisquare tests were applied for comparing proportions between groups and the Students' t-tests for comparing mean values between groups with the Ep istat program.
Results The overall response to the survey was 84.6% (2525 out of 2986 employees) and comprised 96.8% of 217 dental staff, 89.1% of 567 health staff, and 82.5% of 2202 hospital staff. Among occupational categories, responses ranged from the highest of 97.4% among medical assistants to the lowest of 78.7% among doctors. About three-quarters (72.8%) of the respondents were female. The mean age was 36.8 years (2SD 6.9) with little difference between males (38.9, 2SD 7.7) and females (36.0,
2SD6.4).TheMalaysformed thelargest ethnic group (71.8%), followed by the Indians (16.8%) and the Chinese (1 1.4%). There was little age difference between the three ethnic groups: the mean for Malays was 36.5 years (2SD 6.8), 37.1 (2SD 7.1) for Indians and 38.4 (2SD 7.3) for Chinese. One-quarter (25%) of the subjects had serological markers for HBV; 2.1% had HBsAg and 22.8% had anti-HBs. The prevalence of HBsAg was not related with age, sex, type of institution and locality, while that ofanti-HBs wasnot related to the type of institution and locality. However, the prevalence of anti-HBs was found to be higher in males (27.2%) than females (21.2%) (p < 0.001) and increased with age from 16.9% for the 20-29 year group to 32.9% for the 50-59 year group ( p < 0.001, Table 1). As shown in Table 1, the prevalence of HBsAg was highest in the Chinese (6.3%), followed by the Malays (1.8%), and the Indians (0.9%) (p < 0.001). This trend among the ethnic groups was also found for the distribution ofanti-HBs and for both serological markers (p < 0.001) and remained when male and female subjects were considered separately (Table 2). When analyzed by occupations, the prevalence of HBsAg was highest among medical assistants (5.5%) and laboratory personnel (4.8%),and both occupations showed significant higher relative risk in excess of 3 when compared with attendants (Table 3). For anti-HBs, occupations with higher prevalence and relative risks were found among the dentists (53.1%, R K z 2 . 7 6 , 95% CI 1.83-3.74), medical assistants (28.8%, RR = 1.5,95% CI 1.1-1.99), staff nurses (26.9%, RR = 1.4,95% CI 1.15-1.7) and in midwives and doctors (both 25.3% and RR = 1.3, 95% CI 1-1.8) whcncomparedwithattendants. Table 4 shows the prevalence of serological markers by occupations and the type of institution. The distribution of HBsAg among occupations was unrelated to the type of institution. On the other hand, the presence of anti-HBs was significantly in-
creased among attendants and midwives in hospitals, medical attendants in health departments, and assistant nurses and dentists in dental centers. The risk of having serological markers was higher in employees with frequent contact with blood and blood products than those with occasional contact in the hospitals (26.9% to22.6%,RR= 1.2,95%CI 1-1.4)as well as in the health departments (24.5% to 13.7%, RR = 1.8, 95% CI 1-3.5). There was no evidence of increase in prevalence of and relative risk to serological markers for HBV by frequency of patient contact in both the hospitals (25.6% to 24.7%, RR = 1, 95% CI 0.7-1.6) and health d e p a r t m e n t s (22.9% t o 25%, RR = 0.9,95% CI 0.5-2.7).
Discussion The prevalence ofserological markers among health care workers in this survey reflected the prevalence found in the local community where the prevalence has been reported as 2-8% for HBsAg and 20-25% for anti-HBs5*'5-'7. Consistent with earlier studies, the prevalence of anti-HBs among' health workers increased with, This pattern resembled the occurrence in the Malaysian community where infection was noted to be highest in the first and second decades ~ f l i f e ' ~and - ' ~the mean age of infection was 15 years2'. However, there was no definite relationshipof HBsAg prevalence with age among health workers in our study. Two major patterns of HBV infection have been recogni~ed~.'~. In high prevalenceareas, as in thecaseof Malaysia, infection is acquired early in life and the carrier rate declines or remains the same with age. In low prevalence areas, however, most infections are found among high-risk groups of individuals where there is increased contact with blood and blood products, intravenous users and promiscuous homosexuals3. Several studies in Thailand, Hong Kong and Singapore have shown no overall increase in serological markers among hospital employees when compared with their respective blood donor p o p ~ l a t i o n s ~ ~ ' ~ * ~ ' .
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Table 1. Distribution of IIBV serological markers among health care workers by selected variables Proportion found positive (%) for
No. of subjects
HBsAg
anti-HBs
Both markers
296 1464 598 167
2 2 2.5 2.4
16.9 21.3 26.6 32.9
18.9 23.3 29.1 35.3
Male Female
687 1838
3.1 1.8
Race Malay Chinese Indian
1814 286 425
1.8 6.3 0.9
Locality Urban Rural
1533 992
2.3 1.8
Institution Hospital Health Dental center
1810 505 210
2.3 1.6 2.4
Total
2525
2.1
Age (years) 20-29 30-39 40-49 50-59
NS
p c 0.001
p c 0.00 1
Sex
NS
p c 0.001
NS
NS
27.2 21.2 20.7 41.6 19.1
p c 0.001
p < 0.001
23.3 22.1
NS
23.3 21.4 22.4
NS
22.8
30.3 23 22.5 47.9 20 25.6 23.9 25.5 23 24.8
p c 0.001
p < 0.001
NS
NS
25
Table 2. Prevalence of IIBV markers by ethnicity and sex Proportion ofsubjccts positive (%) for No. of subjects
HBsAg
anti-HBs
Both markers
Female Malay Chinese Indian
1838 1322 235 28 1
1.8 I .4 5.5 0.4
21.2 18.3 42.1 17.1
23 19.7 47.7 17.4
Male Malay Chinese Indian
687 492 51 144
3. I 2.6 9.8 2.1
2525
2.1
Total
This was also the case in the present study when compared with the donor population described by Brown’. The prevalence of serological markers for HBV in health care workers in the West have been reported to be much lower than the findings in this study, with the prevalence of HBsAg ranging from 0.5 to 1.0% and
p < 0.001
p c 0.01
27.2 21.2 39.2 22.9
p < 0.001
NS
22.8
anti-HBs from 6 to 21.9%8-’3*22-23. So far, there was only one report which showed similar high prevalence of serological evidence of past and present HBV infection ranging from 10 to 30%24. The findings of the present study are similar to earlier studies in several countries where HBV infection
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30.3 30.3 49 25
p c 0.001
p c 0.05
25
among health care workers is higher. This increase is related to the male sex15~19,25, foreign-born staff26, nonwhites of Asian place of birth2’ and especially to those of Chinese s t o ~ k ~ ~. -T”h e* ~ vulner~ ability ofthe Chinese (occurring to the same degree in both sexes) to HBV infection found in this study and
Asia-Pacific Journal of Public Health 199211993 Vol. 6 No. 3 Table 3. Seroprevalenceand relative risk of HBV markers by occupations
HBsAG Occupation
anti-HBs
No. of subjects
%positive
RR (95% CI)
%positive
RK (95% CI)
739 484 62 1 I46 162 82 154 32 105
1.5 1.7 2.4
1 1.1 (0.4-2.8)
2.5 2.4 0.6 0 4.8
19.2 18.4 26.9 28.8 25.3 22 25.3 53.1 20
I 1 (0.8-1.2) 1.4(1.2-1.7) 1.5 ( 1.1-2) 1.3 ( 1-1.8) 1.1 (0.7-1.7) 1.3 (1 -1.8) 2.8 (1.8-3.7) 1 (0.7-1.5)
2525
2.1
Attendant Asst. nurse Staff nurse Med. assistant Midwife Community nurse Doctor Dentist Lab personnel Total
1.6 (0.8-3.6) 3.7 (1.4-9.1) 1.7 (0.5-5) 1.6 (0.2-6.4) 0.4 (0.7-2.5)
5.5
-
3.2 (1-8.8)
22.8
Table 4. Preyalence of IIBV markers by occupation and institution
No. of subjxts
All institutions
Hospital
Health
Dental
2525
1810
505
210
2. I
2.3
1.5
1.5
1.7 2.4 5.5 4.8 2.4 0.610
2.4 2.3 6.3 3.4 2.7 0.8
1.6 0 0 1.3 2.9 12.5 2.3 0
2.4 2.7 0 4.8
p value
HBsAg
%positive Attendant Asst. nurse Staff nurse Med. assistant Lab. personnel Midwife Doctor/Dentist
-
0
anti-HBs %positive Attendant Asst. nurse Staff nurse Med. assistant Lab. personnel Midwife Doctor/Dentist
22.8 19.2 18.4 26.9 28.8 20 25.3 25.3153.1
23.3 21.1 16.7 28.1 24.3 21.3 33.3 26.6
21.4 13.7 17.8 29.1 42.9 12.5 18.4 19.2
22.4 9.5 33.3 14.5
Both markers %positive Attendant Asst. nurse Staff nurse Med. assistant Lab. personnel Midwife DoctorlDentist
25 20.7 20 29.3 34.2 24.8 27.8 26153.1
25.5 22.6 19.1 30.4 30.6 24.7 36 27.3
23 13.7 17.8 30.4 45.7 25 20.7 19.2
24.8 12.2 33.3 19.4
several population-based studies in M a l a y ~ i a ~ * ' ~have - ' ' been explained asageneticalpredisposition toantigenic persistence2'.
-
NS NS NS NS NS NS NS NS NS 0.025 0.032
-
0.057
-
-
53.1
0.045 0.0058
-
-
NS 0.033
-
-
-
-
53.1
0.046 0.0072
-
The importance of birthplace, together with the ethnicity and occupation of health care workers have been independently incriminated in
the developing of HBV markers2'. Thetypeofoccupationsfoundtobeat risk were similar to those from earlier studies24 and included staff nurses, laboratory stafp and medical assistants or junior medical staff24. The highest carrier rate of HBsAg was found among staff in the Accident and Emergency (A & E) units (6.6% of 121 employees) and l a b o r a t o r y s t a f f (4.3% of 9 4 employee^)^'^^^. The increased risk among certain occupations in the health industry has been attributed to the degree of exposure to blood and blood products rather than to patient contact8.10,26,32,33
As in previous studies, ruralbased health care workers have lower serological markers to HBV (though not found to be significant in this study) when compared to urbanbased w o r k e r ~ ~ ~There ? ~ ' . were few variations of HBV serological markers between the three types of institutions. However, there wereseveral occupations where the anti-HBs was found to be increased and these were particularly in attendants and midwives in hospitals,.medical assistants in health departments, and assistant nurses and dentists (when compared to doctors) in dental centers. The findings ofthis study suggest that the occupational risk of HBV infection t o health care workers is minimal or marginal in anygeographical area where HBV infection is endemic. This has been explained by the high community exposure to HBV because of the already substantial size of
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.8. immunized subjects and the increased contact with infected individuals outside the health establishment~~~. The limitations of the study de9. pend very much on the nature of the study in that this was based on a Ministry of Health initiated program and much of the information obtained was from service data. Gaps of information found tobeimportant inother 10. studies but unavailable in this study include duration of ~ m p l o y m e n t ~ ~ , previous occupational history, needlestick injury and past hepatitis 11. infection and blood transfusion. Advanced facilities for hemodialysis and renal transplant units found to be important in the West6s38s39 were nonexistent. At the time of writing, the 12. results ofthe vaccination of seronegative subjects and seroconversion information were not available.
Acknowledgements The authors would like to thank the Director and Deputy Director of Health and Medical Services of Negri Sembilan State fortheir permission to use the information for this study and to the Senior Medical Laboratory Technologist of the Blood Bank of Seremban General Hospital for his assistance.
13. 14.
15.
16.
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Abstract
This study was based on a hepatitis B screeningp r o w conducted €none of the states in Malaysia in 1989. The majority (W.6Vo) of the 2986 health employees were screened. One quarter (25%) was found to have serological markers for the Hepatitis B Virus (HBV); 2.1Vo had Hepatitis B surface Antigen (HBsAg) and 22.8% had antibody to the Hepatitis B surface Anti-
gen(anti-HBs).TbeoccnrrenceofHB-
sAg was higher in ethnic Chinese (63Vo) compared to Malays (1.8%) and Indians (09%), even when analyzed by sex, but not with age, type of institution aod geographical locality. The distribution of anti-HBs was higher with ethnic Chinese (41.6%), male sex (27.2%)and age. There was a wide variation of the prevalence of serological markers among occupations and increased relative risksof HBsAg were found among medical assistants (RR 3.7; 95Yo CI 1.4-9.1) and laboratory staff (RR 3.2; 95% CI 1-88), and that of anti-HBs among medical assistants (RR 2.8; 95%CI 1.8-3.7). The variations of HBsAg among oceopations by type of institutions was marginal while that of anti-HBs was higher among attendants and midwives in hospitals, medical assistants in health departments, and assistant nurses and dentists in dental centers. The patterns of distribution of serolw gical markers of HBV among health staffreflectthe situationiu the community with high endemicity and resemble specific occupational factors noted in previons studies in the West. Asia Pac J Public Health 199211993; 6(3): 134- 9.
TC‘I’an,* MBBS, MFOM (London) M Vadivale,+ MBBS, MSc (OM) CN Ong,k PhD *Department of Community, Occupational & Family Medicine National University ofsingapore +Ministryof Health, Malaysia
Introduction
Key roords: Anti- H B s, H BsAg , health care worker, Malaysia, occupation.
for reprints: Dr TC Tan, Department of Community, Occupational & FamiJy Medicine National University of Singapore, National Univnsity Hospital, Lower Kent Ridge Road, Singapore 05 11. Fax:
Ad&
65-779-1489.
The global problem of Hepatitis B Virus (HBV) infection has long been recognized by the World Health Organization (WHO)’. HBV infection has a world-wide distribution and has been found even in remote and isolated communities2. The prevalence of HBV infection among communities variesgreatlyand has beenassociated with geographical factors as well as a complex mix of behavioral, environmental and host factors3. In 1983, WHO initiated the application of preventive programs in countries in which HBV infection is a public health problem4. However, WHO also recognized that any “strategies for immunization must take into consideration the different epidemiological patterns ofhepatitis infection” and the single most important index to delineate the epidemiological pattern must be obtained by population surveys of serological markers of HBV. A detailed review described the situation of sero-epidemiology of Hepatitis B (and A) in the Asia-Pacific region’ covering various population groups including blood donors, hospital patients, prisoners, rural villages, aborigines, children, students, migrants and pregnant women.
t34
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Immunization programs against HBV have already been initiated in several Asian countries including Korea, China, Hong Kong, Thailand, Taiwan, Singapore’ and, lately in 1989, in Malaysia. HBV infection among health care workers has been reported to be higher when compared with nonhospital populations6”. Most of these studies, however, were conducted in Caucasian populations in the West*-” and New Zealand13. This study describes the HBV situation among health care workers in a state in Western Peninsular Malaysia. Hepatitis B immunization in Malaysia was introduced in 1989 with the prime objects of progressively increasing the reservoir of the HBV-resistant population, t h u s reducing the incidence of HBV infection and thereby preventing the longterm sequelae ofprimary liver cancer, liver cirrhosis and chronic liver i n f ~ c t i o n ’Among ~. the groups identified for immunization were high-risk categories of medical and health employees. Materials and Methods Hepatitis B immunization was offered to all health care employees of the Ministry of Health in 1989 in
Asia-Pacific Journal of Public Health 199211993 Vol. 6 No. 3 Peninsular Malaysia. Blood samples were obtained from participants and screened for the Hepatitis B surface antigen (HBsAg) and for antibody to the surface antigen (anti-HBs). Employees found to be seronegative for both markers were subsequently vaccinated. This study was conducted in the State of Negri Sembilan. The institut i o n s surveyed included all government-run hospitals, health departments and dental centers in the State. Personal particulars and service information of individual staff were provided by the Ministry of Health14. Blood samples were analyzed in the Government's Central Laboratory under the supervision of the State Pathologist. HBsAg was analyzed using the AUSAB EIA-ELISA method and anti-HBs with the AUSZYME monoclonal ELISA method. A total of 2986 employees were identified for the survey. Of these, 432 refused screening, thus giving a screening rate of 85.5%. Among the respondents were seven expatriate staff and 22 office-based employees. These were excluded, leaving 84.6% or 2525 respondents for the study. The proportions of HBV serological markers were analyzed by sex, age, ethnicity, type of institution, occupation and locality of work. Blood results and information of respondents were coded and processed with the Dbase 3 and Lotus programs. Chisquare tests were applied for comparing proportions between groups and the Students' t-tests for comparing mean values between groups with the Ep istat program.
Results The overall response to the survey was 84.6% (2525 out of 2986 employees) and comprised 96.8% of 217 dental staff, 89.1% of 567 health staff, and 82.5% of 2202 hospital staff. Among occupational categories, responses ranged from the highest of 97.4% among medical assistants to the lowest of 78.7% among doctors. About three-quarters (72.8%) of the respondents were female. The mean age was 36.8 years (2SD 6.9) with little difference between males (38.9, 2SD 7.7) and females (36.0,
2SD6.4).TheMalaysformed thelargest ethnic group (71.8%), followed by the Indians (16.8%) and the Chinese (1 1.4%). There was little age difference between the three ethnic groups: the mean for Malays was 36.5 years (2SD 6.8), 37.1 (2SD 7.1) for Indians and 38.4 (2SD 7.3) for Chinese. One-quarter (25%) of the subjects had serological markers for HBV; 2.1% had HBsAg and 22.8% had anti-HBs. The prevalence of HBsAg was not related with age, sex, type of institution and locality, while that ofanti-HBs wasnot related to the type of institution and locality. However, the prevalence of anti-HBs was found to be higher in males (27.2%) than females (21.2%) (p < 0.001) and increased with age from 16.9% for the 20-29 year group to 32.9% for the 50-59 year group ( p < 0.001, Table 1). As shown in Table 1, the prevalence of HBsAg was highest in the Chinese (6.3%), followed by the Malays (1.8%), and the Indians (0.9%) (p < 0.001). This trend among the ethnic groups was also found for the distribution ofanti-HBs and for both serological markers (p < 0.001) and remained when male and female subjects were considered separately (Table 2). When analyzed by occupations, the prevalence of HBsAg was highest among medical assistants (5.5%) and laboratory personnel (4.8%),and both occupations showed significant higher relative risk in excess of 3 when compared with attendants (Table 3). For anti-HBs, occupations with higher prevalence and relative risks were found among the dentists (53.1%, R K z 2 . 7 6 , 95% CI 1.83-3.74), medical assistants (28.8%, RR = 1.5,95% CI 1.1-1.99), staff nurses (26.9%, RR = 1.4,95% CI 1.15-1.7) and in midwives and doctors (both 25.3% and RR = 1.3, 95% CI 1-1.8) whcncomparedwithattendants. Table 4 shows the prevalence of serological markers by occupations and the type of institution. The distribution of HBsAg among occupations was unrelated to the type of institution. On the other hand, the presence of anti-HBs was significantly in-
creased among attendants and midwives in hospitals, medical attendants in health departments, and assistant nurses and dentists in dental centers. The risk of having serological markers was higher in employees with frequent contact with blood and blood products than those with occasional contact in the hospitals (26.9% to22.6%,RR= 1.2,95%CI 1-1.4)as well as in the health departments (24.5% to 13.7%, RR = 1.8, 95% CI 1-3.5). There was no evidence of increase in prevalence of and relative risk to serological markers for HBV by frequency of patient contact in both the hospitals (25.6% to 24.7%, RR = 1, 95% CI 0.7-1.6) and health d e p a r t m e n t s (22.9% t o 25%, RR = 0.9,95% CI 0.5-2.7).
Discussion The prevalence ofserological markers among health care workers in this survey reflected the prevalence found in the local community where the prevalence has been reported as 2-8% for HBsAg and 20-25% for anti-HBs5*'5-'7. Consistent with earlier studies, the prevalence of anti-HBs among' health workers increased with, This pattern resembled the occurrence in the Malaysian community where infection was noted to be highest in the first and second decades ~ f l i f e ' ~and - ' ~the mean age of infection was 15 years2'. However, there was no definite relationshipof HBsAg prevalence with age among health workers in our study. Two major patterns of HBV infection have been recogni~ed~.'~. In high prevalenceareas, as in thecaseof Malaysia, infection is acquired early in life and the carrier rate declines or remains the same with age. In low prevalence areas, however, most infections are found among high-risk groups of individuals where there is increased contact with blood and blood products, intravenous users and promiscuous homosexuals3. Several studies in Thailand, Hong Kong and Singapore have shown no overall increase in serological markers among hospital employees when compared with their respective blood donor p o p ~ l a t i o n s ~ ~ ' ~ * ~ ' .
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Table 1. Distribution of IIBV serological markers among health care workers by selected variables Proportion found positive (%) for
No. of subjects
HBsAg
anti-HBs
Both markers
296 1464 598 167
2 2 2.5 2.4
16.9 21.3 26.6 32.9
18.9 23.3 29.1 35.3
Male Female
687 1838
3.1 1.8
Race Malay Chinese Indian
1814 286 425
1.8 6.3 0.9
Locality Urban Rural
1533 992
2.3 1.8
Institution Hospital Health Dental center
1810 505 210
2.3 1.6 2.4
Total
2525
2.1
Age (years) 20-29 30-39 40-49 50-59
NS
p c 0.001
p c 0.00 1
Sex
NS
p c 0.001
NS
NS
27.2 21.2 20.7 41.6 19.1
p c 0.001
p < 0.001
23.3 22.1
NS
23.3 21.4 22.4
NS
22.8
30.3 23 22.5 47.9 20 25.6 23.9 25.5 23 24.8
p c 0.001
p < 0.001
NS
NS
25
Table 2. Prevalence of IIBV markers by ethnicity and sex Proportion ofsubjccts positive (%) for No. of subjects
HBsAg
anti-HBs
Both markers
Female Malay Chinese Indian
1838 1322 235 28 1
1.8 I .4 5.5 0.4
21.2 18.3 42.1 17.1
23 19.7 47.7 17.4
Male Malay Chinese Indian
687 492 51 144
3. I 2.6 9.8 2.1
2525
2.1
Total
This was also the case in the present study when compared with the donor population described by Brown’. The prevalence of serological markers for HBV in health care workers in the West have been reported to be much lower than the findings in this study, with the prevalence of HBsAg ranging from 0.5 to 1.0% and
p < 0.001
p c 0.01
27.2 21.2 39.2 22.9
p < 0.001
NS
22.8
anti-HBs from 6 to 21.9%8-’3*22-23. So far, there was only one report which showed similar high prevalence of serological evidence of past and present HBV infection ranging from 10 to 30%24. The findings of the present study are similar to earlier studies in several countries where HBV infection
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30.3 30.3 49 25
p c 0.001
p c 0.05
25
among health care workers is higher. This increase is related to the male sex15~19,25, foreign-born staff26, nonwhites of Asian place of birth2’ and especially to those of Chinese s t o ~ k ~ ~. -T”h e* ~ vulner~ ability ofthe Chinese (occurring to the same degree in both sexes) to HBV infection found in this study and
Asia-Pacific Journal of Public Health 199211993 Vol. 6 No. 3 Table 3. Seroprevalenceand relative risk of HBV markers by occupations
HBsAG Occupation
anti-HBs
No. of subjects
%positive
RR (95% CI)
%positive
RK (95% CI)
739 484 62 1 I46 162 82 154 32 105
1.5 1.7 2.4
1 1.1 (0.4-2.8)
2.5 2.4 0.6 0 4.8
19.2 18.4 26.9 28.8 25.3 22 25.3 53.1 20
I 1 (0.8-1.2) 1.4(1.2-1.7) 1.5 ( 1.1-2) 1.3 ( 1-1.8) 1.1 (0.7-1.7) 1.3 (1 -1.8) 2.8 (1.8-3.7) 1 (0.7-1.5)
2525
2.1
Attendant Asst. nurse Staff nurse Med. assistant Midwife Community nurse Doctor Dentist Lab personnel Total
1.6 (0.8-3.6) 3.7 (1.4-9.1) 1.7 (0.5-5) 1.6 (0.2-6.4) 0.4 (0.7-2.5)
5.5
-
3.2 (1-8.8)
22.8
Table 4. Preyalence of IIBV markers by occupation and institution
No. of subjxts
All institutions
Hospital
Health
Dental
2525
1810
505
210
2. I
2.3
1.5
1.5
1.7 2.4 5.5 4.8 2.4 0.610
2.4 2.3 6.3 3.4 2.7 0.8
1.6 0 0 1.3 2.9 12.5 2.3 0
2.4 2.7 0 4.8
p value
HBsAg
%positive Attendant Asst. nurse Staff nurse Med. assistant Lab. personnel Midwife Doctor/Dentist
-
0
anti-HBs %positive Attendant Asst. nurse Staff nurse Med. assistant Lab. personnel Midwife Doctor/Dentist
22.8 19.2 18.4 26.9 28.8 20 25.3 25.3153.1
23.3 21.1 16.7 28.1 24.3 21.3 33.3 26.6
21.4 13.7 17.8 29.1 42.9 12.5 18.4 19.2
22.4 9.5 33.3 14.5
Both markers %positive Attendant Asst. nurse Staff nurse Med. assistant Lab. personnel Midwife DoctorlDentist
25 20.7 20 29.3 34.2 24.8 27.8 26153.1
25.5 22.6 19.1 30.4 30.6 24.7 36 27.3
23 13.7 17.8 30.4 45.7 25 20.7 19.2
24.8 12.2 33.3 19.4
several population-based studies in M a l a y ~ i a ~ * ' ~have - ' ' been explained asageneticalpredisposition toantigenic persistence2'.
-
NS NS NS NS NS NS NS NS NS 0.025 0.032
-
0.057
-
-
53.1
0.045 0.0058
-
-
NS 0.033
-
-
-
-
53.1
0.046 0.0072
-
The importance of birthplace, together with the ethnicity and occupation of health care workers have been independently incriminated in
the developing of HBV markers2'. Thetypeofoccupationsfoundtobeat risk were similar to those from earlier studies24 and included staff nurses, laboratory stafp and medical assistants or junior medical staff24. The highest carrier rate of HBsAg was found among staff in the Accident and Emergency (A & E) units (6.6% of 121 employees) and l a b o r a t o r y s t a f f (4.3% of 9 4 employee^)^'^^^. The increased risk among certain occupations in the health industry has been attributed to the degree of exposure to blood and blood products rather than to patient contact8.10,26,32,33
As in previous studies, ruralbased health care workers have lower serological markers to HBV (though not found to be significant in this study) when compared to urbanbased w o r k e r ~ ~ ~There ? ~ ' . were few variations of HBV serological markers between the three types of institutions. However, there wereseveral occupations where the anti-HBs was found to be increased and these were particularly in attendants and midwives in hospitals,.medical assistants in health departments, and assistant nurses and dentists (when compared to doctors) in dental centers. The findings ofthis study suggest that the occupational risk of HBV infection t o health care workers is minimal or marginal in anygeographical area where HBV infection is endemic. This has been explained by the high community exposure to HBV because of the already substantial size of
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.8. immunized subjects and the increased contact with infected individuals outside the health establishment~~~. The limitations of the study de9. pend very much on the nature of the study in that this was based on a Ministry of Health initiated program and much of the information obtained was from service data. Gaps of information found tobeimportant inother 10. studies but unavailable in this study include duration of ~ m p l o y m e n t ~ ~ , previous occupational history, needlestick injury and past hepatitis 11. infection and blood transfusion. Advanced facilities for hemodialysis and renal transplant units found to be important in the West6s38s39 were nonexistent. At the time of writing, the 12. results ofthe vaccination of seronegative subjects and seroconversion information were not available.
Acknowledgements The authors would like to thank the Director and Deputy Director of Health and Medical Services of Negri Sembilan State fortheir permission to use the information for this study and to the Senior Medical Laboratory Technologist of the Blood Bank of Seremban General Hospital for his assistance.
13. 14.
15.
16.
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