Prevalence of hepatitis B antibodies in hospital personnel W-D. LEERS,f MD,
PH
D,
FRCP[c],
DIP
BACT, CPH; G.M.
KoUROUPIS,J
D SC, M
SC, FRSH, CPH, FRMS
Summary: Of 426 hospital staff tested for hepatitis B surface antibody (anti-HBs) by the radioimmunoassay method 57 (13.4%) had positive results. Laboratory staff had the highest prevalence, followed by nurses, and both values were significantly higher than that of administrative staff. Clerical staff working in laboratories were at the same risk for hepatitis B as general-duty
avec la presence d'anti-HBs. Le risque d'hepatite B est plus eleve chez les membres du personnel hospitalier qui sont en contact direct avec ces malades. II faut cependant noter que le contact avec les malades est moins important que le contact avec le sang ou avec d'autres echantillons de ces malades.
nurses.
The prevalence of hepatitis B surface antibody (anti-HBs) varies widely in different population groups, apparently being about 40% in lower socioeconomic groups and about 50% among drug addicts.1 The prevalence of anti-HBs also varies among patients and hospital personnel. It is well known that the incidence of hepatitis B is higher in patients who have received multiple blood trans¬ fusions,2 and that hepatitis B is a hazard for laboratory personnel handling blood or blood products.3 One study* showed the prevalence of anti-HBs to be 14.4% in volun¬ teer blood donors, 22.6% in commercial blood donors, 14.8% in blood bank personnel, 11.4% in laboratory per¬ sonnel and 82.6% in persons who had received multiple transfusions. A recent study in a hospital population revealed that anti-HBs was twice as frequent among health personnel compared with controls not exposed to blood products.5 A more recent study in Ontario6 determined the following prevalence figures for anti-HBs: staff of renal dialysis unit, 16.0%; staff of institutions for the mentally retarded, 12.5%; and patients of these institutions, 44.3%. We determined the prevalence of anti-HBs in hospital staff by comparing groups at high risk for hepatitis B with those at low risk.
Significantly more staff with anti-HBs had a history of hepatitis (19.3%) compared with staff without anti-HBs (7.9%), and significantly more staff with a history of hepatitis had anti-HBs (25.6%) compared with staff without such a history (12.0%). History of blood transfusions was not related to prevalence of anti-HBg. The risk for hepatitis B is greater in hospital staff who are in direct contact with patients or handle patients' blood and other specimens. However, contact with patients is less important than contact with patients' blood and other specimens. Resume: Sur 426 membres du personnel hospitalier chez lesquels nous avons recherche I'anticorps de surface de I'hepatite B (anti-HBJ par la technique radioimmunologique, 57 (13.4%) donnaient des resultats positifs. Les techniciens de laboratoire etaient les plus touches, suivis des infirmieres, et ces deux valeurs etaient significativement plus elevees que celles trouvees parmi le personnel administratif. Toutefois, les employes administratifs travaillant dans les laboratoires etaient sujets au meme risque d'hepatite B que les infirmieres generales. Un nombre significativement plus eleve de personnes porteurs de l'anti-HBs avaient des antecedents d'hepatite (19.3%) par comparaison avec des personnes sans anti-HBs (7.9%), et un nombre significativement plus eleve de personnes ayant des antecedents d'hepatite avaient des anti-HBs (25.6%) par comparaison avec ies sujets n'ayant pas
ces
antecedents (12.0%). Des transfusions anterieures
Presented at the conjoint annual meeting of the Canadian Association of Medical Microbiologists, Calgary, June 25 to 29, 1975 From the department of medical microbiology, faculty of medicine, University of Toronto, and the department of microbiology, The Wellesley Hospital, Toronto tChief, department of microbiology, The Wellesley Hospital; assistant department of medical microbiology, University of Toronto Virologist, department of microbiology, The Wellesley Hospital Reprint requests to: Dr. W-D. Leers, The Wellesley Hospital, 160 Wellesley St. E, Toronto, ON M4Y 1J3
?rofessor,
844 CMA JOURNAL/NOVEMBER 8, 1975/VOL. 113
n'avaient pas de rapport
Materials and methods
Subjects and blood samples Three risk groups of hospital personnel were defined: the high-risk group consisted of staff having routine direct contact with patients, their blood or secretions, or blood products; the low-risk group consisted of staff having no such direct contact; and the intermediate-risk group con¬ sisted of staff who could not be placed in either the highor the low-risk group. The infection control nurse gave an explanatory letter to each department head and explained the study to the
participants (61 men and 365 women), all of whom volunteers. Every participant completed a question¬ naire about history of hepatitis, blood transfusions and other relevant information. Blood samples were collected by nurses of the intra¬ venous team and sent to our virus laboratory, where the serum was separated and stored at 4°C. Assay for anti-HBs was begun after all 426 samples had arrived.
although the difference was not significant. However, the clerical staff and general-duty nurses had a significantly higher (P = 0.10) prevalence of anti-HBs compared with the administrative personnel. The low-risk group consisted of 23 senior administrators and supervisory personnel and 59 clerical staff. There was no significant difference in the prevalence of anti-HBs between the two groups.
Radioimmunoassay for anti-HBs
Laboratory personnel at high risk The prevalence of anti-HBs among the various types of laboratory personnel is given in Table II. Professional and technical staff are included but clerical staff are omitted because they are considered an intermediate-risk group. There was no significant difference in the prevalence of anti-HBs between clinical chemistry, hematology and micro¬ biology staff, but the prevalence of anti-HBs in the clinical pathology staff was significantly lower (P 0.05) than that in the former three groups. The prevalence in the "other laboratory staff was also significantly lower compared with that of the clinical chemistry and hematology (P 0.05) and microbiology (P 0.10) staff.
426
were
Anti-HBs in serum was detected by the direct solid-phase radioimmunoassay (RIA) technique, which has proven prac¬ tical for assay of anti-HBs.710 We used the Ausab* kit, which contains plastic beads coated with anti-HBs. To a tube containing a coated glass bead was added 0.2 ml of serum; the tube was incubated for 16 to 20 hours at room temperature. If antibody was present it attached to the solid-phase antigen. Then 0.2 ml of hepatitis B surface antigen (HBsAg) tagged with iodine-125 was added. During 4 hours' incubation at room temperature the antigen at¬ tached to the antibody, creating a tagged antigen-antibodyantigen "sandwich". Statistical analysis The chi-square (x2) test was applied for a sample size less than 30 if the smallest expected value was greater than five; if this value was smaller than five the Fisher exact probability test was applied. The test for normal distribu¬ tion was used for a sample size greater than 30. Results There was no significant difference in prevalence of antiHBs between the male and female staff. The prevalence of anti-HBs in the three risk groups is given in Table I. The overall prevalence in the high-risk group differed significantly (P = 0.05) from that in the low-risk group, but the overall prevalence in the intermediate-risk group did not differ significantly from that in either the high- or low-risk group. In the high-risk group the laboratory staff had a signifi¬ cantly higher (P = 0.05) prevalence of anti-HBs compared with the nurses. In the intermediate-risk group the clerical staff of the laboratories and the general-duty nurses had a similar and higher prevalence of anti-HBs than the ward secretaries, *Abbott Laboratories, North Chicago. all technical details.
Accompanying pamphlet provides
=
=
=
Nurses at high risk The prevalence of anti-HBs in nurses in the high-risk group is given in Table III. There was a significant differ¬ ence (P = 0.10) in prevalence between nurses on the intra¬ venous team and nurses in the renal dialysis unit.
Hepatitis and blood transfusions The relation of a history of hepatitis or blood transfu¬ or both, with the presence of anti-HBs is presented in Table IV. Two laboratory technicians and one ward
sions,
Table II.Prevalence of anti-HBs in
laboratory personnel*
?Including physicians, scientists, technologists and laboratory assistants in high-risk groups. disease, medicine, biophysics, respiratory technology. jResearch, rheumatic between this group and first three groups significant at P 0.05. JDifference § Difference between this group and first two groups significant at P 0.05, and between this group and microbiology group, at P 0.10. =
=
Table I.Prevalence of hepatitis B surface in risk groups of hospital staff Total
Group
no.
§ Difference significant at P 0.10. =
antibody (anti-HBJ Anti-HB8-positive no. (and %)
=
Table lll.Prevalence of anti-HBs in
Total
Area or service
?Difference significant at P
nurses no.
=
in
high-risk
areas
Anti-HB8-positive no. (and %)
0.10.
CMA JOURNAL/NOVEMBER 8, 1975/VOL. 113 845
secretary gave a history of both hepatitis and blood trans¬ fusions. A significantly larger (P = 0.05) number of staff with anti-HBs than without had a history of hepatitis, and a significantly larger (P = 0.05) number of staff with antiHBs had a history of hepatitis than of transfusions. There was no significant difference with respect to the history of blood transfusions between staff with and without anti-HBs. A more detailed analysis is presented in Table V. A his¬ tory of hepatitis was given by 24% of the laboratory staff with anti-HBs but by only 9.2% of the laboratory staff without anti-HBs; the difference is significant (P = 0.05). For each of the other groups there was no significant dif¬ ference in the percentage with a history of hepatitis between those with and those without anti-HBs. However, the per¬ centage of all staff with a history of hepatitis and anti-HBs, 19.3, was significantly higher (P = 0.05) than that of all staff with a history of hepatitis but without anti-HBs, 8.7. Also, the percentage of anti-HBs-positive laboratory staff with a history of hepatitis was significantly higher (P = 0.05) than the percentage for the other anti-HBs-positive groups. Of the 43 staff with a history of hepatitis 11 (25.6%) Table IV.Prevalence of anti-HBg in staff with hepatitis or blood transfusion or both
History Hepatitis Transfusions Hepatitis and
Anti-HB8-positive (n 57) no. (and %) no. (and %) 11 (19.3)*t 40(9.4) 31 (7.3) 3(5.3)f 0(0) 3(0.7) 14 (24.6) 74(17.4) Total
transfusions Total ?Difference significant at P fDifference significant at P
= =
=
Anti-HBs-negative (n 369) no. (and %) 29 ( 7.9)* 28 ( 7.6) 3 ( 0.8) 60 (16.3) =
0.05.
Table V.Prevalence of anti-HBs in staff with
.
Discussion Our results confirm that hospital laboratory personnel are at an increased risk for hepatitis B and have a high prevalence of anti-HBs.5 We found no significant difference in prevalence between the sexes. However, the prevalence of anti-HBs in the hospital staff we surveyed (13.4%) was not significantly different from that (14.8%) in 1004 unselected patients whose sera we tested previously (unpublished data). The high-risk group, laboratory staff and nurses having routine direct contact with patients, their blood or secretions, or blood products, had a significantly higher prevalence of anti-HBs (16.5%) than the low-risk group (6.1%), administrative staff having no such direct contact.
Among laboratory staff, the clinical chemistry staff had highest prevalence of HBsAg (40.0%), followed by hematology (32.0%) and microbiology (20.8%) staff. None of the pathology staff, including pathologists, had anti-HBs; pathology technologists usually handle noninfectious, formolized specimens, but the pathologist who performs autop¬ sies is at an increased risk for hepatitis B. The prevalence of anti-HBs in the clinical chemistry, hematology and mi¬ crobiology staff was significantly higher than that in the pathology staff, which suggests a greater risk for hepatitis B among the former staff than among the latter. Other staff from smaller specialized laboratories who handle few or no clinical specimens showed a significantly lower pre¬ valence of anti-HBs compared with chemistry and hema¬ tology staff but not with microbiology staff; this indicates that microbiology staff may handle clinical specimens more carefully. This prevalence of anti-HBs among staff of several diag¬ nostic laboratories at The Wellesley Hospital is comparable with figures from another Canadian study,3 in which the incidence of clinical viral hepatitis in laboratory staff in a hospital between 1964 and 1973 was studied: probable viral hepatitis occurred in 22 laboratory staff 17 in bio¬ chemistry, 4 in hematology and 1 in microbiology; anti-HBs
the
history of
0.05.
hepatitis
had anti-HBs, but of the 383 staff without a history of hepatitis only 46 (12.0%)= had anti-HBs (Table VI) a significant difference (P 0.05). There was no significant difference in prevalence of anti-HBs between those with and those without previous blood transfusions.
history of
found in 26% of "bench workers" but in no students administrative staff. Among nurses in high-risk groups, three of the nine on the intravenous team had anti-HBs; one of the three had a history of hepatitis, as did one without anti-HBs. This in¬ dicates that these nurses are at a high risk for hepatitis B. Nurses working on high-risk wards also had a significantly higher prevalence of anti-HBs compared with administrative personnel. There was no difference in prevalence of antiHBs between nurses working in the high-risk wards and those working in intermediate-risk areas. This may be because nurses are rotated to different areas or because of previous exposure in high-risk areas. Therefore, regard¬ less of their location in the hospital, nurses are at a signi¬ ficantly higher risk for hepatitis B than administrative staff. An unexpected finding was the absence of anti-HB. in the staff of the renal dialysis unit, none of whom had a history of hepatitis. The prevalence of anti-HBs in 15 hemodialysis centres in the United States was found to vary widely, from 7.7 to 55.5% (mean, 34%) among patients, and from 0 to 61.5% (mean, 31.3%) among attending medical staff.11 This variation may be due to differences in hygienic measures and in the quality of the blood used for transfusion. We found previously that 1.3% of blood units that had been routinely screened by the Red Cross
was or
?Difference significant at P 0.05. fTwo of the nine also had a history of transfusion. also had a history of transfusion. jThe one staff member not given because numbers are so small. Percentages § Difference significant at P 0.05. =
=
*=
Table VI.Prevalence of anti-HB, in staff (n = 426) with without history of hepatitis or blood transfusions
?Difference significant at P 0.05. 846 CMA JOURNAL/NOVEMBER 8, 1975/VOL. 113 =
or
by counterimmunoelectrophoresis still contained HB5Ag when tested with the current, generally accepted RIA test.1' Administrative staff had the lowest prevalence of antiHB8 (6.1 %). Ward secretaries, who perform only clerical tasks at the nursing stations, had a similar prevalence (7.7%). However, the clerical staff of the laboratories had a higher prevalence (14.3%) of anti-HB, than the administrative staff and ward secretaries, and this prevalence was slightly higher than that of the general-duty nurses. This may indicate that the contact of the ward secretaries with patients on the ward may not provide an important means of transfer of hepatitis B agents compared with the exposure of the clerical staff to blood, blood products and patients' specimens in the laboratories. Significantly more staff with anti-HB, had a history of hepatitis (19.3%) compared with staff without anti-HB. (7.9%), and significantly more staff with a history of hepatitis had anti-HB, (25.6%) compared, with staff without such a history (12.0%). This confirms the previous finding of a positive relation between the presence of anti-HB5 and a history of hepatitis. A significantly larger percentage of the laboratory staff with anti-HB8 gave a history of hepatitis, compared with laboratory staff without anti-HB,. A similar high frequency of a history of hepatitis was found in another study3 of laboratory workers with anti-HB,: 14 of 33 gave such a history. A history of blood transfusion was found not to be a significant factor in the prevalence of anti-HB.. Anti-HB, is more prevalent in individuals who have had hepatitis. Its production is probably controlled by a humoral immune mechanism, although there is evidence that a cellular immune mechanism is also involved: Ibrahim, Girish and Perkins13 have postulated that the absence of anti-HB5 from the serum for several months after the disappearance of HB.Ag reflects cell-mediated immunity alone, and that the late appearance of anti-HB. indicates a secondary response to additional exposure to HB.Ag. This theory is supported by our finding that laboratory workers, predominantly from clinical chemistry and hematology laboratories, have the highest prevalence of anti-HB5. These technologists are continuously exposed to blood and clinical specimens from infected patients, which provides a continuous stimulus
to the production and possibly the maintenance of anti-HB. Our study, therefore, shows conclusively that health personnel who are in contact with patients or handle blood and other specimens from patients, or blood products, are at an increased risk for hepatitis B. Contact with patients seems to be less important than contact with patients' blood or other specimens. We are indebted to the nurses of the intravenous team at The Wellesley and The Princess Margaret hospitals and Mrs. Karen Hume, PHN, for their help in obtaining the blood samples. We thank Mr. Victor Ammah for statistical analysis of the results, the technical staff of the virus unit of the department of microbiology, and Miss Elizabeth Nimmo for preparation of the manuscript. We also sincerely thank all staff volunteers of The Wellesley and The Princess Margaret hospitals, without whose cooperation the study would not have been possible. References 1. CHERUBIN C, PURCELL RH, LANDER ii, et al: Acquisition of antibody to hepatitis B antigen in three socioeconomically different medical populations. Lancet 2: 149, 1972 2. COWAN DH, KOuROur'Is GM, LEERS W-D: Occurrence of hepatitis and hepatitis B surface antigen in adult patients with acute leukemia. Can Med Assoc J 112: 693, 1975 3. BisH.i FR, LARZOFFSKY NA, RHODES AJ, et al: Hepatitis type B: studies on antigens and antibodies in laboratory staff. Epidemiol Bull 18: 137, 1974 4. LANDER ii, ALTER HJ, PURCELL RH: Frequency of antibody to hepatitis-associated antigen as measured by a new radioimmunoassay technique. J Immunol 106: 1166, 1971 5. Lawns TL, ALTER HJ, CHALMERS TC, et al: A comparison of the frequency of hepatitis-B antigen and antibody in hospital and nonhospital personnel. N Engi J Med 289: 647, 1973 6. BISHAI FR, SPENCE L, BAILEY TJ, et al: Frequency of hepatitis B antigen and antibody in pregnant women and .alth-care personnel. Hepatitis Scientific Memoranda Memo H-843, Mar 1975, p 7 7. ASHCAVAI M, PETERS RL: Manual for Hepatitis B Antigen Testing, Toronto, Saunders, 1973 8. VYAS GN, SHULMAN NR: Haemagglutination assay for antigen and antibody associated with viral hepatitis. Science 170: 332, 1970 9. HOLLINGER FB, VORNDAM V. DREESMAN GR: Assay of Australia antigen and antibody employing double-antibody and solid-phase radioimmunoassay techniques and comparison with the passive hemaggiutination methods. J Immunol 107: 1099, 1971 10. WALSH JH, YALOW R, BERSON SA: Detection of Australia antigen and antibody by means of radioimmunoassay techniques. I Infect Dis 121: 550, 1970 11. SZMUNESS W, PRINCE AM, GRADY GF, et al: Hepatitis B infection: a point-prevalence study in 15 US hemodialysis centers. JAMA 227: 901, 1974 12, LEERS W-D, KouRouPis GM: Hepatitis B antigen in screened blood units for transfusion in renal dialysis patients. Can Med Assoc / 110: 308, 1972 13. IBRAHIM AB, GIRIsH GN, PERKINS HA: Immune response to hepatitis B surface antigen. Infect Immunol 11: 137, 1975
CMA JOURNAL/ NOVEMBER 8, 1975/VOL. 113 847
PH
D,
FRCP[c],
DIP
BACT, CPH; G.M.
KoUROUPIS,J
D SC, M
SC, FRSH, CPH, FRMS
Summary: Of 426 hospital staff tested for hepatitis B surface antibody (anti-HBs) by the radioimmunoassay method 57 (13.4%) had positive results. Laboratory staff had the highest prevalence, followed by nurses, and both values were significantly higher than that of administrative staff. Clerical staff working in laboratories were at the same risk for hepatitis B as general-duty
avec la presence d'anti-HBs. Le risque d'hepatite B est plus eleve chez les membres du personnel hospitalier qui sont en contact direct avec ces malades. II faut cependant noter que le contact avec les malades est moins important que le contact avec le sang ou avec d'autres echantillons de ces malades.
nurses.
The prevalence of hepatitis B surface antibody (anti-HBs) varies widely in different population groups, apparently being about 40% in lower socioeconomic groups and about 50% among drug addicts.1 The prevalence of anti-HBs also varies among patients and hospital personnel. It is well known that the incidence of hepatitis B is higher in patients who have received multiple blood trans¬ fusions,2 and that hepatitis B is a hazard for laboratory personnel handling blood or blood products.3 One study* showed the prevalence of anti-HBs to be 14.4% in volun¬ teer blood donors, 22.6% in commercial blood donors, 14.8% in blood bank personnel, 11.4% in laboratory per¬ sonnel and 82.6% in persons who had received multiple transfusions. A recent study in a hospital population revealed that anti-HBs was twice as frequent among health personnel compared with controls not exposed to blood products.5 A more recent study in Ontario6 determined the following prevalence figures for anti-HBs: staff of renal dialysis unit, 16.0%; staff of institutions for the mentally retarded, 12.5%; and patients of these institutions, 44.3%. We determined the prevalence of anti-HBs in hospital staff by comparing groups at high risk for hepatitis B with those at low risk.
Significantly more staff with anti-HBs had a history of hepatitis (19.3%) compared with staff without anti-HBs (7.9%), and significantly more staff with a history of hepatitis had anti-HBs (25.6%) compared with staff without such a history (12.0%). History of blood transfusions was not related to prevalence of anti-HBg. The risk for hepatitis B is greater in hospital staff who are in direct contact with patients or handle patients' blood and other specimens. However, contact with patients is less important than contact with patients' blood and other specimens. Resume: Sur 426 membres du personnel hospitalier chez lesquels nous avons recherche I'anticorps de surface de I'hepatite B (anti-HBJ par la technique radioimmunologique, 57 (13.4%) donnaient des resultats positifs. Les techniciens de laboratoire etaient les plus touches, suivis des infirmieres, et ces deux valeurs etaient significativement plus elevees que celles trouvees parmi le personnel administratif. Toutefois, les employes administratifs travaillant dans les laboratoires etaient sujets au meme risque d'hepatite B que les infirmieres generales. Un nombre significativement plus eleve de personnes porteurs de l'anti-HBs avaient des antecedents d'hepatite (19.3%) par comparaison avec des personnes sans anti-HBs (7.9%), et un nombre significativement plus eleve de personnes ayant des antecedents d'hepatite avaient des anti-HBs (25.6%) par comparaison avec ies sujets n'ayant pas
ces
antecedents (12.0%). Des transfusions anterieures
Presented at the conjoint annual meeting of the Canadian Association of Medical Microbiologists, Calgary, June 25 to 29, 1975 From the department of medical microbiology, faculty of medicine, University of Toronto, and the department of microbiology, The Wellesley Hospital, Toronto tChief, department of microbiology, The Wellesley Hospital; assistant department of medical microbiology, University of Toronto Virologist, department of microbiology, The Wellesley Hospital Reprint requests to: Dr. W-D. Leers, The Wellesley Hospital, 160 Wellesley St. E, Toronto, ON M4Y 1J3
?rofessor,
844 CMA JOURNAL/NOVEMBER 8, 1975/VOL. 113
n'avaient pas de rapport
Materials and methods
Subjects and blood samples Three risk groups of hospital personnel were defined: the high-risk group consisted of staff having routine direct contact with patients, their blood or secretions, or blood products; the low-risk group consisted of staff having no such direct contact; and the intermediate-risk group con¬ sisted of staff who could not be placed in either the highor the low-risk group. The infection control nurse gave an explanatory letter to each department head and explained the study to the
participants (61 men and 365 women), all of whom volunteers. Every participant completed a question¬ naire about history of hepatitis, blood transfusions and other relevant information. Blood samples were collected by nurses of the intra¬ venous team and sent to our virus laboratory, where the serum was separated and stored at 4°C. Assay for anti-HBs was begun after all 426 samples had arrived.
although the difference was not significant. However, the clerical staff and general-duty nurses had a significantly higher (P = 0.10) prevalence of anti-HBs compared with the administrative personnel. The low-risk group consisted of 23 senior administrators and supervisory personnel and 59 clerical staff. There was no significant difference in the prevalence of anti-HBs between the two groups.
Radioimmunoassay for anti-HBs
Laboratory personnel at high risk The prevalence of anti-HBs among the various types of laboratory personnel is given in Table II. Professional and technical staff are included but clerical staff are omitted because they are considered an intermediate-risk group. There was no significant difference in the prevalence of anti-HBs between clinical chemistry, hematology and micro¬ biology staff, but the prevalence of anti-HBs in the clinical pathology staff was significantly lower (P 0.05) than that in the former three groups. The prevalence in the "other laboratory staff was also significantly lower compared with that of the clinical chemistry and hematology (P 0.05) and microbiology (P 0.10) staff.
426
were
Anti-HBs in serum was detected by the direct solid-phase radioimmunoassay (RIA) technique, which has proven prac¬ tical for assay of anti-HBs.710 We used the Ausab* kit, which contains plastic beads coated with anti-HBs. To a tube containing a coated glass bead was added 0.2 ml of serum; the tube was incubated for 16 to 20 hours at room temperature. If antibody was present it attached to the solid-phase antigen. Then 0.2 ml of hepatitis B surface antigen (HBsAg) tagged with iodine-125 was added. During 4 hours' incubation at room temperature the antigen at¬ tached to the antibody, creating a tagged antigen-antibodyantigen "sandwich". Statistical analysis The chi-square (x2) test was applied for a sample size less than 30 if the smallest expected value was greater than five; if this value was smaller than five the Fisher exact probability test was applied. The test for normal distribu¬ tion was used for a sample size greater than 30. Results There was no significant difference in prevalence of antiHBs between the male and female staff. The prevalence of anti-HBs in the three risk groups is given in Table I. The overall prevalence in the high-risk group differed significantly (P = 0.05) from that in the low-risk group, but the overall prevalence in the intermediate-risk group did not differ significantly from that in either the high- or low-risk group. In the high-risk group the laboratory staff had a signifi¬ cantly higher (P = 0.05) prevalence of anti-HBs compared with the nurses. In the intermediate-risk group the clerical staff of the laboratories and the general-duty nurses had a similar and higher prevalence of anti-HBs than the ward secretaries, *Abbott Laboratories, North Chicago. all technical details.
Accompanying pamphlet provides
=
=
=
Nurses at high risk The prevalence of anti-HBs in nurses in the high-risk group is given in Table III. There was a significant differ¬ ence (P = 0.10) in prevalence between nurses on the intra¬ venous team and nurses in the renal dialysis unit.
Hepatitis and blood transfusions The relation of a history of hepatitis or blood transfu¬ or both, with the presence of anti-HBs is presented in Table IV. Two laboratory technicians and one ward
sions,
Table II.Prevalence of anti-HBs in
laboratory personnel*
?Including physicians, scientists, technologists and laboratory assistants in high-risk groups. disease, medicine, biophysics, respiratory technology. jResearch, rheumatic between this group and first three groups significant at P 0.05. JDifference § Difference between this group and first two groups significant at P 0.05, and between this group and microbiology group, at P 0.10. =
=
Table I.Prevalence of hepatitis B surface in risk groups of hospital staff Total
Group
no.
§ Difference significant at P 0.10. =
antibody (anti-HBJ Anti-HB8-positive no. (and %)
=
Table lll.Prevalence of anti-HBs in
Total
Area or service
?Difference significant at P
nurses no.
=
in
high-risk
areas
Anti-HB8-positive no. (and %)
0.10.
CMA JOURNAL/NOVEMBER 8, 1975/VOL. 113 845
secretary gave a history of both hepatitis and blood trans¬ fusions. A significantly larger (P = 0.05) number of staff with anti-HBs than without had a history of hepatitis, and a significantly larger (P = 0.05) number of staff with antiHBs had a history of hepatitis than of transfusions. There was no significant difference with respect to the history of blood transfusions between staff with and without anti-HBs. A more detailed analysis is presented in Table V. A his¬ tory of hepatitis was given by 24% of the laboratory staff with anti-HBs but by only 9.2% of the laboratory staff without anti-HBs; the difference is significant (P = 0.05). For each of the other groups there was no significant dif¬ ference in the percentage with a history of hepatitis between those with and those without anti-HBs. However, the per¬ centage of all staff with a history of hepatitis and anti-HBs, 19.3, was significantly higher (P = 0.05) than that of all staff with a history of hepatitis but without anti-HBs, 8.7. Also, the percentage of anti-HBs-positive laboratory staff with a history of hepatitis was significantly higher (P = 0.05) than the percentage for the other anti-HBs-positive groups. Of the 43 staff with a history of hepatitis 11 (25.6%) Table IV.Prevalence of anti-HBg in staff with hepatitis or blood transfusion or both
History Hepatitis Transfusions Hepatitis and
Anti-HB8-positive (n 57) no. (and %) no. (and %) 11 (19.3)*t 40(9.4) 31 (7.3) 3(5.3)f 0(0) 3(0.7) 14 (24.6) 74(17.4) Total
transfusions Total ?Difference significant at P fDifference significant at P
= =
=
Anti-HBs-negative (n 369) no. (and %) 29 ( 7.9)* 28 ( 7.6) 3 ( 0.8) 60 (16.3) =
0.05.
Table V.Prevalence of anti-HBs in staff with
.
Discussion Our results confirm that hospital laboratory personnel are at an increased risk for hepatitis B and have a high prevalence of anti-HBs.5 We found no significant difference in prevalence between the sexes. However, the prevalence of anti-HBs in the hospital staff we surveyed (13.4%) was not significantly different from that (14.8%) in 1004 unselected patients whose sera we tested previously (unpublished data). The high-risk group, laboratory staff and nurses having routine direct contact with patients, their blood or secretions, or blood products, had a significantly higher prevalence of anti-HBs (16.5%) than the low-risk group (6.1%), administrative staff having no such direct contact.
Among laboratory staff, the clinical chemistry staff had highest prevalence of HBsAg (40.0%), followed by hematology (32.0%) and microbiology (20.8%) staff. None of the pathology staff, including pathologists, had anti-HBs; pathology technologists usually handle noninfectious, formolized specimens, but the pathologist who performs autop¬ sies is at an increased risk for hepatitis B. The prevalence of anti-HBs in the clinical chemistry, hematology and mi¬ crobiology staff was significantly higher than that in the pathology staff, which suggests a greater risk for hepatitis B among the former staff than among the latter. Other staff from smaller specialized laboratories who handle few or no clinical specimens showed a significantly lower pre¬ valence of anti-HBs compared with chemistry and hema¬ tology staff but not with microbiology staff; this indicates that microbiology staff may handle clinical specimens more carefully. This prevalence of anti-HBs among staff of several diag¬ nostic laboratories at The Wellesley Hospital is comparable with figures from another Canadian study,3 in which the incidence of clinical viral hepatitis in laboratory staff in a hospital between 1964 and 1973 was studied: probable viral hepatitis occurred in 22 laboratory staff 17 in bio¬ chemistry, 4 in hematology and 1 in microbiology; anti-HBs
the
history of
0.05.
hepatitis
had anti-HBs, but of the 383 staff without a history of hepatitis only 46 (12.0%)= had anti-HBs (Table VI) a significant difference (P 0.05). There was no significant difference in prevalence of anti-HBs between those with and those without previous blood transfusions.
history of
found in 26% of "bench workers" but in no students administrative staff. Among nurses in high-risk groups, three of the nine on the intravenous team had anti-HBs; one of the three had a history of hepatitis, as did one without anti-HBs. This in¬ dicates that these nurses are at a high risk for hepatitis B. Nurses working on high-risk wards also had a significantly higher prevalence of anti-HBs compared with administrative personnel. There was no difference in prevalence of antiHBs between nurses working in the high-risk wards and those working in intermediate-risk areas. This may be because nurses are rotated to different areas or because of previous exposure in high-risk areas. Therefore, regard¬ less of their location in the hospital, nurses are at a signi¬ ficantly higher risk for hepatitis B than administrative staff. An unexpected finding was the absence of anti-HB. in the staff of the renal dialysis unit, none of whom had a history of hepatitis. The prevalence of anti-HBs in 15 hemodialysis centres in the United States was found to vary widely, from 7.7 to 55.5% (mean, 34%) among patients, and from 0 to 61.5% (mean, 31.3%) among attending medical staff.11 This variation may be due to differences in hygienic measures and in the quality of the blood used for transfusion. We found previously that 1.3% of blood units that had been routinely screened by the Red Cross
was or
?Difference significant at P 0.05. fTwo of the nine also had a history of transfusion. also had a history of transfusion. jThe one staff member not given because numbers are so small. Percentages § Difference significant at P 0.05. =
=
*=
Table VI.Prevalence of anti-HB, in staff (n = 426) with without history of hepatitis or blood transfusions
?Difference significant at P 0.05. 846 CMA JOURNAL/NOVEMBER 8, 1975/VOL. 113 =
or
by counterimmunoelectrophoresis still contained HB5Ag when tested with the current, generally accepted RIA test.1' Administrative staff had the lowest prevalence of antiHB8 (6.1 %). Ward secretaries, who perform only clerical tasks at the nursing stations, had a similar prevalence (7.7%). However, the clerical staff of the laboratories had a higher prevalence (14.3%) of anti-HB, than the administrative staff and ward secretaries, and this prevalence was slightly higher than that of the general-duty nurses. This may indicate that the contact of the ward secretaries with patients on the ward may not provide an important means of transfer of hepatitis B agents compared with the exposure of the clerical staff to blood, blood products and patients' specimens in the laboratories. Significantly more staff with anti-HB, had a history of hepatitis (19.3%) compared with staff without anti-HB. (7.9%), and significantly more staff with a history of hepatitis had anti-HB, (25.6%) compared, with staff without such a history (12.0%). This confirms the previous finding of a positive relation between the presence of anti-HB5 and a history of hepatitis. A significantly larger percentage of the laboratory staff with anti-HB8 gave a history of hepatitis, compared with laboratory staff without anti-HB,. A similar high frequency of a history of hepatitis was found in another study3 of laboratory workers with anti-HB,: 14 of 33 gave such a history. A history of blood transfusion was found not to be a significant factor in the prevalence of anti-HB.. Anti-HB, is more prevalent in individuals who have had hepatitis. Its production is probably controlled by a humoral immune mechanism, although there is evidence that a cellular immune mechanism is also involved: Ibrahim, Girish and Perkins13 have postulated that the absence of anti-HB5 from the serum for several months after the disappearance of HB.Ag reflects cell-mediated immunity alone, and that the late appearance of anti-HB. indicates a secondary response to additional exposure to HB.Ag. This theory is supported by our finding that laboratory workers, predominantly from clinical chemistry and hematology laboratories, have the highest prevalence of anti-HB5. These technologists are continuously exposed to blood and clinical specimens from infected patients, which provides a continuous stimulus
to the production and possibly the maintenance of anti-HB. Our study, therefore, shows conclusively that health personnel who are in contact with patients or handle blood and other specimens from patients, or blood products, are at an increased risk for hepatitis B. Contact with patients seems to be less important than contact with patients' blood or other specimens. We are indebted to the nurses of the intravenous team at The Wellesley and The Princess Margaret hospitals and Mrs. Karen Hume, PHN, for their help in obtaining the blood samples. We thank Mr. Victor Ammah for statistical analysis of the results, the technical staff of the virus unit of the department of microbiology, and Miss Elizabeth Nimmo for preparation of the manuscript. We also sincerely thank all staff volunteers of The Wellesley and The Princess Margaret hospitals, without whose cooperation the study would not have been possible. References 1. CHERUBIN C, PURCELL RH, LANDER ii, et al: Acquisition of antibody to hepatitis B antigen in three socioeconomically different medical populations. Lancet 2: 149, 1972 2. COWAN DH, KOuROur'Is GM, LEERS W-D: Occurrence of hepatitis and hepatitis B surface antigen in adult patients with acute leukemia. Can Med Assoc J 112: 693, 1975 3. BisH.i FR, LARZOFFSKY NA, RHODES AJ, et al: Hepatitis type B: studies on antigens and antibodies in laboratory staff. Epidemiol Bull 18: 137, 1974 4. LANDER ii, ALTER HJ, PURCELL RH: Frequency of antibody to hepatitis-associated antigen as measured by a new radioimmunoassay technique. J Immunol 106: 1166, 1971 5. Lawns TL, ALTER HJ, CHALMERS TC, et al: A comparison of the frequency of hepatitis-B antigen and antibody in hospital and nonhospital personnel. N Engi J Med 289: 647, 1973 6. BISHAI FR, SPENCE L, BAILEY TJ, et al: Frequency of hepatitis B antigen and antibody in pregnant women and .alth-care personnel. Hepatitis Scientific Memoranda Memo H-843, Mar 1975, p 7 7. ASHCAVAI M, PETERS RL: Manual for Hepatitis B Antigen Testing, Toronto, Saunders, 1973 8. VYAS GN, SHULMAN NR: Haemagglutination assay for antigen and antibody associated with viral hepatitis. Science 170: 332, 1970 9. HOLLINGER FB, VORNDAM V. DREESMAN GR: Assay of Australia antigen and antibody employing double-antibody and solid-phase radioimmunoassay techniques and comparison with the passive hemaggiutination methods. J Immunol 107: 1099, 1971 10. WALSH JH, YALOW R, BERSON SA: Detection of Australia antigen and antibody by means of radioimmunoassay techniques. I Infect Dis 121: 550, 1970 11. SZMUNESS W, PRINCE AM, GRADY GF, et al: Hepatitis B infection: a point-prevalence study in 15 US hemodialysis centers. JAMA 227: 901, 1974 12, LEERS W-D, KouRouPis GM: Hepatitis B antigen in screened blood units for transfusion in renal dialysis patients. Can Med Assoc / 110: 308, 1972 13. IBRAHIM AB, GIRIsH GN, PERKINS HA: Immune response to hepatitis B surface antigen. Infect Immunol 11: 137, 1975
CMA JOURNAL/ NOVEMBER 8, 1975/VOL. 113 847
