ORIGINAL RESEARCH * NOUVEAUTES EN RECHERCHE
Prevalence of bloodborne infective agents among people admitted to a Canadian hospital Marie Louie,*t MD; Donald E. Low,*t MD; S. Victor Feinman,*t MD; Bernadette McLaughlin,tt MD; Andrew E. Simor,*t MD Objective: To determine the prevalence rates of hepatitis B surface antigen (HBsAg) and antibodies to the human immunodeficiency virus (anti-HIV) and the hepatitis C virus (anti-HCV) among people admitted to an urban Canadian hospital. Design: Anonymous unlinked serosurvey. Setting: A 420-bed teaching hospital in Toronto. Participants: All 3000 patients admitted to the hospital on weekdays from January to June 1990. An attempt was made to exclude those who were readmitted during the study period. Interventions: Serum samples from all the patients were tested for HBsAg and anti-HIV, and 1306 samples were also tested for anti-HCV by means of enzyme immunosorbent assays; reactions were confirmed by means of specific antibody neutralization or immunoblot assay. Main results: The prevalence rates of HBsAg, anti-HIV and anti-HCV were 2.1% (95% confidence interval [CI] 1.6% to 2.6%), 0.6% (95% CI 0.3% to 0.9%) and 0.5% (95% CI 0.1% to 0.9%) respectively. Conclusions: This is the first report defining rates of infection with these bloodborne agents among patients admitted to a Canadian hospital. The observed rates likely reflect the patient population served by our hospital and do not necessarily apply to other Canadian centres. The results support the use of universal precautions in health care settings. Objectif: Preciser les taux de prevalence de l'antigene de surface de l'hepatite B (AgHBs) et des anticorps au virus de l'immunodeficience humaine (anti-VIH) et au virus de l'hepatite C (anti-VHC) chez les personnes admises dans un h6pital urbain canadien. Conception: Enquete serologique anonyme non reliee. Contexte: H6pital d'enseignement de 420 lits a Toronto. Participants: La totalite des 3 000 patients admis a l'h6pital en semaine de janvier a juin 1990. Nous avons essaye d'exclure ceux qui ont ete readmis pendant la periode de l'etude. Interventions: Nous avons analyse les echantillons seriques de tous les patients pour depister les AgHBs et anti-VIH et analyse en outre 1 306 prelevements pour depister les anti-VHC par dosage enzymatique immunosorbant; les reactions ont ete confirmees par neutralisation specifique des anticorps ou dosage d'immunotransfert. Resultats principaux: Les taux de prevalence des AgHBs, anti-VIH et anti-VHC etaient respectivement de 2,1 % (intervalle de confiance [IC] de 95 %, 1,6 % a 2,6 %), 0,6 % (IC de95%,0,3%aO,9%)etO,5%(ICde95%,0,1 %aO,9%). Conclusions: C'est le premier rapport precisant les taux d'infection a ces agents a From the departments of Microbiology and Medicine, *Mount Sinai Hospital and tUniversity of Toronto, Toronto, Ont., and $the Public Health Laboratory of Ontario, Toronto, Ont.
Reprint requests to: Dr. Andrew E. Simor, Department ofMicrobiology, Rm. 602, Mount Sinai Hospital, 600 University Ave., Toronto, ON M5G IX5 APRIL 15, 1992
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diffusion hematogene chez les patients admis dans un hopital canadien. Les taux constates rendent probablement compte de la population de patients desservis par notre hopital et ne s'appliquent pas necessairement aux autres centres canadiens. Les resultats prechent en faveur du recours a des precautions universelles dans les milieux de soins de sante.
T ransmission of bloodborne viral pathogens, such as hepatitis B virus, hepatitis C virus (HCV) and human immunodeficiency virus (HIV), from infected patients through accidental percutaneous inoculation poses a significant risk to health care workers. Efforts to reduce this risk include adoption of universal precautions, as recommended by the US Centers for Disease Control, Atlanta,' and the Laboratory Centre for Disease Control, Ottawa.2 These guidelines recommend that blood and other body fluids from all patients be considered potentially infectious. In contrast, some have suggested that health care workers have a right, if not a need, to know whether their patients are infected with a bloodborne pathogen and that laboratory specimens from infected patients be identified with a "biohazard" label.3'4 Others have proposed that routine testing of all patients in hospital be done to identify those infected with HIV.5 6 Decisions regarding the appropriateness of these policies depend, in part, on knowledge of the prevalence of hepatitis B, hepatitis C and HIV infection in patients in hospital. This information is also useful for describing the epidemiologic features of infection due to these pathogens in patients admitted to hospital and for estimating the effect of these infections on hospital admission rates. Although a few studies have reported the prevalence of hepatitis B and HIV infection in US hospitals7'8 similar Canadian data do not exist, and there are no such data regarding hepatitis C. We therefore determined the prevalence of hepatitis B surface antigen (HBsAg), HIV antibody (anti-HIV) and HCV antibody (antiHCV) among patients admitted to our hospital using an anonymous unlinked serosurvey.
Methods Mount Sinai Hospital is a 420-bed teaching hospital in Toronto, with approximately 18 500 discharges annually. About 40% of the inpatients are Jewish, originally coming to Canada from eastern and central Europe. As well, the hospital has a strong outreach program with Toronto's large Chinese community. The hospital has busy medical, surgical and obstetrics services and a 15-bed medical-surgical intensive care unit. There is a high-risk pregnancy program and a large neonatal intensive care unit but no pediatrics department. There is a liver investigation unit and an oncology program. No cardiovascular surgery, organ transplantation or hemodialysis is 1332
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done at the hospital. Although the hospital has no sexually transmitted diseases clinic there is an outpatient neuropsychiatric clinic for people with HIVrelated concerns that sees 250 to 300 new referrals per year (3400 visits annually). Over the past 5 years the hospital provided inpatient care for 3 to 5 patients with known HIV-related illnesses per 1000 discharged patients each year. Between January and June 1990 leftover blood from samples obtained from newly admitted patients for determination of the complete blood count was collected from Monday to Friday each week. We attempted to exclude specimens if another sample from the same patient had already been obtained. However, some specimens from patients who were readmitted were probably included. The patient's age and sex were noted; all other identifying information was removed. Subsequent handling and testing were done by personnel who had not seen the specimens before removal of identifying information. Samples were centrifuged at 1600 x g for 10 minutes and then transferred to tubes, assigned a consecutive numeric code and stored at - 70°C until serologic testing was performed. Enzyme immunosorbent assays were used to detect HBsAg (Auszyme Monoclonal, Abbott Laboratories, Chicago), anti-HIV (HIVAB, Abbott Laboratories) and anti-HCV (Ortho HCV Antibody, Ortho Diagnostics Systems, Markham, Ont.). Testing was performed according to the manufacturers' instructions. It was determined that the use of blood treated with ethylenediamine tetra-acetate would not interfere with the serologic assays. Samples found to be repeatedly reactive were subjected to specific antibody neutralization (HBsAg Confirmatory, Abbott Laboratories), a previously described in-house immunoblot assay for anti-HIV9 or recombinant immunoblot assay (HCV RIBA-I, Ortho Diagnostics Systems), as appropriate. The study received ethical approval from the University of Toronto Review Committee on the Use of Human Subjects and was conducted in accordance with published guidelines on ethical considerations regarding anonymous unlinked seroprevalence research.'0
Results During the 6 months of the study 9305 people were admitted to the hospital; 4192 were excluded because they were readmitted during the study LE 1 5 AVRIL 1992
infection had not been previously detected. Clinical markers and determinants of risk factors were not found to be reliable predictors of infection; this lends support to the role of universal precautions. During our study 43 patients identified as having HIV infection were discharged from hospital (4.6 per 1000 discharges), and anti-HIV was detected in 6.3 per 1000 samples; this suggests that in few of the cases was the HIV infection undetected during the patient's hospital stay. The extent of variation in HIV infection rates also reinforces the need for caution in the interpretation of HIV seroprevalence data from any one centre or geographic area. Although the HIV infection rate was relatively low in our study the HBsAg carrier rate (2.1%) was 2.6 times higher than the rate of 0.8% found by Feinman and colleagues'4 among patients admitted to the same hospital 16 years earlier. This is an unexpectedly high prevalence rate for HBsAg, given that the US national rate is estimated to be only 0.2%,1' and the rate among Canadian blood donors is 0.06% (Barbara Buchner, head, Virology Section, National Reference Laboratory, Canadian Red Discussion Cross: personal communication, 1991). Our results Occupational exposure to bloodborne infective are, however, similar to the rate of 2.0% reported by agents remains a significant risk to health care Gordin and associates.8 The greater number of workers in hospitals despite recommendations for HBsAg carriers admitted to our hospital may be implementation of universal precautions. The risk of related to the activities of the liver study unit but HIV infection from a single needle-stick injury probably also reflects the increased population of involving blood known to be infected with HIV is immigrants from endemic areas attending the hospiestimated to be about 0.3% to 0.4%.11,12 The risk of tal in the past decade. This is the first report of the prevalence of hepatitis B after exposure to infected blood is much higher, 10% to 35%.12 However, the cumulative risk anti-HCV among inpatients in North America and of a bloodborne infection depends in part on the demonstrates a low rate of infection (0.5%) in our prevalence of these infections among patients in patient population. A recent Canadian survey found an anti-HCV seroprevalence rate of 2.0% in an hospital. Seroprevalence surveys for HIV infection at undefined population of 256 "normal individuals" selected sentinel hospitals in the United States re- and only 0.4% among blood donors,'6 which is vealed that 1.3% of 89 547 specimens were HIV similar to our rate. The low prevalence rate may be positive.7 However, infection rates varied more than attributable, in part, to limitations of the currently 70-fold among the hospitals, from as low as 0.1% to available serologic tests for hepatitis C antibody. as high as 7.8%. Specimens from patients known to Enzyme immunoassays and supplementary tests, have HIV infection were excluded; therefore, the such as the recombinant immunoblot assay, lack seroprevalence estimates represent minimal rates of adequate sensitivity and specificity.'7 In our study infection. the first-generation recombinant immunoblot assay The seroprevalence rate of 0.6% for HIV infec- confirmed the HCV seropositivity of only 7 of the 22 tion among our patients is much lower than the 3.7% samples repeatedly reactive in the enzyme imfound by Gordin and associates8 among 616 patients munoassay. At least some of the other 15 samples admitted to a Veterans Administration hospital in may also have been seropositive, and newer, secondWashington in 1987. Almost all of the patients in generation test kits may give more accurate results. that study were men, and nearly 40% had used Although the role of HCV in transfusionintravenous drugs, had engaged in high-risk sexual associated non-A, non-B hepatitis is now well estabactivities or had previously received a blood transfu- lished, its implications for the health care worker sion. Our rate is also lower than the 5.2% observed with percutaneous exposure are less certain. Neverby Kelen and collaborators'3 among patients present- theless, health care workers who have frequent ing to the emergency department of an inner-city contact with blood have been found to be at inhospital in Baltimore. In most of the cases the creased risk of non-A, non-B hepatitis,'8 and acute
period. Of the remaining 5113 patients serum samples were obtained from the 3000 admitted on weekdays. People admitted through the Emergency Department accounted for 19.3% of all admissions; the remaining 80.7% were admitted directly to the wards (33.4% to the surgical wards, 30.3% to the obstetrics or gynecology services, 14.4% to the medical wards and 21.9% to other services). The mean age of the 3000 patients was 49 years (extremes 14 and 99 years); 66.0% were female. During the study period 43 patients known to have HIV-related medical problems were discharged from the hospital (4.6 per 1000 discharges). All of the 3000 serum samples were tested for HBsAg and anti-HIV; HBsAg was detected in 2.1% (95% confidence interval [CI] 1.6% to 2.6%) and anti-HIV in 0.6% (95% CI 0.3% to 0.9%). Twentytwo (1.7%) of the 1306 samples tested for anti-HCV were repeatedly reactive; however, only 7 (0.5%) were also positive in the recombinant immunoblot assay (95% CI 0.1% to 0.9%).
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hepatitis C was documented in 3 (2.7%) of 110 workers exposed to HCV through a needle-stick injury.19 Although HCV transmission through such a route may be infrequent it clearly does occur and places the health care worker at risk. Anonymous seroprevalence surveys may provide the most accurate and comprehensive means of determining HIV infection rates, provided certain ethical standards and guidelines are met,'0 but potential biases did exist in our study. Samples were not tested from all people admitted to the hospital during the study period, and it could be argued that those tested were not representative of the hospital's patient population. For example, the large number of patients admitted on Sundays for elective surgery were excluded. It is also possible that the proportions of patients in the study admitted to the hospital services were different from the proportions of all patients admitted to those services during the same period. However, the age and sex distribution of those tested was similar to that of all people admitted during the study period. Unfortunately, no other clinical or demographic information was available. Because the survey was blind and unlinked, self-selection by patients should not have biased the sample. We attempted to exclude samples from people readmitted during the study period but may not always have been successful. Repeat testing of people readmitted with HIV infection or chronic hepatitis may have increased the observed infection rates but would nevertheless be indicative of the number of infected inpatients at any one time. Are our results generalizable to other hospital settings? Our hospital is a teaching hospital in an urban centre, with a large referral base. Nearly two-thirds of the admissions are of women, in part probably because of a busy obstetrics service. The hospital is not a major referral centre for patients with HIV infection but does serve patients with diverse ethnic origins, including many from areas highly endemic for chronic hepatitis B. Thus, although our rates of hepatitis B, hepatitis C and HIV infection may be representative of the rates in some other urban teaching hospitals in Canada, variation can be expected because of differences in the patient populations served. There is clearly a need for prevalence studies in other Canadian centres. These data would be of value not only for monitoring infection rates but also for evaluating the cost-effectiveness of potential prevention and management strategies. Finally, we believe that our results lend support to the use of universal precautions to protect health care workers from inadvertent exposure to bloodborne infective agents.
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We thank Robert Chua, Wayne Lau, Brian Mitchell and Rachelle Baillargeon for their technical assistance and Myrna Apanay for her secretarial services. We thank Abbott Laboratories and Ortho Diagnostics Systems for providing the serologic reagents.
References 1. Update: universal precautions for prevention of transmission of human immunodeficiency virus, hepatitis B virus, and other bloodborne pathogens in health-care settings. MMWR 1988; 37: 377-388 2. Universal precautions: report of a consensus committee meeting. Can Dis Wkly Rep 1989; 15: 23-28 3. Canadian Society of Laboratory Technologists: Position statement. Can JMed Technol 1990; 52: 2 4. Stewart CK, Walker PW: Clinical laboratory scientists' attitudes toward HIV testing in hospital environments. Clin Lab Sci 1991; 4:116-120 5. Board of Trustees, American Medical Association: Prevention and control of acquired immunodeficiency syndrome. JAMA 1987; 258: 2097-2103 6. Rhame FS, Maki DG: The case for wider use of testing for HIV infection. N Engl J Med 1989; 320: 1248-1254 7. St. Louis ME, Rauch KJ, Petersen LR et al: Seroprevalence rates of human immunodeficiency virus infection at sentinel hospitals in the United States. N Engl J Med 1990; 323: 213218 8. Gordin FM, Gibert C, Hawley HP et al: Prevalence of human immunodeficiency virus and hepatitis B virus in unselected hospital admissions: implications for mandatory testing and universal precautions. J Infect Dis 1990; 161: 14-17 9. Major CJ, Read SE, Coates RA et al: Comparison of saliva and blood for human immunodeficiency virus prevalence testing. J Infect Dis 1991; 163: 699-702 10. Federal Centre for AIDS Working Group on Anonymous Unlinked HIV Seroprevalence: Guidelines on ethical and legal considerations in anonymous unlinked HIV seroprevalence research. Can Med Assoc J 1990; 143: 625-627 11. Henderson DK, Fahey BJ, Willy M et al: Risk for occupational transmission of human immunodeficiency virus type 1 (HIV- 1) associated with clinical exposures: a prospective evaluation. Ann Intern Med 1990; 1 13: 740-746 12. Gerberding JL: Current epidemiologic evidence and case reports of occupationally acquired HIV and other bloodborne diseases. Infect Control Hosp Epidemiol 1990; 11 (suppl): 558-560 13. Kelen GD, Fritz S, Qaqish B et al: Unrecognized human immunodeficiency virus infection in emergency department patients. NEngl JMed 1988; 318: 1645-1650 14. Feinman SV, Krassnitzky 0, Sinclair JC et al: Prevalence and significance of hepatitis B surface antigen in a general hospital. Can Med Assoc J 1975; 112: 43-45 15. Arevalo JA, Washington AE: Cost-effectiveness of prenatal screening and immunization for hepatitis B virus. JAMA 1988; 259: 365-369 16. Antibody to hepatitis C virus in risk groups in Canada. Can Dis Wkly Rep 1990; 16: 23-25 17. Alberti A: Diagnosis of hepatitis C: facts and perspectives. J Hepatol 1991; 12: 279-282 18. Alter MJ, Gerety RJ, Smallwood LA et al: Sporadic non-A, non-B hepatitis: frequency and epidemiology in an urban U.S. population. J Infect Dis 1982; 145: 886-893 19. Kiyosawa K, Sodeyama T, Tanaka E et al: Hepatitis C in hospital employees with needlestick injuries. Ann Intern Med 1991; 115: 367-369
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