Analysis of risk factors associated with hepatitis B and C infection in correctional institutions in British Columbia

The factors associated with infection with hepatitis B (hbv) and C viruses (hcv) were studied in residents of correctional institutions in British Columbia. Four hundred and fifteen residents volunteered to participate in this study. Among 415 residents tested, 28% were positive for hvb or hcv markers. Sixty-five per cent of the residents positive for hbv markers were also infected with hcv. However, in hbv-negative residents, only 14% were positive for antibody to hcv (anti-hcv). The highest rates for hbv and hcv were in 25- to 44-year-old residents. The analysis of risk factors and infection predictors in 354 residents showed that intravenous drug use and history of hepatitis were associated with infection with both hbv and hcv. The relative risk for hbv in intravenous drug users was 4.4 times that in nonusers; for hcv relative risk was 3.4 times. In the group with history of hepatitis, the relative risk was 6.2 and 4.5 times for hbv and hcv, respectively. The multivariate analysis of the data showed that both intravenous drug use and a history of hepatitis were significant (P<0.0001). Tattooing or history of transfusion was not associated with increased risk for hcv, but tattooing and age were significant factors for hbv.

Analyse des facteurs de risque associes a l'hepatite B et a l'hepatite C dans les etablissements correctionnels de Ia Colombie-Britannique RESUME : Les facteurs associes a !'infecti on au virus de l'hepatite Bet de l' hepatite C (IIBV et 11cv) ont ete etudies chez des p ri sonnicrs incarceres dans des etablisscments COITection nels de Ia Colombic-Britannique. Quatr e cent quinzc r esidents se sont partes vo lontaircs pour participcr a cclte etude.Pam1i les 415 reside n ts sou m is aux analyses.28 % sc sont reveles seroposi tifs a regard des mar queurs du vi rus de l'hepati te B ou C. Soixantc-c i nq pour cent des residents seroposi tifs a r egard des marqueurs du IIBV etaient egalemen t infectes au IICV .Toutcfois.chez lcs residents IIBV-negatifs.seu ls 14% Clai cnt positifs a l'egard de l'an ti cOI•ps anti-IICV.Les taux lcs p l us c leves a J'egard du IIBV ct du IICV Se trouvaicnt dans Ia tranc h e des 25 a 44 ans.L'analyse des facteu r s de r i sque et des p 1 •ed ictew•s de !'in fection chez 354 res idents a r evel e que Ia pri se de d r ogues in traveineu ses et l cs antecedents d 'hepatite etaicnt autant associ es a !'i nfecti on par IIBV q u e par IICV.Lc 1 •isq u e rel a ti f de IIBV chez lcs usagers de drogues i ntravc i ncuses Cla i t de T HE INTRODUCTION OF A NEW TEST FOR TH E DETECTION OF antibody to hepatitis C virus (anti-HCV) has allowed the study of infection with th is virus in different risk groups (l).A high prevalence of hepatitis C virus (H CV) infection has been reported in hemodia lysis patients (2).intravenous drug users (3) and hemophiliacs (4).Several studies (5)(6)(7)(8) have shown that there is a high prevalence of infection with hepatitis B virus (1-IBV) in residents of correctional institutions.Recent studies have also shown a high prevalence of infection with HCV in residents of correctional institutions (9)(10)(11).However, in these studies, the associa ted factors were not.investigated.
We re port here the analysis of the factors associated with the seroprevalence of HBV and HCV in residents of federal correctional institutions in British Columbia.

PATI ENTS AND METHODS
In 1989 Correctional Services of Canada implemented a hepatitis B immunization program for a ll inmates incarcerated in federal institutions.In the Pacific region (British Columbia and Yukon).where 14.4% of federal inmates are incarcerated , a seroprevalence study for viral hepatitis markers was undertaken as part of the immunization program.The initia l phase of the program was to provide the inmate popula tion with information on the potential short tem1 and long term effects of hepatitis B infection and the benefits of immunization.Information brochures we re distributed , a udiovisual presentations and group and individual counselling were given.In the first six months of the program, 23% of the popu lation accepted the invitation to participate in the immunization program.Infom1ed consent was obtained from all participants before immunization with h epatitis B vaccine and screening for viral h epatitis markers.Providing a blood sample or completion of a questionnaire designed to identify predictor (ie, history of hepatitis) and risk factors was not mandatory for immunization.The questionnaire requested information on history of hepatitis, blood transfusions, tattooing, intravenous drug use and sexual orientation .
Blood samples were obtained from 4 15 male residents of the federal correctional institutions in British Columbia .The number of residents tested from each age group and sampling rates a re given in Table 1.Samples were tested for hepatitis B surface antigen (H BsAg), antibody to core antigen (anti-HBc) and antibody to surface antigen (anti-HBs) by enzyme immunoassays (Abbott Laboratories, Illinois).These samples were stored at -70°C and later tested for a nti-I-ICV by enzym e 154 An individual was infected with HBV if h e or she was I-IBsAg-positive and/ or anti-HBc-positive.Individuals who were anti-I-IBs-positive only were not included in the infected group.A positive result for anti-HCV was d efined as a positive enzyme immunoassay plus a positive confirmatory test.Data were entered in a computer fil e without individual identifiers .Analysis was carried out using x 2 or multivariate analysis using logistic regression.

RESULTS
Four hundred and fifteen inmates consented to have blood drawn.There were 1806 eligible for the study (Table 1) .The questionnaires were completed by 354 (85.3%) of 415 participating residents.The sampling rates were similar for the older groups at 23 to 35% but lower in the 15 to 24 age group at 17% .Twelve residents (3.0%) were positive for 1-IBsAg (Table 2).The prevalence of I-I BV markers was 28%.None of the inmates had been immunized with 1-IBV vaccine to the a uthors' knowledge but three were positive for anti-1-IBs alone, which may represent immunization.
The prevalence of anti-HCV was also high, with 106 samples (25.5%) positive by both enzyme immunoassay and first generation RIBA 1-ICV tests.Of 10 samples that were indetenninate by first generation RJBA 1-ICV, nine were positive by second-generation RIBA; thus, the overall prevalence of anti-HCV was 28% in this population.
The distribution of markers (Table 2) showed that 259 residents were negative, 41 were 1-IBV-positive and HCV-n egative , 37 were anti-I-ICV-positive and HBV-n egative and 76 (65%) were positive for both.Results showed that residents positive for HBV or I-ICV a lone had somewhat different distributions of risk factors.Intravenous drug use was a risk factor in 76% of anti-I-ICV and 45% of II BV-positive resid ents.Tattooing was a risk factor for II BV (18%) but not for anti-IICV-positive (5%) residents .Transfusion was a small risk factor for anti-HCv-positive residents only (data not shown).
The positivity rate for HBV markers and anti-IICV for different age groups is given in Figure l.Resu lts showed that the rate for HBV (18%) and IICV (16%) was similar in the 15 to 24 year age group, with a small percentage (4% ) of individuals infected with both.In the 25 to 34 year age group, the infection ra tes for HBV.HCV and dua l infection were 30.32 and 22%.respectively.The rate for IIBV was further increased to 38% in the 35 to 44 year age group, whereas Lhe prevalence of anti -HCV (30% ) decreased somewhat and the prevalence rate for dual infection remained the same (21 %).However. the rates for both HBV (16%) and IICV (16%) were s ignificantly reduced in the 45 to 54 year age group.Dual infection was detected in 9% of the residents tested .There was a further decline in the prevalence of IIBV markers ( 13%) in residents 55 years of age or older.The prevalence of HCV (3%) was also s ignificantly reduced.The du a l infection rate in th is group was l % .
Of the 415 residents , 354 completed questionnaires regarding risk factors.Having a history of hepatitis was a strong predictor of having HBV m a rkers .(relative risk [RR]=6.2.95% confidence limits [CL] 3.5-11.2) or IICV markers (RR=4 .5 95% CL 2.6-8 .0)(Table 3).Of t11e risk factors measured.intravenous drug use had an RR of 4.4 (range 2.9 to 6.7) fo r HBV and 3.4 (range 2.7 to 4.3) for IICV.Tattooing had an RR of 1.5 (range 1.3 to 1.8) for IIBV a nd IICV.A h istory of transfusion was not a risk factor for either HBV or IICV (RR l.l and 1.0, respectively).Sexual preferences cou ld not be analyzed as a risk factor because the answers were ru led unreliable.
Mu ltivariate analysis using mu ltiple regression showed that intravenou s drug use , tattoos and age were all significantly associated witl1 HBV, in that order.while for HCV only intravnous drug use was significant in the model.

DISCUSSION
Results have shown a high prevalence of hepatitis B and C infection among residents of correctional institutions in British Columbia .The low response rate in our survey ind icates a major possib ili ty of response b ias.The prevalence of HBV and IICV must be interpreted ca utiously .The find ing that our rates were s im ilar to other studies helps to reduce concerns about tl1e response bias.
The comparison of risk factors s h ould be less biased as prior knowledge of HCV status wou ld not have been available to these individuals.Although a few may have known that they had had non-A.non-B hepatitis, this is less likely to have influ enced their decision to be tes ted.As this was part of an immunization program.the prevalences may be low because immunization was not available for those who had been infected previously.In spite of this.similar data have been reported previously by other investigators (5)(6)(7)(8) for HBV.Intravenous drug use has been found to be important for HBV infection (8.11 -13); however.the risk factors associated with HCV infection in residents of correctional institutions has not been fully explored.The comparison of risk factors for HBV-positive with those for HCV-posilive individua ls may give some information on the relative infectivity of routes of infection.
Twenty-eight per cent of residents were positive for anti-IICV.A similar prevalence rate (29.8%) was reported (9) from another institution in Canada.The risk fac tor associated with 1 -1cv infection is intravenous drug use.Intravenous drug use has been recognized previously as an important risk factor (14) for infection with 11cv.History of h epatitis was also a predictive factor for infection with HCV.However, the significance of this factor is that. in the event of an exposure to the blood of a person with history of h epatitis.that exposure is much more likely to be to HBV or 11cv than in an individual without such a history.at least in this population .
Transfusion.age and tattooing were not associated with increased risk for infection with HCV .A recent report (1 4 ) from the United States a lso indicated that the majority of HCV infections was not associated with transfusion.That transfusion is not a risk factor is possibly due to screening of blood donation for IICV .Our results indicate that there is a relationship between HBV and IICV transmission as 65% of HBV-positive residents we re a lso positive for HCV .Hence the screening for HBV has also reduced the risk for 11cv.The multivariate analysis showed that both intravenous drug use and history of h e patitis were significant for HCV infection (P<0.0001).
Another observation was of the coexistance of infection with HBV and HCV in a large proportion of residents (65%) tested.A similar finding was also reported from Alberta.where 58% of HBv-positive inmates were also positive for HCV (ll).
These results showed that HBV a nd HCV have some similar predictors such as intravenous drug use and history of h epatitis.However , some of the predictors are not shared, such as tattooing and age, which were risk predictors for HBV but not for HCV.A large proportion of anti-IICV-positive individuals carries the HCV virus (14 , 15) .Our results indicate that HCV may not be as infectious as 1 -IBV.The lack of an association wiU1 tattooing may indicate that needlestick exposures to 11cv a re not as likely to result in infection .The lack of association with age may indicate a cohort effect.but this also m ay be a m a rker for other risk factors such as sexual transmission.
Overa ll , the comparison of HCV with HBV risk predictors indicates that HCV is being transmitted to individua ls in correctional institutions and intravenous drug use is the major risk factor .Tattooing, as carried out in institutions.is a risk factor for HBVbut not HCV, indicating that 1-! CV may require larger amounts of fluid transfer for infection to occur and hence a lower risk of infection following needlestick eA.'])Osures .There is a need to clarifY the transmission routes for HCV in order to inform inmates a nd staff of potential risks.HCV appears to h ave similar risk factors to human immunodeficiency virus.

4. 4
fo is p l us eleve que Chez Jcs non -utilisateurs .Pou r Jc IICV.Jc risque rela ti f a l'egard du IIBV Clai t de 3.4 continued on next page CoTTeciional Ser vices of Canada.AbbolLsford.B1iLish Columbia: Laboratory for Viral Hepatitis.Bureau of Microbiology.LClboratory Centre for Disease Con trol.Health Canada.Ottawa: and Department of Health Care and Epidemiology.University of BriLish Columbia.Vancouver.B1•ilish Columbia COTTespondence and reprints: Or m< Chaudhary.Laboratory fo r Viral HepaULis.Bureau of M icrobiology.Laboratory Centre for D isease Control.Tunney's Pasture.Ottawa.Ontario l<lA OL2.Telep hone (613) 957-0 180 .Fax (613) 954 -0207 Received for p u blicaLion Decem ber 2 1. 1993.Accepted Ap1il 4. I 994 fois plus eleve .Dans le groupe presenlanl des antecedents d'he pa lile.le hsque rela lif Hail de 6.2 el de 4.5 fois.pour le HBV e l le HCV respectivem enl.L'a n a lyse a va~iabl es mu lliples des donnees a revele qu e. el les drog u es inlr avein e uses el les antecedents d 'h e pa lile eta ienl sign ifi califs (P<O.OOO 1).Le la louage au les anteced ents de Lransfusion n'onl pas ete assoc ies a un risqu e accm d e II CV .mais le lalouage et r age onl ete d es facle urs s ignificalifs a l'egard du IIBV.

TABLE 2
Prevalence and relationship of HBV markers and anti-HCV in the residents of Brisith Columbia correctional services

TABLE 3
Risk factors for HBV and HCV in correctional institutions Prevalence rates of hepatitis B (HB) uirllS.hepatitis C (HC) virus and both in different age groups of residents of British AuGusT 1994 CAN J INFECT D1s VoL 5 No 4 JuLv 1