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| BMJ
2000;321:78-82 ( 8 July )
Papers Prevalence of antibodies to hepatitis B, hepatitis C, and HIV and risk factors in Irish prisoners: results of a national cross sectional surveyShane Allwright a Department of Community Health and General
Practice, Trinity College, Dublin 2, Republic of Ireland, b Department
of Public Health, Eastern Regional Health Authority, Dr Steevens'
Hospital, Dublin 8, Republic of Ireland, c Hepatitis
and Retrovirus Laboratory, PHLS Central Public Health Laboratory,
London NW9 5HT
Correspondence to: S Allwright sllwrght@tcd.ie
Objectives: To determine the prevalence of antibodies to
hepatitis B core antigen, hepatitis C virus, and HIV in the prison
population of the Republic of Ireland and to examine risk factors
for infection. A high proportion of prisoners in many countries inject drugs.1-5 In the Republic of Ireland it has been estimated that 40% of prisoners misuse drugs.6 Given the association between injecting drug use and infection with hepatitis B virus, hepatitis C virus, and HIV, it is important to know both the prevalence of these infections and the pattern of risk behaviours in prison environments so that appropriate responses can be instituted. We report the results of a national study examining the relations
between self reported risk behaviour and the prevalence of
antibodies to hepatitis B core antigen, hepatitis C virus, and
HIV in the Irish prisoner population. At the time of our study there were about 2680 prisoners in the Republic of Ireland in 15 prisons. On the basis of information from the Department of Justice, Equality and Law Reform, prisons were categorised according to expected prevalence for blood borne viral infections into low, medium, and high risk prisons. The three low risk prisons were excluded from the survey as the total number of prisoners concerned (275) was too small to provide accurate estimates of prevalence or to preserve confidentiality. We estimated that a sample of 1200 prisoners was required to measure the prevalence of antibodies to hepatitis C virus in the high and medium risk prisons. All five high risk prisons were selected for the survey, and four of the seven medium risk prisons were selected at random. In six prisons all inmates were surveyed, while in the three larger high risk prisons half the population was selected by using systematic random sampling. Prisoners who were absent from the premises at the time of the survey (n=36) and prisoners considered to be a safety risk for the research staff (n=9) were excluded. The survey was carried out between September and November 1998. Staff and prisoners were briefed in advance. There were two parts to the survey: a questionnaire and collection of an oral fluid sample. Researchers met groups of 10 to 40 prisoners. The survey was explained, and prisoners were advised that the survey was voluntary, anonymous, and confidential. Ten prisoners who did not want to provide a sample of oral fluid were asked to complete the questionnaire. No inducements were offered and no negative sanctions were imposed on non-respondents. Prisoners who did not want to meet the researchers in a group setting were approached individually. No identifier was recorded on either the questionnaire or the oral fluid specimen. Once completed, the questionnaire and specimen were placed in a sealed envelope. A number was later assigned to both, linking the two. On the day of the survey anonymised information on age and sex was gathered on the entire population of each prison to assess the representativeness of the sample. Questionnaire - The questionnaire, derived from one used in several cross sectional prison surveys in the United Kingdom,7-11 consisted of questions relating to demography, prison sentences, risk behaviours, self reported hepatitis and HIV testing, and hepatitis B vaccination. It was self administered and took about five minutes to complete. A researcher helped those who had literacy difficulties. Oral fluid tests - Oral fluid samples were collected with a proprietary device (EpiScreen, Epitope, Beaverton, OR), refrigerated, and transported in batches by same-day courier to the laboratory. Processing (blind to demographic information) started the next working day. Each sample was tested for total IgG to check specimen quality. The sensitivity of the assay for antibodies to hepatitis B core antigen was estimated to be 82% and specificity greater than 99%. For the hepatitis C virus assay, sensitivity was estimated to be 80% and specificity 100%. For the HIV assay, both sensitivity and specificity were greater than 99%. (See the Appendix for details of testing procedures and estimation of sensitivity and specificity.) Statistical analysis - Data
were entered with an automated procedure12
and checked manually. Statistical analysis was carried out with
JMP.13 For categorical measures All nine prisons agreed to participate, and 1205 (88%) of the 1366 selected prisoners responded to the survey, representing 45% of the total Irish prison population at the time. Of the 72 women in prison on the survey days, 57 participated. Analyses refer to the 1193 participants who provided oral fluid samples that could be analysed or, for analyses relating to injecting drug use, to the 1178 respondents who declared their injector status. Denominators vary because not all respondents answered all questions. The median (range) age of respondents was 25 (16 to 67)
years. The age distribution of respondents was similar to that of
the total population of the surveyed prisons ( Prevalence of viral antibodies
Reported drug use One fifth of the injecting drug users (104) reported injecting drugs for the first time while in prison. Of 492 injecting drug users, 347 (70.5%) reported sharing needles while in prison compared with 225 (45.7%) in the month before imprisonment (P<0.0001). Of 330 injectors who had been in prison for more than three months on the current sentence, 148 (44.9%) stated that they had injected drugs in the previous month (in prison). Of 497 injectors, 185 (37.2%) reported being on a methadone programme before committal. Most of them (80%) reported injecting in the month before imprisonment. Sexual activity Hepatitis B vaccination Logistic regression In relation to both antibodies to hepatitis B core antigen and antibodies to hepatitis C virus the most important predictor of being positive was a history of injecting drug use (table 2). Those who reported injecting drugs were 81 times more likely to have antibodies to hepatitis C and 22 times more likely to have antibodies to hepatitis B than non-drug using prisoners. Although inferences from the antibodies to HIV regression model are limited by small numbers, those who reported a history of anal sex were eight times more likely to have positive results and those who reported injecting drug use three times more likely (table 2).
Separate models were constructed for respondents with and without a history of injecting drug use. Table 3 shows the model for hepatitis C in injecting drug users. Those in prison for more than three of the past 10 years, those who first injected three or more years ago, those who reported sharing needles in prison, and those who reported frequent current injecting were more likely to be positive for antibodies to hepatitis C virus. (Five tables of results of other models are shown on the BMJ website.) Antibodies to hepatitis B core antigen were more common in older injecting drug users, those who had been injecting longer, and those who reported having been treated for sexually transmitted infections. Antibodies to HIV were more common in older injectors and were associated with condom use.
In the models for respondents without a history of injecting drug
use, positive results for antibodies to hepatitis B core antigen
were more likely in older respondents and in men who reported taking
part in anal sex. Smoking heroin and being positive for antibodies
to hepatitis B core antigen were risk factors for hepatitis C. Reporting
anal sex with men was a powerful predictor of HIV in
non-injectors (odds ratio 56.0, 95% confidence interval 9.1 to
349.0). In this national representative survey two fifths of Irish prisoners reported a history of injecting drug use. A remarkable finding is that 21% of prisoners who use drugs reported that they had started to inject while in prison. Surveys in some Scottish prisons have reported similarly high figures, 9 11 14 but elsewhere the proportion who start injecting drug use in prison is much lower. 10 11 14 Clearly, providers of health care in Irish prisons need to focus preventive efforts in this area. Nearly half of those with a history of injecting drug use reported continuing use while in prison, and almost three quarters had shared injecting equipment in prison. These figures confirm a previous Irish prison report.4 Given the limited access to injecting equipment in prison and the high prevalence of infection, it is hardly surprising that sharing needles in prison emerged as a significant risk factor for hepatitis C in injectors (see table 3). The prevalence of infection with HIV was 2%, and 8.7% of prisoners had evidence of non-vaccine induced antibodies to hepatitis B. The HIV prevalence is similar to that reported in prison studies from other developed countries. 8 9 15 16 The prevalence of antibodies to hepatitis B core antigen in Irish prisons is similar to that in the United Kingdom, despite the higher proportion of injecting drug users in Irish prisons, and much lower than the 33% figure reported from Australia.3 The policy in the Republic of Ireland is to offer vaccination to all prisoners with sentences of eight months or longer. Although there is room for improvement (26.2% of prisoners reported completed vaccination), vaccine uptake is higher than in other prison populations and in other populations of injecting drug users.17 The unexpectedly low prevalence of hepatitis B suggests that the targeting of prisoners as a special group in Irish vaccination policy may be having some effect. More than a third of all prisoners, and more than 80% of injecting drug users, were positive for antibodies to hepatitis C virus. Community surveys among Irish injectors have indicated a prevalence of between 52% and 76%.18 The prevalence of antibodies to hepatitis C virus in Irish prisoners is similar to that found in Greek prisons1 but higher than that reported for Scotland19 and Australia.20
This cross sectional survey was not designed to provide direct evidence of transmission of infectious diseases in prison. Participants who spent more time in prison over the past 10 years, however, and those who shared needles while in prison were significantly more likely to be positive for antibodies to hepatitis C virus. This could be because the more chaotic users, who are more likely to be infected, spend longer in prison, but it also suggests that being in prison in Ireland may be an independent risk factor for contracting hepatitis C infection. In any case, it is clear that both injecting drug use and infection with hepatitis C virus are major problems that need to be examined by the healthcare system in Irish prisons. Community drug treatment services in Ireland have evolved considerably over the past decade and needle exchange and methadone maintenance are widely available. The Irish prison healthcare system has not kept pace with this change but is not unique in this as few prison healthcare services have implemented such measures. 5 21 Our survey suggests a need to consider increased provision of measures to reduce harm in Irish prisons. In addition, uptake of hepatitis B vaccination, although higher than in many countries, could still be improved. In Ireland, as elsewhere, injecting drug use in prison is here to
stay. The time has come for policy makers, researchers, and
clinicians working in prisons to ensure that being in prison does
not add unnecessarily to the health risks of this already disadvantaged
population.
We thank Geira Baruda, Marlen Carvalho, Tara Conlon, Derek Duggan, Emer Feely, Killian Forde, Carrie Garavan, Anne Halpin, Deirdre Handy, Derval Igoe, Frank Lule, Geraldine McCullough, Paul McKeon, Mary McSweeney, Ailbhe Mealy, Louise Mullen, Joan O'Donnell, Tom O'Dowd, Jill O'Leary, Hilda O'Neill, Patrick O'Sullivan, Sheilagh Reaper-Reynolds, Eimear Simms, and Aregay Woldegebriel, who helped with the fieldwork. We also thank the governors and staff of all the prisons visited and especially the prisoners who participated in this study; Linda Donovan and Josephine Morris at the Public Health Laboratory Service, London, for laboratory testing; and Noel Gill and Andrew Weild for their generous support and sharing of information. Finally, we thank Alan Kelly of the department of community health and general practice, Trinity College, Dublin, for statistical advice.
Contributors: SA, JB, FB, and LT developed the protocol and tendered for funding. SA, JB, FB, JL, and LT were involved in fieldwork and contributed to the analysis plan. SA supervised the data collection and carried out the analysis with JL. LT negotiated the contract for oral fluid analysis with the Pubic Health Laboratory Service as principal liaison between the Dublin team and the service. JVP supervised the development of laboratory methods and the laboratory analysis and wrote the Appendix . SA, JB, FB, JL, and LT contributed to the government report on which the paper is based. FB drafted the paper, with contributions from all authors. SA, FB, and JL wrote the revised version, with contributions from all authors. SA is guarantor for the paper.
Footnotes Funding: Department of Justice, Equality and Law Reform, Republic of Ireland. Competing interests: FB has contributed to policy development on prison health for the Labour party and, until recently, was a part time prison medical officer. JB is a member of the National Drugs Strategy Team. Though the study was funded by Department of Justice, Equality and Law Reform, Republic of Ireland, the research contract guaranteed freedom to publish results in a peer reviewed journal. Extra tables of results can be found on the BMJ's website
Oral fluid testing procedures Estimation of sensitivity and specificity of oral
fluid tests
References
(Accepted 30 March 2000)
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tests were used to compare groups. Multiple logistic regression analysis
was used to identify factors associated with positive test
results.