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Hepatitis C virus antibody prevalence among injecting drug users at selected needle and syringe programs in Australia, 1995-1997

Margaret A MacDonald, Alex D Wodak, Kate A Dolan and Philip H Cunningham
Med J Aust 2000; 172 (2): 57-61.
Published online: 17 January 2000
Research

Hepatitis C virus antibody prevalence among injecting drug users at selected needle and syringe programs in Australia, 1995-1997

Margaret A MacDonald, Alex D Wodak, Kate A Dolan,
Ingrid van Beek, Philip H Cunningham, and John M Kaldor,
for the Collaboration of Australian NSPs*

MJA 2000; 172: 57-61
For editorial comment see Watson

Abstract - Introduction - Method - Results - Discussion - Acknowledgements - References - Authors' details
- - More articles on Infectious diseases and parasitology


Abstract Objectives: To describe point prevalence of HCV antibody and relevant risk behaviour among people who inject drugs and who attended selected needle and syringe programs throughout Australia in 1995, 1996 and 1997.
Design and setting: Repeated cross-sectional surveys of one week's duration were carried out in 21, 20 and 23 needle and syringe program sites throughout Australia in 1995, 1996 and 1997, respectively.
Participants: All clients attending participating sites during the designated survey week were asked to complete a self-administered questionnaire and provide a finger-prick blood sample for HCV antibody testing.
Main outcome measures: Prevalence of HCV antibody.
Results:Survey response was 41% (n = 979) in 1995, 51% (n = 1463) in 1996 and 48% (n = 1699) in 1997. HCV prevalence declined significantly from 63% in 1995 to 51% in 1996 and 50% in 1997 (P < 0.001). Among respondents who reported injecting for less than three years, prevalence declined from 22% in 1995 to 13% in 1996 and 1997 (P < 0.001). Reported use of needles and syringes after someone else in the previous month declined from 31% in 1995 and 28% in 1996 to 15% in 1997 (P < 0.001).
Conclusions: Despite an apparent decline in HCV prevalence, carriage rates of HCV antibody remain high.


Introduction Hepatitis C virus (HCV) infection is predominantly spread through blood contact.1 In most First World countries, most prevalent and incident cases of HCV infection involve people who have, at some time, illicitly injected drugs. In such people, transmission is believed to occur predominantly through sharing of injecting equipment.2 HCV infection is a public health concern because of its serious complications, such as cirrhosis of the liver and hepatocellular carcinoma,3 as well as its high prevalence, long latent period and high probability of long-term carriage and infectiousness.

Australia adopted a harm reduction approach as part of its national drug strategy in 1985.4 An extensive network of needle and syringe programs (NSPs) has been established in Australia; in the financial year 1994-95, around 700 NSPs distributed six million syringes nationally and an additional four million were distributed through pharmacies.5 Early and vigorous implementation of harm reduction measures, such as methadone maintenance, peer-based education and NSPs, has successfully maintained low seroprevalence of HIV infection among people who inject drugs in Australia.6 In contrast, prevalence and incidence of HCV infection among this population remain high.2,7

To assess the impact of prevention activities on HIV and HCV infection, a monitoring system was established at selected NSPs throughout Australia.6 Cross-sectional surveys at NSPs among people who inject drugs offer a practical and repeatable mechanism for recruiting large samples of injecting drug users. This provides a basis for systematic monitoring of HCV and HIV infection, and of injecting behaviours associated with transmission of these viruses. We report the results of the first three years of national HCV monitoring among NSP attenders in Australia.


Methods The survey methods have been described in detail previously.6 Briefly, trained staff at participating NSPs asked all clients attending during one-week periods in March 1995, June 1996 and October 1997 to complete a brief, self-administered questionnaire and provide a finger-prick blood sample. Participating NSP sites were selected for number of attendances and coverage of all Australian States and Territories (see Box 1). Those selected in 1995 distributed approximately 40% of the syringes distributed nationally through NSPs. There was some change in sites over the three years because the number of NSPs increased, but a core group of 16 sites was maintained.

Sex and age group were recorded for all clients who attended participating sites during the survey week. As some clients attended more than once, a record was kept as to whether the attendance was the first for that week to measure survey response rate. Participants completed a brief questionnaire on basic demographic characteristics and injecting and sexual behaviour.

Capillary blood was collected on blotting paper by finger prick with single-use lancets. Venous blood was not obtained, as few NSPs had appropriate facilities for collecting and storing large amounts of blood. Specimens were tested for HCV antibody by a modified third-generation enzyme immunoassay (Abbott HCV 3.0, Chicago, USA). A modified cutoff value for optical density was calculated to capture more than 95% of the seronegative population. Specimens were considered positive for HCV antibody if the optical density to cutoff ratio was greater than or equal to one on initial and subsequent testing. In 1998, as a quality control measure, 60 samples were randomly selected from each year's survey and retested for HCV antibody as described. Retest results were 100% concordant for the 1995 and 1997 surveys but only 88% for 1996. Subsequently, all available stored 1996 samples (83%) were retested.

Ethical approval for this study was obtained from relevant ethics committees associated with the investigators and with participating sites.

Statstical analysis
Data were analysed with the Stata computer package.8 We assessed change in demographic, behavioural or serological variables using the χ2 test for categorical variables and the Kruskal-Wallis or Mann-Whitney tests for discrete variables. To control for changes in sample characteristics between surveys, we assessed change in HCV prevalence from 1995 to 1997 for all participants, and, for participants who reported only one or two years of drug injection, by multivariate logistic regression analysis. We also used multivariate logistic regression analysis, restricted to sites that participated in all surveys, to assess change in HCV prevalence.

Associations between HCV prevalence and participants' characteristics were evaluated by the χ2 test and χ2 test for linear trend. To control for intralaboratory variation with HCV antibody tests, we calculated HCV prevalence for 1996 participants using retested results where available. In addition, for participants with insufficient stored sera for retesting, the original estimates of HCV prevalence were adjusted for each category of variables used in the analysis, by the overall difference between original and retest test results. Associations between HCV prevalence and participants' characteristics in 1997 were also assessed using multivariate logistic regression. Factors significantly associated with HCV infection on univariate analysis (with an inclusion criterion of P ≤ 0.05) or factors that were considered a priori to be predictors of HCV risk were included in the logistic regression model.


Results
Characteristics of respondents
As shown in Box 1, 979 clients in 1995, 1463 in 1996 and 1699 in 1997 completed a questionnaire and provided a blood sample suitable for HCV antibody testing, giving overall response rates of 41%, 51% and 48%, respectively. There was a higher response rate among clients aged less than 25 years compared with those aged 25 years or more in 1996 (56% v. 49%), but no difference in 1995 and 1997. There was a higher response rate among females than males in 1995 (46% v. 39%) and 1997 (63% v. 39%).

The age ranges for respondents in the three years were 14-54 years in 1995, 13-53 years in 1996 and 15-58 years in 1997. The median age of respondents was significantly higher in 1995 than in 1996 (29 years v. 28 years; P = 0.009) and 1997 (29 years v. 27 years; P < 0.001). Median age at commencement of injecting drug use was 18 years in the three surveys. Consequently, the median number of years that respondents had injected drugs was significantly higher in 1995 than in 1996 (10 years v. 8 years; P = 0.001) and 1997 (10 years v. 7 years; P < 0.001).

Similar proportions of males (65%, 67% and 66%), respondents reporting being heterosexual (79%, 78% and 79%), and those reporting having been imprisoned in the past year (15%, 13% and 14%) participated in the 1995, 1996 and 1997 surveys. Almost a third of respondents in each year reported no contact with health services such as counselling, detoxification or methadone maintenance treatment. The proportion of respondents on methadone treatment, however, was significantly lower in 1997 (33%) than in 1995 (40%; P = 0.001) or 1996 (36%; P = 0.02).

More respondents reported that heroin was the last drug they injected in 1996 and 1997 than in 1995 (53% and 56% v. 44%) and fewer reported last injecting amphetamines (19% and 18% v. 21%) and methadone (12% and 11% v. 19%; P < 0.001). Daily or more frequent injection increased from 41% of respondents in 1995 and 1996 to 51% in 1997 (P = <0.001).

Syringe use after someone else
Reported use of a needle and syringe after someone else in the preceding month declined significantly from 1995 and 1996 to 1997 (31%, 28%, and 15%, respectively; P < 0.001). This practice was significantly more common among females than males in 1995 and 1997 (35% v. 28% and 17% v. 14%; P = 0.04).

In 1997, respondents aged

less than 25 years were more likely than older respondents to report syringe use after someone else in the past month (19% v. 12%; P = 0.001).

HCV antibody prevalence
Box 2 shows that HCV antibody prevalence was significantly lower in 1996 and 1997 than in 1995 (51% and 50% v. 63%; P < 0.001). This difference remained significant after adjustment for differences in sample characteristics between surveys (adjusted odds ratio, 0.5; 95% CI, 0.4-0.7). Sex, age, duration of drug injecting, last drug injected, frequency of drug injection and health service contact were included in the model. A similar pattern was found when analysis was restricted to the 16 sites that participated in all three surveys (63% in 1995 v. 50% in 1996 and 51% in 1997; P < 0.001) and when respondents who reported participation in more than one survey were excluded from the analysis (63% v. 49% and 47%; P < 0.001).

HCV antibody prevalence was also significantly lower in 1996 and 1997 (13%) than in 1995 (22%) among respondents who reported less than three years of drug injection (P = 0.03). This difference also remained significant after adjustment for sex, age, last drug injected, frequency of drug injection and health service contact (adjusted odds ratio, 0.4; 95% CI, 0.2-0.7). HCV antibody prevalence was lower in 1996 and 1997 than in 1995 among respondents aged less than 25 years, regardless of whether the last drug injected was heroin (trend test, P = 0.03) or amphetamine (trend test, P = 0.002; Box 3a).

Box 3b shows that, when respondents were grouped according to the year they started injecting, HCV antibody prevalence was higher among those reporting most recent injection of methadone or heroin than among those reporting most recent injection of amphetamine. HCV antibody prevalence was also significantly higher among respondents from New South Wales and Victoria than those from Queensland, and remained higher when the analysis was restricted to respondents reporting heroin as the last drug injected and stratified according to the year drug injection started (Box 3c). Multivariate logistic regression analysis showed that other factors significantly associated with presence of HCV antibody in 1997 included being female, having been imprisoned in the past year, having a history of methadone treatment, being aged 25 years or more, having injected drugs for more than five years, and daily or more frequent injection (see Box 2).


Discussion Our findings indicate that HCV antibody prevalence, although high, is declining, particularly among participants new to injecting. While all cases of HCV infection among respondents who reported having injected for only one or two years cannot be classified as new infections, it is highly likely that the vast majority reflect recent transmission.

Variation in the populations surveyed in the three years of the study cannot be excluded as an explanation for our observations. Respondents in 1997 were younger and newer to injecting than in 1995. Nonetheless, the decline in HCV antibody prevalence remained statistically significant when multivariate logistic regression analysis was used to control for differences in demographic characteristics, when analysis was restricted to respondents who reported less than three years of drug injection, and when analysis was restricted to sites that participated in all three surveys.

It is also conceivable that HCV infection status influenced participation in the survey. For example, people infected with HCV might be more likely to participate than those not infected because of the services provided by NSPs or because they have an interest in blood-borne infections by virtue of having one. Alternatively, people with HCV infection might be reluctant to provide a blood sample in a non-clinical setting because of concerns about inadvertent spread of infection. It is not possible to determine whether people with HCV infection were more or less likely than those without infection to participate in the surveys. If such bias occurred it is unlikely that the direction changed from 1995 to 1996 and 1997. However, the extent to which the magnitude of such bias may have changed over the three surveys is not known.

Comparison of our data with those of other Australian studies reporting HCV antibody prevalence according to type of drug injected and duration of injecting supports our observation that HCV antibody prevalence is declining among people who inject drugs. Among opiate injectors who had been injecting for less than three years, HCV antibody prevalence was 70% in the late 1980s9 and almost 50% in the early 1990s,10 compared with 20% in our study. Declining HCV antibody prevalence has also been reported from other cities that implemented HIV prevention measures in the mid-1980s, namely Geneva11 and Glasgow.12

We also found that the proportion of respondents who reported using a syringe after someone else was significantly lower in 1997 than in 1995 and 1996. There has been a marked decline in reported sharing of syringes in Australia since 1984, when more than 90% of respondents reported having done so in the month before interview.13 Of concern was the higher rate of sharing reported among respondents aged less than 25 years than among older respondents in 1997. Younger injecting drug users are probably more recent initiates to injecting; this is a subpopulation previously identified as being at extremely high risk of acquiring HCV infection.14 An extremely high incidence of HCV infection has also been reported recently among young people with a history of drug injecting in Sydney.7

It is difficult to explain the marked geographic variation in HCV antibody prevalence detected in our study. The sample recruited from Queensland was significantly different from other States and Territories with regard to known correlates of HCV infection such as duration of injecting and type of drug injected. Nonetheless, significantly lower prevalence persisted among respondents from Queensland compared with those from New South Wales and Victoria when the sample was stratified according to these factors.

Despite our finding of declining HCV antibody prevalence among people who inject drugs in Australia, and even though an epidemic of HIV infection has so far been prevented, the prevalence and incidence of HCV infection in this group remain high.2,7 Percutaneous transmission is more efficient for HCV than for HIV infection.1 More importantly, the carriage rate of HCV among injecting drug users was already considerably higher than that for HIV when harm reduction policies were first introduced.9 It is likely that occasional instances of shared injection equipment and other blood contact during injection have been sufficient to maintain high levels of HCV transmission without an increase in HIV transmission.

It can not be assumed that the results of our surveys are generalisable to all people who inject drugs in Australia. However, NSP clients represent a heterogeneous population of injecting drug users who are readily accessible for targeted prevention initiatives. Prevention efforts encompassing education, drug treatment and needle exchange need to be enhanced to improve consistency and coverage so that transmission of HCV infection is reduced further and the current low prevalence of HIV infection is sustained.


* The Collaboration of Australian NSPs: ACT Drug Referral and Information Centre (Maureen Cane); AIDS Council of Central Australia (Sue Fielding); Australian IV League (Judith Byrne); Biala Alcohol & Drug Services (Margaret Holtham); Centre for Immunology, St Vincent's Hospital Sydney (Phillip Cunningham & Claire Temby); Clovelly Park, Norlunga, SAVIVE and Salisbury NSP, Adelaide; Drug Intervention Services Cabramatta (Sue Heard & Lisa Maher); GAIN (Richard Beckman & Diane Flint); Gold Coast Hospital (Dr Lynn Hawken); HIV and Sexual Health Services Cairns (Chris Barron & Mark Mills); Kirketon Road Centre & K2 (Dr Ingrid van Beek & Damian Hull); Macfarlane Burnet Centre for Medical Research (Dr Nick Crofts); Melbourne Inner Needle Exchange (Craig Mercer); Northern Rivers Health Service (Wendy Evans); Northern Territory AIDS Council (Charles Roberts); Resource & Education Program (IDU): Redfern & Canterbury (Julie Dixon & Anna Miraglia); St George NSP (Richard Sulovsky); St Kilda NSP (Simon Kroes); Sexual Health Services, Toowoomba (Bill Rutkin); SHARPS Melbourne (Sean Swift & Melissa Virtue); South Australian Drug and Alcohol Services Council (Dr Robert Ali & Bob Braithwaite); Tasmanian Council on AIDS and Related Diseases (Melinda Tonks); Tasmanian Users Health Support League (Stuart Williams); Wentworth NSP (Elizabeth O'Neil & Andy Hart); West Australian AIDS Council Inc. (Katrina Roberts & Samantha Nicholson); Western Australia Substance Users' Assoc. Inc. (Tamara Speed); Western Region AIDS and Hepatitis Prevention (Sandra Fox); Western Sydney AIDS Prevention Services: Harris Park & Blacktown (Anton Evers).



Acknowledgements
We acknowledge the contribution of survey participants, needle and syringe program staff and site coordinators who facilitated the surveys. We also thank Dr Greg Dore for his comments on earlier drafts. Surveys were funded by the Commonwealth Department of Health and Aged Care. The National Centre in HIV Epidemiology and Clinical Research is supported by the Commonwealth Department of Health and Aged Care through the Australian National Council on AIDS and Related Diseases and its Research Advisory Committee.


References
  1. MacDonald M, Crofts N, Kaldor J. Transmission of hepatitis C virus: rates, routes and cofactors. Epidemiol Rev 1996; 18: 137-148.
  2. Crofts N, Jolley D, Kaldor J, et al. Epidemiology of hepatitis C virus infection among injecting drug users in Australia. J Epidemiol Community Health 1997; 51: 692-697.
  3. Seeff LB. Natural history of hepatitis C. Hepatol 1997; 3 Suppl: 21S-28S.
  4. Blewett N. National Campaign against drug abuse: Assumptions, arguments, and aspiration. Canberra: AGPS, 1987. (NCADA Monograph No. 1.)
  5. Wodak A, Lurie P. A tale of two countries: Attempts to control HIV among injecting drug users in Australia and the United States. J Drug Issues 1996; 27: 117-134.
  6. MacDonald M, Wodak A, Ali R, et al, on behalf of the Collaboration of Australian Needle Exchanges. HIV prevalence and risk behaviour in needle exchange attenders: a national study. Med J Aust 1997; 166: 237-240.
  7. van Beek I, Dwyer R, Dore GJ, et al. Infection with HIV and hepatitis C among injecting drug users in a prevention setting: retrospective cohort study. BMJ 1998; 317: 433-437.
  8. Stata Statistics/Data Analysis [computer program]. Version 5.0. Texas: Stata Corporation, 1997.
  9. Bell J, Batey RG, Farrell GC, et al. Hepatitis C virus in intravenous drug users. Med J Aust 1990; 153: 217-273.
  10. Crofts N, Hopper JL, Milner R, et al. Blood-borne virus infections among Australian injecting drug users: Implications for spread of HIV. European J Epidemiol 1994; 10: 687-694.
  11. Broers B, Junet C, Bourquin M, et al. Prevalence and incidence rate of HIV, hepatitis B and C among drug users on methadone maintenance treatment in Geneva between 1988 and 1995. AIDS 1998; 12: 2509-2066.
  12. Goldberg D, Cameron S, McMenamin J. Hepatitis C antibody prevalence among injecting drug users in Glasgow has fallen but remains high. Commun Dis Public Health 1998; 1: 95-97.
  13. Crofts N, Webb-Pullman J, Dolan K. An analysis of trends over time in social and behavioural factors related to the transmission of HIV among injecting drug users and prison inmates. Evaluation of the National HIV/AIDS Strategy 1993-94 to 1995-96. Technical Appendix 4. Canberra: AGPS, 1996.
  14. Garfein RS, Vlahov D, Galai N, et al. Viral infections in short-term injection drug users: the prevalence of hepatitis C, hepatitis B, human immunodeficiency, and human t-lymphotropic viruses. Am J Public Health 1996; 86: 655-661.

(Received 1 Jun, accepted 16 Sep, 1999)


Authors' details
National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Sydney, NSW.
Margaret A MacDonald, BSocSci, DipEpidemiol, Senior Research Assistant.
John M Kaldor, PhD, Deputy Director.

Alcohol and Drug Services, St Vincent's Hospital, Sydney, NSW.
Alex D Wodak, FRACP, FAFPHM, Director.

National Drug and Alcohol Research Centre, University of New South Wales, Sydney, NSW.
Kate A Dolan, PhD, Senior Lecturer.

Kirketon Road Centre, Sydney, NSW.
Ingrid van Beek, MBA, FAFPHM, Director.

Centre for Immunology, St Vincent's Hospital, Sydney, NSW.
Philip H Cunningham, BAppSc, Senior Hospital Scientist.

Reprints: Ms M A MacDonald, National Centre in HIV Epidemiology and Clinical Research, Level 2, 376 Victoria Street, Darlinghurst, NSW 2010.
mmacdATnchecr.unsw.edu.au


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Box 1
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2: Hepatitis C virus antibody prevalence according to demographic and injecting characteristics (1995-1997), and multivariate logistic regression analysis (1997)

 

1995

1996

1997

CharacteristicNo. tested% with HCVNo. tested% with HCVNo. tested% with HCVAdjusted odds ratio (95% CI)

Total979631463 51169950-
Sex
   Male63963981 49‡111947*1
   Female32764467 56574552 (1.5-2.7*)
Imprisonment in previous year
   No82160*122448*145947*1
   Yes14678190 71234702.3 (1.6-3.5*)
Health service contact
   NSP only30032*483 17*53220*1
   Detoxification,
     counselling
12552 18338276351.4 (0.9-2.2)
   Past methadone
     maintenance
15779 2657132570 3 (1.9-4.6*)
   Current methadone
     maintenance
39584524 77563743.8 (2.5-5.8*)
 
1995

1996

1997

CharacteristicNo. tested% with HCVNo. tested% with HCVNo. tested% with HCVAdjusted odds ratio (95% CI)

Age at survey (years)
 <206528*138 18*18419*1
 20-2422639363 22440231.1 (0.6-1.9)
 25-2919863308 50368471.9 (1.0-3.4‡)
 30-3423775282 68290642 (1.0-3.8‡)
 35+246 8436381414 845.7 (2.9-11.0*)
Years of drug use
 <3131 22*24013*308 13*1
 3-5165 3528521345 261.3 (0.8-2.1)
 6-1020962309 51362442 (1.2-3.3†)
 >104568658081642 837.5 (4.4-13.0*)
Last drug injected
 Amphetamine20635*274 22*31218*1
 Heroin43167780 54951542.3 (1.4-3.7*)
 Combined drugs8572126 63104591.7 (0.8-3.5)
 Methadone18987169 82180783 (1.5-5.9†)
 Other6546109 45142462.1 (1.1-4.1‡)
 
1995

1996

1997

CharacteristicNo. tested% with HCVNo. tested% with HCVNo. tested% with HCVAdjusted odds ratio (95% CI)

Frequency of drug injecting
 Less than daily50761†745 49†70741*1
 Daily or more39968609 56867582 (1.5-2.7*)
 Not in last month704798 4111845-
Syringe use after someone else in the last month
 No624 62†96850*1284491
 Yes27971382 58220531.3 (0.9-2.0)
State or Territory
 Queensland30940*490 33*47929*1
 Victoria11853191 48436512.4 (1.6-3.5*)
 New South Wales41284497 71523702.2 (1.4-3.3*)
 Other14059285 50261461.6 (1.0-2.6‡)

NSP=needle and syringe program. *P<0.001; †P<0.01 and >0.001; ‡P<0.05 and >0.01.
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3: HCV antibody prevalence in relation to age, injecting habits and State or Territory.

 

Figure 3a
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Figure 3b
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Figure 3c
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Received 13 November 2018, accepted 13 November 2018

  • Margaret A MacDonald
  • Alex D Wodak
  • Kate A Dolan
  • Philip H Cunningham


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