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
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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.
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| 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).
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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).
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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.
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* 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 |
- MacDonald M, Crofts N, Kaldor J. Transmission of hepatitis C virus:
rates, routes and cofactors. Epidemiol Rev 1996; 18:
137-148.
-
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.
-
Seeff LB. Natural history of hepatitis C. Hepatol 1997; 3
Suppl: 21S-28S.
-
Blewett N. National Campaign against drug abuse: Assumptions,
arguments, and aspiration. Canberra: AGPS, 1987. (NCADA Monograph
No. 1.)
-
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.
-
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.
-
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.
-
Stata Statistics/Data Analysis [computer program]. Version 5.0.
Texas: Stata Corporation, 1997.
-
Bell J, Batey RG, Farrell GC, et al. Hepatitis C virus in intravenous
drug users. Med J Aust 1990; 153: 217-273.
-
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.
-
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.
-
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.
-
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.
-
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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2: Hepatitis C virus antibody prevalence according to demographic and injecting characteristics (1995-1997), and multivariate logistic regression analysis (1997) | | 1995
| 1996
| 1997
| Characteristic | No. tested | % with HCV | No. tested | % with HCV | No. tested | % with HCV | Adjusted odds ratio (95% CI) |
| Total | 979 | 63 | 1463 | 51 | 1699 | 50 | - | Sex | Male | 639 | 63 | 981 | 49 | 1119 | 47* | 1 | Female | 327 | 64 | 467 | 56 | 574 | 55 | 2 (1.5-2.7*) | Imprisonment in previous year | No | 821 | 60* | 1224 | 48* | 1459 | 47* | 1 | Yes | 146 | 78 | 190 | 71 | 234 | 70 | 2.3 (1.6-3.5*) | Health service contact | NSP only | 300 | 32* | 483 | 17* | 532 | 20* | 1 | Detoxification, counselling | 125 | 52 | 183 | 38 | 276 | 35 | 1.4 (0.9-2.2) | Past methadone maintenance | 157 | 79 | 265 | 71 | 325 | 70 | 3 (1.9-4.6*) | Current methadone maintenance | 395 | 84 | 524 | 77 | 563 | 74 | 3.8 (2.5-5.8*) | | | 1995
| 1996
| 1997
| Characteristic | No. tested | % with HCV | No. tested | % with HCV | No. tested | % with HCV | Adjusted odds ratio (95% CI) |
| Age at survey (years) | <20 | 65 | 28* | 138 | 18* | 184 | 19* | 1 | 20-24 | 226 | 39 | 363 | 22 | 440 | 23 | 1.1 (0.6-1.9) | 25-29 | 198 | 63 | 308 | 50 | 368 | 47 | 1.9 (1.0-3.4) | 30-34 | 237 | 75 | 282 | 68 | 290 | 64 | 2 (1.0-3.8) | 35+ | 246 | 84 | 363 | 81 | 414 | 84 | 5.7 (2.9-11.0*) | Years of drug use | <3 | 131 | 22* | 240 | 13* | 308 | 13* | 1 | 3-5 | 165 | 35 | 285 | 21 | 345 | 26 | 1.3 (0.8-2.1) | 6-10 | 209 | 62 | 309 | 51 | 362 | 44 | 2 (1.2-3.3) | >10 | 456 | 86 | 580 | 81 | 642 | 83 | 7.5 (4.4-13.0*) | Last drug injected | Amphetamine | 206 | 35* | 274 | 22* | 312 | 18* | 1 | Heroin | 431 | 67 | 780 | 54 | 951 | 54 | 2.3 (1.4-3.7*) | Combined drugs | 85 | 72 | 126 | 63 | 104 | 59 | 1.7 (0.8-3.5) | Methadone | 189 | 87 | 169 | 82 | 180 | 78 | 3 (1.5-5.9) | Other | 65 | 46 | 109 | 45 | 142 | 46 | 2.1 (1.1-4.1) | | | 1995
| 1996
| 1997
| Characteristic | No. tested | % with HCV | No. tested | % with HCV | No. tested | % with HCV | Adjusted odds ratio (95% CI) |
| Frequency of drug injecting | Less than daily | 507 | 61 | 745 | 49 | 707 | 41* | 1 | Daily or more | 399 | 68 | 609 | 56 | 867 | 58 | 2 (1.5-2.7*) | Not in last month | 70 | 47 | 98 | 41 | 118 | 45 | - | Syringe use after someone else in the last month | No | 624 | 62 | 968 | 50* | 1284 | 49 | 1 | Yes | 279 | 71 | 382 | 58 | 220 | 53 | 1.3 (0.9-2.0) | State or Territory | Queensland | 309 | 40* | 490 | 33* | 479 | 29* | 1 | Victoria | 118 | 53 | 191 | 48 | 436 | 51 | 2.4 (1.6-3.5*) | New South Wales | 412 | 84 | 497 | 71 | 523 | 70 | 2.2 (1.4-3.3*) | Other | 140 | 59 | 285 | 50 | 261 | 46 | 1.6 (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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