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Evaluation of the impact of Dublin's expanded harm reduction programme on prevalence of hepatitis C among short-term injecting drug users

Bobby P Smyth, Eamon Keenan, John J O`Connor

Table 1
Period of commencement of injecting, duration injecting, age, sex, partner's injecting status, principal drug injected,
and employment status in relation to risk for hepatitis C among injecting drug users with injecting
histories of less than 25 months; univariate and multivariate analyses
Univariate Analysis
Multivariate Analysis
 
Number
Prevalence of anti HGV %
Number
p value †
Odds ratio (95% confidence intervals)
p value
Period when commenced injecting
Before January 1994 (pre-94 group)
172
64.5
1.0
1.0
After January 1994 (post-93 group)
181
40.3
0.37 (0.24, 0.57)
< 0.001
0.43 (0.27, 0.67)
< 0.001
Duration since commenced injecting (months)
1 to 12
216
44.4
1.0
1.0
13 to 24
137
64.2
2.25 (1.45, 3.48)
< 0.001
1.76 (1.10, 2.80)
0.017
Age (years)
   
Under 21
168
47.0
1.0
1.0
21 and over
185
57.7
1.54 (1.01, 2.34)
0.044
1.51 (0.98, 2.34)
0.061
Sex
   
Male
241
51.0
1.0
   
Female
112
54.5
1.15 (0.73, 1.8)
0.55
   
Sexual Partner's injecting status
Partner injecting
109
53.2
1.0
   
No Partner injecting
236
52.1
0.96 (0.61, 1.51)
0.85
   
Primary drug injected
Heroin
274
52.2
1.0
   
Other
79
51.9
0.99 (0.60, 1.63)
0.96
   
Employment status
Employed
43
41.9
1.0
   
Unemployed
318
53.5
1.60 (0.84, 3.06)
0.15
   


*N=345, status of partner unknown for eight patients. Pearson X2 test

Injecting drug users represent a high risk group for hepatitis C virus (HCV) infection and, in many locations, the majority will test positive for antibody to HCV (anti-HCV) within two years of starting to inject.1 Although there is evidence of a reduction in rates of unsafe injecting, 2 3 there is little published research demonstrating that programmes that facilitate safe injecting have reduced the occurrence of HCV.4 Consequently, some commentators are not optimistic that we will see a decrease in HCV prevalence among injecting drug users.5

Harm reduction programmes include methadone treatment, education regarding safer injecting and the provision of syringe exchange. These services vastly expanded in Dublin over the period 1991 to late 1993. The number of community outreach workers and addiction counselors increased by 74%. We sought to test the hypothesis that, among injecting drug users with short injecting histories, the prevalence of HCV would be lower in those who started injecting during the period after this expansion in services.

The setting for this study was McCarthy Centre, which is the largest and longest established addiction treatment center in Dublin. Services provided include counselling, methadone maintenance and detoxification and assessment regarding medical problems associated with drug use such as HCV.

Patients, Method, and Results

Data have been recorded on an ongoing basis on the results of all HCV tests on injecting drug users attending Trinity Court since 1992. In this study, consecutive new attenders, resident in Dublin, with a reported injecting history less than 25 months, tested for anti-HCV between July 1993 and December 1996 were included. We used a third generation enzyme linked immunosorbent assay for anti-HCV (Ortho Clinical Diagnostics, Amersham, England). Positive results were confirmed with a further third generation test.
In all 353 injecting drug users were tested. The primary drug of choice was heroin for 78%, morphine sulphate for 21%, and benzodiazepines for 1%.

Those with injecting histories of less than 13 months were over-represented in the group that started injecting in the period after January 1994 (75.1% v 46.5%, x2 = 30.4, p<0.001). Period of commencement of injecting was not significantly associated with age, sex, employment or injecting status of sexual partner (x2 tests).

The prevalence of anti-HCV was 52.1%. Univariate analysis showed that those who started injecting in the period after January 1994 (post-1993 group) and those with injecting histories of less than 13 months demonstrated significantly reduced risks of HCV infection (see table 1). Age over 21 years was weakly associated with increased risk.

Table 2
Association between period of onset of injecting drug use and risk of hepatitis C, adjusted within strata of duration of injecting drug use

Commenced
injecting before Aug 93
Commenced injecting
between Aug 93 and July 94
Commenced
injecting after July 94
 
 
Number
Prevalence of anti HGV %
Number
Prevalence of
anti HGV %
Number
Prevalence of
anti HGV %
p value *
 
125
64.8
112
51.8
116
38.8

< 0.001

Stratified by duration injecting (months)
1-12
48
60.4
73
46.6
95
34.7
0.003
13-24
77
67.5
39
61.5
21
57.1
0.33


* Mantel-Haenszel X2 test for trend

Nivariate analysis was repeated with data stratified by length of injecting history (data not shown). This demonstrated a significant reduction in HCV in the post-1993 group with injecting histories of less than 13 months (odds ratio 0.36, (95% confidence intervals 0.21, 0.64) p=0.001) but the reduction was not significant in those with injecting histories of 13 months and over (odds ratio 0.57, (95% confidence intervals 0.28, 1.20_ p=0.20). Multivariate analysis was then performed with the three variables that were significant on univariate analysis being entered into a logistic regression equation. This resulted in a weakening of the association with duration since starting injecting (see table 1). Also the effect of age became of borderline significance. There was no evidence of interaction between independent variables.

To further explore for the presence of a trend of reducing prevalence of HCV, subjects were ranked chronologically in terms of their date of commencement of injecting and then divided into thirds - that is, those who began injecting before August 1993, those who started between August 1993 and July 1994 inclusive, and thirdly, those who first injected after July 1994. Table 2 shows the highly significant downward trend in HCV prevalence. When data are stratified by length of injecting history, the trend remains one of reducing HCV prevalence over time in both those with short and longer injecting careers. However, the fall in prevalence is statistically significant only in those with injecting histories of less than 13 months.


practices after the service expansion. Unfortunately, we were unable to control for other factors that may explain this decline in HCV. Alternatively explanations might include a possible reduction in overall injecting frequency among the more recent injectors or continued rates of unsafe injecting but confined within safer groups. Therefore, while acknowledging that our detection of a declining prevalence of HCV infection after an expansion in harm reduction services does not conclusively prove causality, we believe that this is an encouraging finding. However, we consider it premature to assume that this protective effect will persist over time, as a reduced rate of unsafe injecting by people within this group could still lead to a very high prevalence of HCV infection.5 It may simply take longer to do so.

We wish to thank Drs E O'Callaghan, J Barry, C Moran, and Z Johnson for their advice and criticism in the preparation of the manuscript. We also wish to acknowledge the staff at the Virus Reference Laboratory, Dublin, where all blood tests were analysed.

Funding: none.
Conflicts of interest: none.

1 Garfein RS, Vlahov D, Galia C, et al. Viral infections in sort-term injectin drug users: The prevalence of the hepatitis C, hepatitis B, human immunodeficiency, and human T-lymphocyte viruses. Am J Public Health 1996;86:655-61.
2 Robertson JR, Ronald PJM, Raab GM, et al. Deaths, HIV infection, abstinence, and other outcomes in a cohort of injecting drug users followed up for 10 years. BMJ 1994;309:369-72.
3 Hunter GM, Donoghoe MC, Stimson GV, et al. Changes in injecting risk befavious of injecting drug users in London 1990-1993. AIDS 1995;9:493-501.
4 Hagan H, Des Jarlais DC, Freidman SR, et al. Reduced risk of hepatitis B and hepatitis C among infection drug users in the Tacoma sytinge exchange program. Am J Public Health 1995;85:1531-7.
5 Wodak A, Crofts N. Once more unto the breach: controlling hepatitis C in njecting drug users. Addiction 1996;91:181-4.

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