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To Increase Investment in Syringe Exchange
in the U.S. would be Cost-saving.
Results from modelinghypothetical syringe coverage levels
INTL AIDS CONF โ WASHINGTON DC โ 23 JULY 2012
T.Q. Nguyen1, B.W. Weir1, S.D. Pinkerton2, D. Des Jarlais3, D. Holtgrave1
1Johns Hopkins Bloomberg School of Public Health, Department of Health, Behavior and Society
2Medical College of Wisconsin, Department of Psychiatry and Behavioral Medicine3Beth Israel Medical Center and North American Syringe Exchange Network
Acknowledgements
โข amFAR, The Foundation for AIDS Research (with funding from the Elton John Foundation and the Irene Diamond-Tides Foundation) for supporting the Beth Israel/NASEN survey
โข National Institute on Drug Abuse for supporting B.W. Weirโs training
โข Johns Hopkins School of Public Healthโ Sommer Scholars Program for supporting T.Q. Nguyenโs
trainingโ Department of Health, Behavior and Societyโ Student Conference Fund
โข Researchers and organizations that have contributed to research under this topic
โข Co-authors: Mr. Brian W. Weir, Dr. David Holtgrave, Dr. Don Des Jarlais and Dr. Steven Pinkerton
Federal HIV prevention budget
Total syringe
exchange programsโ
budgets
Ratio:41 to 1
There is a disconnectbetween injection drug usersโ (IDU) share in the HIV epidemic and funding for the effective intervention of syringe exchange.
New HIV infections in the US
heterosexual29%
IDU10%
MSM/IDU3%
MSM58%
Objective
To inform policy decisions, examine if increasing investment in syringe exchange programs (SEPs) would be cost-effective or cost-saving as an HIV prevention intervention.
Questions
What would happen to HIV incidence if SEP syringe supply were larger?
How much would it cost and how much would it save?
Study synopsis:
Analysis approach
Model HIV incidence due to injection risk
in hypothetical cases with higher SEP syringe coverage
than current level (base case)
Method based on Pinkertonโs model used in
Pinkerton, S.D. (2010). Is Vancouver Canadaโs supervised injection facility cost-saving? Addiction. 105:1429-1436
number of new HIV infections due to drug injection risk in a year
number of IDUs (full-year equivalent)
HIV prevalence among IDUs
number of injections with a receptively shared (aka โborrowedโ) syringe per IDU per year
proportion of syringes that are contaminated with HIV
probability of getting infected when using an HIV-contaminated syringe
๐ผ๐๐น๐ธ๐ถ๐๐ผ๐๐๐=๐๐๐ (1โ๐๐ ๐ธ๐ ) โ๐ต๐๐ ๐ ๐โ๐ถ๐๐๐๐ด๐ โ๐๐ ๐ด๐๐๐๐ ๐๐ต
number of injections with a receptively shared (aka โborrowedโ) syringe per IDU per year
number of new syringes from SEPs per IDU per year
number of new syringes from other sources per IDU per year
โค๐ฉ๐ถ๐น๐น๐บ+๐บ๐ฌ๐ท๐บ๐๐น๐บ๐๐๐๐+๐๐๐๐บ๐ฌ๐ท๐บ๐๐น๐บ๐๐๐๐
๐ฉ๐ถ๐น๐น๐บ+๐บ๐ฌ๐ท๐บ๐๐น๐บ๐๐๐+๐๐๐๐บ๐ฌ๐ท๐บ๐๐น๐บ๐๐๐
๐ฐ๐ต๐ญ๐ฌ๐ช๐ป๐ฐ๐ถ๐ต๐บ๐๐๐
๐ฐ๐ต๐ญ๐ฌ๐ช๐ป๐ฐ๐ถ๐ต๐บ๐๐๐๐
DERIVATION: Starting from equation for HIV incidence
number of new infections due to injection risk in a yearnumber of IDUs (full-year equivalent)HIV prevalenceprobability an uninfected IDU gets infected in the year๐ผ๐๐น๐๐ ๐๐ต=1โ (1โ๐๐ ๐ด๐๐๐๐ ๐๐ต )๐ถ๐๐๐๐ด๐๐ผ๐๐ฝ๐ โ๐ถ๐๐๐๐ด๐๐ผ๐๐ฝ๐ โ๐๐ ๐ด๐๐๐๐ ๐๐ตprobability of getting infected when using an HIV-contaminated syringenumber of injections using HIV-contaminated syringes per IDU per year
๐ถ๐๐๐๐ด๐๐ผ๐๐ฝ๐=๐ต๐๐ ๐ ๐ โ๐ถ๐๐๐๐ด๐number of injections with a receptively shared (aka โborrowedโ) syringe per IDU per yearproportion of syringes that are contaminated with HIV
๐ผ๐๐น๐ธ๐ถ๐๐ผ๐๐๐=๐๐๐ (1โ๐๐ ๐ธ๐ ) โ๐ต๐๐ ๐ ๐โ๐ถ๐๐๐๐ด๐ โ๐๐ ๐ด๐๐๐๐ ๐๐ต
(b/c borrowing is likely to decrease or stay the
same)
๐ผ๐๐น๐ธ๐ถ๐๐ผ๐๐๐h๐ฆ๐๐ผ๐๐น๐ธ๐ถ๐๐ผ๐๐๐๐๐๐ ๐
DERIVATION: Comparing hypothetical case and base case
Pinkerton based on Kaplan & OโKeefeโs simplified needle circulation model:๐ถ๐๐๐๐ด๐h๐ฆ๐
๐ถ๐๐๐๐ด๐๐๐๐ ๐ โค๐ต๐๐ ๐ ๐๐๐๐ ๐+๐๐๐ ๐๐๐๐ ๐
๐ต๐๐ ๐ ๐h๐ฆ๐+๐๐๐ ๐h๐ฆ๐
number of new syringes from SEPs per IDU per yearnumber of new syringes from other sources per IDU per year
โน๐ผ๐๐น๐ธ๐ถ๐๐ผ๐๐๐ h๐ฆ๐
๐ผ๐๐น๐ธ๐ถ๐๐ผ๐๐๐๐๐๐ ๐
โค๐ต๐๐ ๐ ๐๐๐๐ ๐+๐๐๐ ๐๐๐๐ ๐
๐ต๐๐ ๐ ๐h๐ฆ๐+๐๐๐ ๐h๐ฆ๐
๐ผ๐๐น๐ธ๐ถ๐๐ผ๐๐๐h๐ฆ๐
๐ผ๐๐น๐ธ๐ถ๐๐ผ๐๐๐๐๐๐ ๐
โค๐ต๐๐ ๐ ๐+๐๐ธ๐๐๐๐ ๐๐๐๐ ๐+๐๐๐๐๐ธ๐๐๐๐ ๐๐๐๐ ๐
๐ต๐๐ ๐ ๐+๐๐ธ๐๐๐๐ ๐h๐ฆ๐+๐๐๐๐๐ธ๐๐๐๐ ๐h๐ฆ๐
โค๐ถ๐๐๐๐ด๐h๐ฆ๐
๐ถ๐๐๐๐ด๐๐๐๐ ๐
number of new syringes per IDU per year
ยฟ๐ต๐๐ ๐ ๐h๐ฆ๐๐ต๐๐ ๐ ๐๐๐๐ ๐
โ๐ถ๐๐๐๐ด๐ h๐ฆ๐
๐ถ๐๐๐๐ด๐ ๐๐๐ ๐
ยฟ๐๐๐ (1โ๐๐ ๐ธ๐ ) โ๐ต๐๐ ๐ ๐h๐ฆ๐๐ถ๐๐๐๐ด๐ h๐ฆ๐ โ๐๐ ๐ด๐๐๐๐ ๐๐ต
๐๐๐ (1โ๐๐ ๐ธ๐ ) โ๐ต๐๐ ๐ ๐๐๐๐ ๐๐ถ๐๐๐๐ด๐ ๐๐๐ ๐ โ๐๐ ๐ด๐๐๐๐ ๐๐ต
Calculate:
Let vary: hyp case = proportion of drug injections โcoveredโ by new syringes from
SEPs
๐ผ๐๐น๐ธ๐ถ๐๐ผ๐๐๐h๐ฆ๐
๐ผ๐๐น๐ธ๐ถ๐๐ผ๐๐๐๐๐๐ ๐
โค๐ต๐๐ ๐ ๐+๐๐ธ๐๐๐๐ ๐๐๐๐ ๐+๐๐๐๐๐ธ๐๐๐๐ ๐๐๐๐ ๐
๐ต๐๐ ๐ ๐+๐๐ธ๐๐๐๐ ๐h๐ฆ๐+๐๐๐๐๐ธ๐๐๐๐ ๐h๐ฆ๐
parameter value sources/basis
i # full-year equivalent IDUs in US
1.23mbased on 1992-2002 IDU pop estimation from Brady et al. (2002), adjusted for cycling in/out of injecting (based on Galai et al., 2003)
ii # injections per IDU per yr
1023365.25 * number of injections per IDU per day (2.8 โ Lurie et al., 1998; Tempalski et al., 2008)
iii # injections with a borrowed syringe per IDU per yr
84.9based on probability of borrowing 8.3% (Pinkerton, 2011; Kaplan, 1993; consistent with NIDA CA data) & number of injections (ii.)
iv # new syringes per IDU per yr
187.6based on number of injections (ii.), number of borrows (iii.) & number of times an IDU uses a syringe he/she owns (5 โ Huo & Oullet, 2007)
v total # syringes from SEPs per yr
36.8mBeth Israel/NASEN 2009 survey (adjusted for assumed 10% uncounted)
vi # new syringes from SEPs per IDU per yr
29.9
vii # new syringes from other sources per IDU per yr
157.7
parameter value sources/basis
viiiSEP syringe coverage /base case
2.9% of injs
ixSEP cost per syringe /typical
$0.72average of 2005-2009 SEP unit costs (Beth Israel/NASEN survey), converted to 2011 dollars
xSEP cost per syringe /minimal
$0.36assumed to be half of typical cost (Des Jarlais expert opinion)
xirate at which SEP syringes replace non-SEP syringes
10%no data, assumed to be 10%, i.e.
xiinumber of HIV infections due to drug injection risk in the US per year
2575based on HIV incidence estimates for 2009 (CDC); assuming 1/2 IDU + 1/4 MSM/IDU categories due to injection risk (Des Jarlais expert opinion)
xiiiper case HIV lifetime treatment cost
$388kaverage lifetime treatment cost for an HIV infected person for 2010 (CDC) converted to 2011 dollars
Minimum number of infections averted in a yearif SEP syringe coverage is raised from current level of 2.9% of injections to:
Cost per additional infection averted:
from $111k (SEP 5%)to $129k (SEP 10%) based on โtypicalโ SEP service cost ($0.72 per syringe)orfrom $55.5k (SEP 5%)to $64.5 (SEP 10%)based on โminimalโ service cost ($0.36 per syringe)
Return on investment:from 3.5 (SEP 5%)to 3 (SEP 10%)
Additional investment required per year& savings in HIV treatment costs (million 2011 USD)
for each SEP syringe coverage level
TYPICAL SERVICE
MINIMAL SERVICE
Additional investment required per year& savings in HIV treatment costs (million 2011 USD)
for each SEP syringe coverage level
Return on investment:from 7 (SEP 5%)to 6 (SEP 10%)
Sensitivity analysis
ParameterMain
analysis value
Lower Higher
1 number of injections per IDU per day 2.8 2.5 3.1
2 borrowing probability 0.083 0.07 0.10
3 proportion SEP syringes uncounted 10% 5% 15%
4number of times an IDU uses one own-syringe
5 4 7
5 proportion of infections due to injecting risk
in IDU category 50% 35% 65%
in MSM/IDU category 25% 20% 30%
6 replacement effect 10% 5% 15%
7 number of full-year equivalent IDUs 1.23m 1.0m 1.5m
Sensitivity analyses
Minimum Rate of Return on Investmentโ dollars saved per dollar invested โ
2.8 2.7 2.6 2.5
2.9 3.0 3.1
based on MINIMAL service cost
based on TYPICAL service cost
BREAK-EVEN LINE
Minimum Rate of Return on Investmentโ dollars saved per dollar invested โ
Minimum Rate of Return on Investmentโ dollars saved per dollar invested โ
Key results (main):
If increase SEP syringe coverage from current 2.9% of injections to5% โ 10%
ร Avert about 170 โ 500 HIV infections per year
ร Require 19 โ 64 million USD additional funding (for typical SEP services)or 9.4 โ 32 million USD (for minimal exchange service)
ร Save 66 โ 193 million USD in HIV treatment cost
ร Rate of return on investment 3.5 โ 3 (or 7 โ 6)
Conclusion:
It would be highly cost-saving to increase investment in syringe exchange in the US.
Recommendation:
Syringe exchange should be made a priority in HIV prevention in the US.
The ban on use of federal funding for syringe exchange should be lifted, and federal funding should be allocated to syringe exchange.
THANK YOU!