LINTHICUM, MD, June 22 - Needle-exchange programs that would provide addicts with syringes that are hard to reuse will find HIV rates not dropping but increasing, according to an article in this month's special edition of a journal published by the Institute for Operations Research and the Management Sciences (INFORMS).
"You'd think that distributing syringes that can't easily be infected or passed among addicts would cut the spread of AIDS," says Dr. Edward H. Kaplan, a management scientist at the Yale School of Management and an author of the article. "But sometimes, what seems like a good idea just isn't."
"In this case, introducing the new syringes into the current needle population could change HIV risks, and not necessarily for the better," says Dr. Jonathan Caulkins of RAND and Carnegie Mellon University, the study's lead author and an authority on drug policy.
The study appears in a special issue about AIDS in Interfaces: An International Journal of the Institute for Operations Research and the Management Sciences. Dr. Kaplan, the author of a seminal study supporting needle exchange programs, will speak on AIDS and Israel's blood supply at the 12th World AIDS Conference in Geneva from June 28 to July 3. A number of contributors to the special issue will offer papers and oral presentations at the convention.
Plausible But Wrong
With at least half of new HIV infections in the U.S. occurring among addicts who take drugs intravenously, methods for preventing HIV transmission via needle reuse have received considerable attention. One proposal is engineering and distributing syringes that are not easily shared. Currently, there are several different possible designs of difficult-to-reuse syringes, also known as DTRs.
Mathematical modeling, the key tool employed by management scientists and operations researchers, shows that DTRs would make the AIDS epidemic worse. The study examines one proposal, the introduction of DTRs via a one-for-one exchange for regular syringes. In that case, while both DTR and regular syringes would be present in the population of drug users, the total number of needles used over time would remain the same.
The authors' examination shows why this approach to reducing AIDS is flawed. In such a circumstance, there will be two types of needles with two levels of risk. The number of injections per DTR would be lower than the pre-intervention average number of injections per syringe. Consequently, the fraction of DTRs that are both infectious and available for reuse will be lower than the fraction of needles that were infected prior to the intervention.
Unfortunately, the number of injections per regular syringe will increase from pre-intervention levels; this will increase the fraction of regular syringes that are infectious and available for reuse. Furthermore, the fraction of all injections that would occur with these riskier needles would exceed the fraction of all needles that are easy to reuse. Therefore, the authors conclude, the overall risk of exposure to an infectious needle would actually increase.
Alternate Solution Also Flawed
Alternately, say the authors, DTRs could be distributed rather than exchanged on a one-for-one basis for regular syringes. In that case, simply introducing additional DTRs to the population of all needles would indeed reduce the fraction of circulating needles that are infectious. Surprisingly, though, introducing the same number of regular syringes would reduce the risk from infectious needles by an even greater amount.
To prove useful, say the authors, the number of DTRs introduced must be large relative to any reduction in the consumption of regular needles. For the number of potentially infectious needles to remain the same, any reduction in regular needles must be met by an increase in the rate of DTRs that is at least 40% larger.
There are additional problems. DTRs are more expensive than regular needles. That expense would be compounded if 40% more DTRs than regular needles are used. Ease of use is also an issue: Some focus groups of drug users have reported that DTRs interfere with the injection process and are less desirable than regular needles.
As a result, the authors recommend against difficult-to-reuse syringes, arguing that regular needles are always superior in reducing the risk of HIV transmission among addicts who take drugs intravenously.
The study, "Can Difficult-to-Reuse Syringes Reduce the Spread of HIV Among Injection Drug Users?" was written by Jonathan P. Caulkins of Carnegie Mellon University and RAND; Edward H. Kaplan of the Yale School of Management; Peter Lurie of the Center for AIDS Prevention Studies; Thomas O'Connor; and Sung-Ho Ahn of RAND. It appears in a special issue about AIDS in Interfaces: An International Journal of the Institute for Operations Research and the Management Sciences.
The Institute for Operations Research and the Management Sciences (INFORMS) is an international scientific society with 12,000 members, including Nobel Prize laureates, dedicated to applying scientific methods to help improve decision-making, management, and operations. Members of INFORMS work primarily in business, government, and academia. They are represented in fields as diverse as airlines, health care, law enforcement, the military, the stock market, and telecommunications.
Journal
Interfaces