Injecting drug users (IDU) and crack users remain at high-risk for HIV in the United States, especially on the East Coast [1
]. A recent study estimated that there are over 1.8 million IDU in the US, of whom 16% are HIV+ [2
]. Nearly a quarter of currently prevalent HIV cases are attributable to injection drug use or both IDU and male-to-male sexual contact [3
]. Concurrently, there are 1.5 million crack users [4
], each having a threefold risk of acquiring HIV [5
]. Among drug users, HIV risk emerges not only from drug use (i.e., by sharing needles), but also from sexual behaviors [6
]. Therefore, it is critical to design and evaluate evidence-based interventions for IDU and crack users. This article re-evaluates the efficacy of Safety Counts, an intervention to reduce both drug and sexual risk among serious drug users.
Needle exchange and methadone maintenance are two effective strategies for reducing HIV risk for IDU [7
]. However, despite multiple scientific reviews on its efficacy, most communities in the US do not have access to needle exchange and there are many parts of the world without such access. Given the political realities of acceptable treatments, this study examines an intervention strategy built concurrently with the street-outreach models of the AIDS Community Demonstration Projects [8
Drug use is concentrated within specific neighborhoods [1
], leading consequent HIV risk to be closely linked to geography [9
]. Within neighborhoods with high drug use, there are local “hang-out” sites that are frequented by drug users (shooting galleries, squats). Coincident with drug use and HIV risk, drug-infested neighborhoods have high rates of sexually transmitted diseases and crimes. Because of this geographic concentration, street outreach prevention strategies are desirable [10
]. By intervening in neighborhoods with high rates of drug use, it is easier and more efficient to target prevention resources, maximizing the cost-effectiveness of prevention funding. Simultaneously, there are likely to be spill-over benefits from interventions that concentrate on neighborhoods: peers and social networks exert a strong influence on individuals’ high-risk behaviors [12
Street outreach workers can contact drug users in their local hang-outs to deliver HIV prevention messages, both about reducing drug use and increasing condom use. Outreach workers can also facilitate the engagement of drug users into ongoing group and community activities, increasing the exposure to prevention messages, increasing the practice of new behaviors, and building positive social networks. Street-based recruitment and prevention strategies address both the physical and the social dimensions of drug abuse [10
] and require that evaluations be based upon interventions delivered at the level of the site, even if tailored to the individual [15
This study implemented a prevention program for street-based drug users, called Safety Counts. Drug users do not usually access health services or seek care at institutions such as schools, churches, or community centers [13
]. Therefore, Safety Counts built on a street outreach approach. The intervention was based on several related theories of behavior change, with the Transtheoretical Stages of Change Model of Prochaska and DiClemente [17
] forming the core framework. The intervention also drew on behavior change principles and techniques articulated by social cognitive theories [19
]. Further information about the Safety Counts intervention can be found in the Program Implementation Manual [22
] and an earlier article by Rhodes and Humfleet [23
Following the protocol of the National Institute on Drug Abuse (NIDA) Cooperative Agreement, this study used the NIDA Standard Intervention for drug users [24
] as the control condition. Labeled as VCT in this paper, the control condition delivered a didactic voluntary counseling and testing program over two sessions, in order to inform individuals regarding their HIV serostatus and to motivate them to reduce existing sexual risk acts. The enhanced intervention, Safety Counts, included the VCT sessions plus street outreach, skills-building workshops, individual counseling, and social events. Based on these components and the social cognitive theoretical models common to evidence-based interventions [25
], the 7-session Safety Counts Program was delivered to neighborhood drug users. Both self-report and urine screens for active drug use were utilized as outcome measures for the intervention.
Hershberger and colleagues evaluated the Safety Counts intervention in this journal in 2003, finding few significant outcomes of the Safety Counts intervention compared to the standard VCT condition. Our analyses adopt a different perspective towards the data. The prior analyses emphasized as-treated comparisons of compliers in each condition (although intent-to-treat results were presented in the text as well). Those who did not complete the full intervention schedule were discarded from the primary analyses. A key difference between that paper and the present one is our emphasis on intent-to-treat comparisons of those assigned to the VCT control condition and those assigned to Safety Counts.
Beyond the difference in emphasis, the determination of which potential participants to include in the intent-to-treat analyses was not the same in the two studies. In the present study, completion of the NIDA Standard Intervention (attending two sessions) was a criterion for eligibility, and we excluded individuals who did not complete both sessions. In addition, we excluded from analysis those who reported lengthy incarcerations at either the baseline or follow-up assessment, as that reduces the individual’s behavioral autonomy. The Hershberger et al. analyses did not make these exclusions.
Another difference between the two studies is that we analyzed the data using some additional outcome markers. The authors of the prior paper analyzing Safety Counts chose several dichotomous outcome measures such as any sexual activity or not, any unprotected sex or not, multiple partners or not, using crack or not, and any injection drug use or not. They also measured selected risky behaviors as percentages: percent of times injected with dirty works, percent of times used condoms. We analyzed a subset of the dichotomous outcome measures from the prior study, with some modifications to definition or analytic method.
However, in addition to these measures, we also used count measures of how frequently the behaviors were practiced, such as number of times injecting (also used in the prior study), number of times using dirty works, number of times using crack, number of times having sex, and number of unprotected sexual risk acts. We did not use outcomes expressed as percentages. We believe that counts provide a useful measure of absolute risk that is superior to percentages. In the case of condoms, for example, count measures capture frequency of sexual activity, as well as relative frequency of condom use. A person using condoms 30 times out of 60 is at greater risk than a person using condoms two times out of four, yet a dichotomous indicator of practicing unsafe sex, or a percentage measure of condom use would not differentiate between these two individuals.
We also chose different methods to analyze the frequency measures. Data plots showed that these measures were not normally distributed, but in fact followed a Poisson distribution. We therefore used random effects models assuming a Poisson distribution for count variables. We believe that this analytic method provides a better fit to the data than did the methods used by the authors of the prior published analyses. For frequency measures, they used a two-way ANOVA approach, which assumes that variables follow a normal distribution. This was not the case for the count (times injected) or percentage variables examined in that study. We feel that the choice of appropriate sample and outcome measures in conjunction with correct statistical methods will provide a more accurate evaluation of the actual intervention impact.