An Evaluation of Needle and Syringe Exchange in San Francisco

Publication Details

John K. Watters

Urban Health Study, Institute for Health Policy Studies, and Department of Family and Community Medicine, School of Medicine, University of California, San Francisco;

Michelle J. Estilo

College of Physicians and Surgeons, Columbia University;

George L. Clark

Prevention Point Research Group, San Francisco, California; and

Jennifer Lorvick

Urban Health Study, Institute for Health Policy Studies, School of Medicine, University of California, San Francisco

Introduction

The sharing of contaminated injection paraphernalia is a major route for transmission of human immunodeficiency virus (HIV) in the United States (1, 2, 3) and is one of the principal means by which HIV infection has spread in Italy, Spain, and Thailand (1, 4). In the U.S., one quarter (24%) of the 310,780 AIDS cases diagnosed among adults and adolescents through June, 1993 occurred among heterosexual injection drug users (IDUs). An additional 3.5% (10,800) were adults whose sole risk factor was having a sexual partner who injected drugs. Over half (56.2%) of the pediatric AIDS cases diagnosed in the U.S. through June, 1993, were attributed to HIV transmission from mothers who injected drugs themselves or who engaged in sexual activity with injection drug users (5 ). It is estimated that there are 1.2 million IDUs in the United States, about 15% of whom are believed to be enrolled in drug treatment on any day (6 ). Successful prevention of further spread of HIV in this population is crucial to national infectious disease prevention objectives (7 ). An unknown number of Americans in these risk categories are infected with HIV.

In an effort to reduce the sharing of injection equipment, programs have been established which provide sterile needles and syringes to drug users in exchange for their used equipment. Previous studies have reported that syringe exchange programs have played a significant role in lowering rates of needle-sharing in Amsterdam, (8, 9); Sweden (10 ); Australia (11 ); the United Kingdom (12, 13, 14); Tacoma, Washington (15 ); New Haven, CT (16 ); and New York City (17, 18). Other studies have reported that syringe exchange programs have served as sources of referrals into social services, medical services and drug treatment (16, 19). In New Haven, researchers reported that new HIV infections among clients of a legal syringe exchange had been reduced by one-third (17 ).

Opponents of syringe exchange have claimed that these programs will facilitate and therefore increase illicit drug injection. We conducted a study to determine whether syringe exchange is harmful or beneficial as risk reduction for injection drug users. We evaluated an all-volunteer syringe exchange program in San Francisco, CA known as ''Prevention Point." Estimates of the number of injection drug users in San Francisco, range from 13,000 to 16,000 in a city of approximately 740,000. The daily census in drug abuse treatment programs in San Francisco is approximately 1,500 individuals. Waiting lists for publicly supported drug treatment slots exist in virtually all clinics.

Three research questions relevant to the health policy debate regarding syringe exchange were used as evaluation criteria: (1) how readily and to what degree has the syringe exchange been used by IDUs; (2) to what degree has syringe exchange stimulated injection drug use through increased injection frequency and recruitment of new users; and (3) to what degree is the use of syringe exchange predictive of abstinence from syringe sharing?

Methods

Data Sources and Sampling

Data for the study were derived from two sources: (1) the Urban Health Study, a semi-annual survey of IDUs in San Francisco; and (2) Prevention Point syringe exchange program records. The Urban Health Study is a semi-annual cross-sectional study of IDUs recruited in natural settings in three inner-city communities in San Francisco. During the 1987 through 1989 cross-sections, respondents were also sampled in two 21-day drug detoxification clinics. Communities chosen for study were selected for high densities of IDUs relative to other San Francisco neighborhoods as indicated by review of drug treatment program admissions, drug arrest data, and ethnographic studies. All respondents were screened for visible signs of repeated drug injection. After the purpose of the study was explained, and informed consent obtained, respondents were interviewed using a standard questionnaire dealing with AIDS knowledge; medical, drug use, and sexual histories; and known HIV/AIDS risk behaviors. Interviews were conducted by trained interviewers employed by the Urban Health Study. Respondents were paid for their participation, given pretest and posttest counseling, and given referrals to medical and social services by trained staff. In the present study, we used eleven semi-annual cross-sectional surveys collected as part of the Urban Health Study, between January 1987 and June 1992 (n = 6216). Excluded from further analysis were 572 respondents who reported no current injection drug use. The number of interviews included for each of the cross-sections were as follows: Spring 1987, n = 596; Fall 1987, n = 576; Spring 1988, n = 598; Fall 1988, n = 607; Spring 1989, n = 505; Fall 1989, n = 503; Spring 1990, n = 411; Fall 1990, n = 460; Spring 1991, n = 456; Fall 1991, n = 459; Spring 1992, n = 473.

"Prevention Point" is a volunteer-based syringe exchange program which began operating in November 1988 on a San Francisco street corner, and in a second neighborhood using a "mobile" team. The mobile team used a baby perambulator to deliver necessary supplies to a neighborhood that contained many homeless persons. Additional street corner sites were added in May, 1989; September, 1990; and December, 1991. In September, 1992, the original mobile team was reassigned to two different fixed locations. During the study period, all exchange sites operated during evening hours (6:00 to 8:00 pm). While technically illegal, the Prevention Point program has operated without major disruption from police and with the tacit approval of two successive mayoral administrations. Program volunteers provide a strict one-for-one exchange in which a sterile, single-use, 27.5-gauge, 0.5 inch, 1 cc, U-100 insulin syringe is exchanged for each syringe deposited in a Sharps biohazardous waste container by the client. Limitations on the number of syringes program clients were permitted to exchange have changed over the course of the study. Prior to May, 1989 a ten syringes per client visit limit was in effect. Between May 1989 and August 1990, this limit was increased to twenty syringes per client visit. In August, 1990 all limits on the number of syringes that could be exchanged were abandoned. Volunteers also distribute one-ounce bottles of bleach, condoms, cotton, and alcohol wipes, and provide referrals to drug treatment, HIV testing and counseling and other social and medical services upon request. Prevention Point records used for this study extend from program implementation (November, 1988) through mid-1992. Client contacts were recorded on a standard form by program personnel each time an individual presented at a Prevention Point site and exchanged at least one syringe.

Outcome Measures

Utilization of syringe exchange program was assessed using three indicators: (1) the number of client contacts and syringes exchanged as reported in program records of Prevention Point syringe exchange program; (2) frequency of visits to syringe exchange as reported by participants in the Urban Health Study from 1989 to 1992; and (3) sources of syringes reported by Urban Health Study participants interviewed between 1987 and 1992. Negative impacts of the syringe exchange program were examined using three variables included in the Urban Health Study dataset: (1) changes in the self-reported frequency of injection over time (1987-1992); (2) changes in the age distribution of the cross-sections (1987-1992); and (3) proportion of respondents reporting first injection during previous year (19891 to 1992). Syringe-sharing was examined by assessing the relationship between reported syringe exchange use in the past year and reported needle-sharing based on self-reported number of needle-sharing partners in the 30 days prior to interview. The accuracy of the term "needle-sharing" has been questioned, since IDUs may use previously-used syringes that are not perceived as "shared" (20 ). Consequently, participants in the Spring 1992 cross-section (N = 473), were asked if they injected during the past 30 days using syringes that they know had been used by someone else, including a close friend or lover. The Pearson product moment correlation coefficient between this variable and reported "needle-sharing" in the past 30 days was robust (r = 0.83, p < 0.01).

Correlates of needle-sharing were identified using a pool of 752 unduplicated respondents from the most recent full year of data available (Fall 1991/Spring 1992). In instances of multiple interviews, only the first observation was used. Out of 932 interviews, 176 "duplicate" observations and 4 observations with missing data concerning syringe-sharing behaviors were dropped from this analysis. The demographic composition of this cross-section closely approximated the entire sample (data not shown).

Statistical Analysis

One-way analysis of variance with Scheffe's test for multiple comparisons was used to identify differences in the mean number of syringes exchanged and the reported frequency of injection over successive cross-sections. Differences in the proportion of IDUs utilizing the syringe exchange >25 times in the past year, and the proportion of new injectors over-time were assessed using the Mantel-Haenszel χ 2 test for trend. Differences in odds ratios between cross-sections were tested using Woolfs method, and summary odds ratios were calculated when appropriate (21 ). For univariate comparisons, two-tailed χ 2 tests or Fisher's exact tests were used to examine the relationship between categorical variables and needle-sharing in the past 30 days; Student's t-tests were used to examine the relationship of continuous variables. Odds ratios and 95% confidence intervals were computed for categorical variables. Multiple linear regression (for continuous outcomes) and logistic regression (for categorical outcomes) was used to control for possible cohort effects in comparisons made over multiple cross-sections. Factors predicting needle-sharing were identified using nonhierarchical logistic regression in a Fall 1991/Spring 1992 sub-sample (n = 752). All possible interactions of main effects were tested. Statistical analysis was performed using the Statistical Package for the Social Sciences, Chicago, Illinois (22 ).

Results

Table 1 presents selected demographic characteristics of the study population. Analyses of cross-sections were performed over the eleven cross-sections of data incorporated in the study. Changes in grant support forced the elimination of the 21-day drug detoxification clinics from the sampling frame in January, 1990. This resulted in two post-January 1990 changes in sample composition: (1) the proportion of IDUs enrolled in drug treatment programs decreased from 37% to 17%; and (2) the percentage of African Americans increased from 47% to 56%, the percentage of Hispanics decreased from 17% to 14%, and the percentage of Caucasians decreased from 36% to 30%. Among street-recruited IDUs, there was no significant change in proportion of respondents enrolled in drug treatment over the 11 study cross-sections. Changes in sampling frame occurred prior to the 1991-1992 cross-section used in our analysis of needle-sharing in Table 2 and Table 3.

Table 1. Selected Demographic Characteristics: IDUs in San Francisco, 1987-1992 (N=5,644).

Table 1

Selected Demographic Characteristics: IDUs in San Francisco, 1987-1992 (N=5,644).

Table 2. Selected Characteristics and Reported Needle-Sharing in Past 30 Days-Fall 1991/Spring 1992 (N=752).

Table 2

Selected Characteristics and Reported Needle-Sharing in Past 30 Days-Fall 1991/Spring 1992 (N=752).

Table 3. Logistic Regression Analysis of Needle Sharing in Past 30 Days-Fall 1991/Spring 1992 (N=752).

Table 3

Logistic Regression Analysis of Needle Sharing in Past 30 Days-Fall 1991/Spring 1992 (N=752).

Utilization of Syringe Exchange Program

Client contacts reported by Prevention Point rose steadily from program implementation in late Fall 1988 through Spring 1992, when client contacts peaked at 16,600 contacts over a six month period. During Spring 1989, 7,821 syringes were exchanged as compared with 343,883 syringes exchanged during Spring 1992. The ratio of syringes exchanged to clients who presented at the exchange sites increased from two syringes per client contact to 21 syringes per client contact between Fall 1988 and Spring 1992. There was a significant increase in the mean number of syringes exchanged for other people on the part of Urban Health Study respondents between Fall 1989 and Spring 1992 (F = 6.603; p < 0.0001). In Fall 1989, 50 respondents (9.9%) reported exchanging syringes for a mean of 4.3 others, while in the Spring 1992 cross section, 72 respondents (15.2%) reported exchanging syringes for a mean of 10.3 others. Between Fall 19892 and Spring 1992, reported utilization of syringe exchange at any time in the past year by respondents in the Urban Health Study increased from 50% to 61%. The proportion of respondents who reported using the syringe exchange at least 25 times in the past year doubled between 1989 and 1992, from 14% to 28% (Mantel Haenszel χ 2 test for trend = 40.26; df = 1; p < 0.00001).

We also found major shifts in the principal sources of syringes reported by Urban Health Study respondents between 1987 and 1992. An increase was observed in the proportion of respondents who reported syringe exchange as their usual source. By Fall 1990, syringe exchange had become the most frequently cited source of syringes and remained the major source of syringes throughout the observation period. In Spring 1992, 45% of respondents interviewed reported "usually" obtaining their injection equipment by exchanging at Prevention Point. Thirty-two percent reported that buying syringes on the street was their usual source, while 23% reported using other sources including friends, relatives, diabetics, pharmacies, dealers, shooting galleries, renting or stealing syringes see (see Figure 1).

Figure 1. ''How do you usually obtain syringes?" San Francisco drug injectors, 1987 a-Syringe exchange begins Nov.

Figure 1

''How do you usually obtain syringes?" San Francisco drug injectors, 1987 a-Syringe exchange begins Nov. 1988/10 syringe limit. b-May 1989/20 syringe limit. c-August 1990/syringe limit is abandoned.

Frequency of Injection

The median number of reported daily injections in the year prior to interview declined between 1987 and 1992 from a high of 1.9 per day in Fall 1987 to 0.7 in Spring 1992. Median daily injection frequencies in the past year peaked prior to implementation of syringe exchange. This decline in injection frequency over time was significant in analysis of variance over the eleven cross-sections (F = 16.17; p < 0.0001). Scheffe's test for multiple comparisons revealed a significant decline (p < 0.05) between the Spring 1987 to Fall 1988 cross-sections, and between the Fall 1990 and Spring 1992 cross-sections.

Recruitment of New and Younger Users into Injection Drug Use

Over the five and one-half year study period, the mean age rose six years, from 35.8 years in Spring 1987 to 41.6 years in Spring 1992. Age was normally distributed, and the mean standard deviation for the eleven cross-sections was 8.3 years. Minimum age did not change significantly between cross-sections. The mean age of the youngest participant across samples was 19; minimum age ranged from 15 to 20. We found a significant progressive decline in the proportion of persons who reported first injecting drugs in the previous year, from 3.0% in Spring 19893 to 1.1% in Spring 1992 (Mantel-Haenszel χ 2 test for trend = 9.65; df = 1; p < 0.002).

Syringe Sharing-Univariate Analysis

An overall decline in sharing behavior was observed throughout the observation period with 66.3% reporting sharing in Spring 1987 and 35.5% reporting sharing in Spring 1992. We found no remarkable differences in the proportion of non-users of the exchange who reported sharing needles over the three-year observation period (1989-1992) following program implementation. When all observations from 1989-1992 were considered, IDUs who reported syringe exchange use > 25 times in the past year were less likely to report needle-sharing in the past 30 days than those who used the exchange less frequently or not at all (Mantel-Haenszel summary odds ratio = 0.71; 95% confidence interval = 0.59, 0.87).

The unduplicated Fall 1991/Spring 1992 sample (n = 752) closely approximated the demographic composition of the total sample. Univariate relationships to needle-sharing in the past 30 days from variables in the Urban Health Study data-set may be found in Table 2. A smaller proportion of African-Americans reported needle-sharing in the past 30 days. Homelessness, reported injection of "speedballs" (concurrent injection of heroin and cocaine), heroin injected alone, injected-cocaine, and crack cocaine use in the past month, had significant associations with needle-sharing. Daily injection drug use ( ≥ 30 injections in past 30 days) and a history of drug treatment within the past five years were also associated with needle-sharing. Both older age and needle-exchange as primary syringe source had protective effects. Respondents who reported regular use of bleach within the past six months were less likely to share syringes, as were respondents who reported use of condoms 100% of the time during sexual activity.

Syringe Sharing-Multivariate Analysis

In logistic regression, we found six main effects independently associated with needle-sharing in the past 30 days (see Table 3). Greater frequency of syringe exchange use in the past year was associated with not sharing syringes in the past 30 days. Other protective factors associated with sharing syringes were: increasing age, African American ethnicity, reported condom use 100% of the time during penetrative intercourse (anal, oral, vaginal); and having previously received a HIV antibody test result. Frequency of injection of cocaine in the previous month was a significant predictor of needle-sharing. We found a significant interaction between two continuous variables in the logistic regression model which improved the fit of our model to the data. This interaction adjusts for the difference in the effect of syringe exchange use on sharing behavior relative to years of age. The relationship between needle-sharing, age, and frequency of syringe exchange use is illustrated in Figure 2. Curves depict adjusted odds ratios for needle-sharing for selected age groups. The median age (40 years) for the Fall 1991/Spring 1992 subsample (n = 752) was selected as the referent for calculating odds ratios to illustrate the interaction. Figure 2 shows a decline in the likelihood of needle-sharing among 20 and 30-year olds with increasing frequency of syringe exchange use when adjusted for factors in the model. There was no change in needle-sharing likelihood among 40 and 50 year olds with increasing use of syringe exchange.

Figure 2

Figure 2

Adjusted odds of needle sharing (30 days) by age and frequency of syringe exchange us previous year

Discussion

Our findings confirm that IDUs will participate in syringe and needle exchange programs that can be easily approached and negotiated. In San Francisco, syringe exchange was readily adopted by IDUs, and appears to have quickly replaced the black market as a primary source of injection equipment. The ability of syringe exchange to recapture used and potentially infectious syringes for safe disposal should also not be underestimated. During October, 1992, the Prevention Point syringe exchange program collected and safely incinerated approximately 13,000 used syringes each week. In a recent study, investigators detected HIV-1 antibodies in 7% of a random sample of 83 syringes returned to the San Francisco syringe exchange program (23 ). By extrapolation, approximately 3,600 syringes contaminated with HIV were removed from the environment during the month of October, 1992 by the syringe exchange program. There was no support for the hypothesis that syringe and needle exchange contributes to drug abuse in our study population. The gradual but statistically significant decline in self-reported frequency of injection over the study period may reflect a historical artifact which mirrors growth in the popularity of "crack" cocaine (which is smoked, not injected), or other unmeasured factors. We found a decreasing level of initiation into drug injection over-time. Guydish et al. (24 ) noted similar declines in needle-sharing and initiation into injection drug use among persons admitted to drug-abuse treatment programs in San Francisco before and after implementation of the syringe exchange program. Fluctuations in drug use practices are common (25 ), and initiation into drug use (including the practice of injection) have been shown to be influenced by the interplay of a host of familial, social, psychological, cultural, and historical factors (26, 27, 28, 29, 30, 31). Previous studies reported needle-sharing was lowered among non-exchangers as well as regular exchangers in the Netherlands and the United Kingdom (32, 33). However, in our study, we found no significant decline in needle-sharing over-time among respondents who reported no syringe exchange use in the year prior to interview. These differences in study outcomes may stem from different drug use patterns, exchange program structures, and/or social circumstances found among European IDUs and those studied in San Francisco.

We found syringe exchange use to be a strong, independent predictor of not sharing needles and syringes in the recent past when adjusted for age, ethnicity, previous HIV testing and counseling, frequency of injection of cocaine, and consistent use of condoms. Younger IDUs were more likely to report needle-sharing than their older counterparts overall, but were less likely to report needle-sharing with more frequent use of syringe exchange. This finding is reflected in the interaction of age and frequency of syringe exchange use in multivariate analysis. Thus, the San Francisco syringe exchange program appears to have had its greatest benefit among younger users. We speculate these younger persons depend more heavily upon syringe exchange as a source of clean injection equipment than do older IDUs with other established sources for needles and syringes.

Other factors with independent relationships to needle-sharing were race, condom use, and injection of cocaine. It is noteworthy that African American ethnicity was inversely related to syringe sharing. Other studies have found African American IDUs to be at elevated risk for HIV infection relative to IDUs who are members of other ethnic groups in San Francisco (34, 35) and elsewhere (36, 37). African American ethnicity has been found as an independent risk factor for HIV in multivariate models that include injection frequency (35, 38). Possible reasons for this include differential reporting bias and/or social factors related to social networks, sexual activity, and sharing practices that are neither well measured nor understood. IDUs who reported consistent use of condoms "all of the time" were less likely to share syringes. We have previously reported that changes in sexual behavior in response to AIDS prevention messages have trailed gains in needle-cleaning and not sharing (39 ). It is possible that those who are able to negotiate the use of condoms in the intensely personal and subjective domain of human sexual behavior, are likewise better able to adapt their behavior to avoid needle-sharing. Recent injection of cocaine predicted needle-sharing in multivariate analysis. This may reflect the subordination of health concerns to the drive to inject drugs with whatever equipment is available. Cocaine injectors, who typically inject many times during a "run" of one or several days, may have difficulty obtaining a sufficient supply of clean needles. We speculate that prevention programs, including syringe exchange efforts, will need to reach into the environments where these individuals practice high-risk behavior in order to adequately support the adoption of lower risk alternatives to needle-sharing. We think it especially noteworthy that having received a previous HIV test result (which by California law are voluntary, confidential, and include both pre-test and post-test counseling), was a significant, independent predictor of not-sharing needles. This effect was independent of the outcome of the HIV antibody test (positive or negative). Our study is limited in that it identifies correlates of sharing syringes but not causes of reduced sharing. As is the case with virtually all survey research, we used self-reports of respondents recruited into the study from the population of interest; in this case IDUs. Consequently, these data may be subject to problems of recall, intoxication, socially desirable responses, and/or other sources of bias (40 ). However, high validity of self-reported drug use in a multi-site study using similar methods and instrumentation has been reported (41 ). The targeted samples used were not true random samples, therefore our findings may not generalize to other populations of IDUs. The short (30-day) timeframe used for some items is a limitation. However, the use of longer periods may amplify problems in accuracy of recall. Despite these limitations, the study contains useful information regarding a significant health technology and related policy issue: namely, the feasibility, and potential risks and benefits of syringe exchange as a method of HIV/AIDS prevention for IDUs.

In multivariate analysis, two inverse correlates of syringe-sharing appeared as promising health interventions. These were syringe exchange and voluntary, confidential HIV testing and counseling. While an independent factor associated with not sharing needles, syringe exchange should not be viewed as a substitute for a comprehensive approach to drug abuse treatment and prevention, nor as an infectious disease prevention nostrum. However, our findings are consistent with other studies that have suggested that increased availability of sterile syringes can play a useful and significant role in helping to attenuate the practice of needle-sharing, and the high rate of infectious disease transmission that accompanies this practice (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 42). Our results suggest that syringe exchange programs and voluntary HIV testing and counseling help reduce needle-sharing. Such programs should be continued, expanded to meet existing needs, and implemented in areas where not currently available.

Acknowledgments

A previous version of this paper was read at the VII International Conference on AIDS, Florence Italy, June, 1991. The authors are especially grateful for the support of the American Foundation for AIDS Research (Grant number 001037-7RG). Additional support for this study was derived from the San Francisco Department of Public Health, Office of AIDS (contract # 83-07069); the U.S. Centers for Disease Control (cooperative agreement # U62-CCU902017); and the National Institute on Drug Abuse (grant nos. RO1 DA04212 and UO1-DA06908). Acknowledged are the contributions of the study participants; and the staff of the following organizations: Prevention Point Needle Exchange Program; Haight-Ashbury Free Clinics, Inc.; San Francisco General Hospital Substance Abuse Services; the Mid City Consortium to Combat AIDS; and the Urban Health Study, School of Medicine, University of California, San Francisco. Acknowledged also are the contributions of Yu-Teh Cheng, M.A., Kyung Hee Choi, Ph.D., M.P.H., Brian Edlin, M.D., T. Stephen Jones, M.D., Walter Hauck, Ph.D., Alex Kral, M.S., Mark Segal, Ph.D., Starley B. Shade, B.A., and David Vlahov, Ph.D.

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Footnotes

1

Item added to survey questionnaire in Spring 1989.

2

Needle-exchange item first added in Fall 1989 survey.

3

Age of first injection was introduced in the Spring 1989 questionnaire.