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Determinants of Cutaneous Injection-Related Infection Care at a Supervised Injecting Facility
Determinants of Cutaneous Injection-Related Infection Care at a Supervised Injecting Facility ELISA LLOYD-SMITH, EVAN WOOD, MD, PHD, RUTH ZHANG, MSC, MARK W. TYNDALL, MD, SCD, JULIO S. MONTANER, MD, FRCPC, AND THOMAS KERR, PHD
PURPOSE: To evaluate the factors associated with receiving cutaneous injection-related infection (CIRI) care among a representative cohort of supervised injecting facility (SIF) users. METHODS: Data were collected biannually as part of a prospective cohort, the Scientific Evaluation of Supervised Injection study. Kaplan-Meier methods and Cox proportional hazards regression with recurrent events were used to examine incidence and factors associated with CIRI care, respectively. RESULTS: One thousand eighty individuals were recruited between December 1, 2003 and January 31, 2008. The incidence density of participants receiving CIRI care was 22.0 per 100 person-years (95% confidence interval [CI]: 19.6–24.6). In the adjusted Cox proportional hazard model, female sex (adjusted hazard ratio [AHR] Z 1.87 [95% CI: 1.32–2.64]), unstable housing (AHR Z 1.39 [95% CI: 1.02–1.88]), and daily heroin injection (AHR Z 1.52 [95% CI: 1.13–2.04]) were independently associated with receiving CIRI care at the SIF. CONCLUSIONS: These results describe who is more likely to receive CIRI care, which is of use to those engaged with policy and practice of treatment regimens involving this population. Ann Epidemiol 2009;19:404–409. Ó 2009 Elsevier Inc. All rights reserved. KEY WORDS:
Statistical Methods, Infectious Disease, Nursing, IV Drug User.
INTRODUCTION Cutaneous injection–related infections (CIRI), which includes abscesses and cellulitis, are prevalent among persons who inject drugs (IDU) (1, 2). Although these infections are known to constitute a primary cause of morbidity among IDU (2, 3), there is a paucity of research in this area (4). Most of the literature on the treatment of CIRI has been derived from hospital- and emergency department (ED)–based chart reviews, and most has been carried out in the United States (5–9). Financially the burden of CIRI in the medical system is substantial. A general hospital in San Francisco reported a conservative estimate of ED costs in excess of $20 million per year (10). Several models of care have been shown to effectively incorporate both CIRI treatment and wound care and to result in cost savings (8, 11, 12). In San Francisco, the Integrated Soft Tissue Infection Services (ISIS) clinic has been
British Columbia Centre for Excellence in HIV/AIDS (E.L.S., E.W., R.Z., M.W.T., J.S.M.), School of Population and Public Health (E.L.S., M.W.T.), Department of Medicine (E.W., J.S.M, T.K.), University of British Columbia, Vancouver, Canada. Address correspondence to: Thomas Kerr, BC Centre for Excellence in HIV/AIDS, St. Paul’s Hospital 608-1081 Burrard St, Vancouver, BC V6Z 1Y6, Canada. Tel: (604) 806-9116. fax: (604) 806-9044. E-mail: uhri@ cfenet.ubc.ca. Received September 8, 2008; accepted March 2, 2009. Ó 2009 Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010
found to be a valuable and cost saving program (8). The program has changed a predominantly inpatient model to that of an outpatient model of care that offers surgical interventions, counseling, and social services for individuals with soft tissue infections (8). In the first year of operation, results from the clinic reported a 47% decrease in surgical service hospital admissions, a 34% reduction in ED visits, and an estimated savings of over $8 million (8). Another example of effective treatment for CIRI outside the hospital setting is a wound management clinic that operates in conjunction with a syringe exchange program in New Haven (12). Notably, individuals who access syringe exchange programs that provide primary care services have reported reduced ED utilization (13). Medically supervised safer injection facilities (SIF), where IDU can inject pre-obtained illicit drugs under the supervision of medical staff, operate in several cities in Europe, and in Sydney, Australia (14–16). Within SIFs, individuals are typically provided with sterile injecting equipment and emergency intervention in the event of an accidental overdose, as well as medical care and addiction treatment, either on site or through referral (17, 18). On September 22, 2003, Vancouver, Canada opened North America’s first government sanctioned SIF (14). The objectives of this study were to examine receiving CIRI care as well as factors associated with receiving CIRI care among users of Vancouver’s SIF. 1047-2797/09/$–see front matter doi:10.1016/j.annepidem.2009.03.007
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Selected Abbreviations and Acronyms CIRI Z cutaneous injection-related infection IDU Z injection drug user ED Z emergency department ISIS Z Integrated Soft Tissue Infection Services SIF Z safer injection facilities DTES Z Downtown Eastside IQR Z interquartile range HR Z hazard ratio AHR Z adjusted hazard ratio
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supplies for CIRI, including ‘alleyn’, ‘combiderm’, ‘mesalt’, and ‘iodasorb’. Multiple visits per participant were counted except if a participant had more than one CIRI care episode in one day. In this case, only the first CIRI care event was counted (i.e., one CIRI care episode considered per day). Multiple visits for each participant reflect that CIRI care by nurses often involves numerous visits per infection plus more than one infection per participant during the study period. Statistical Analysis
METHODS Study Sample The Vancouver SIF is being evaluated through the Scientific Evaluation of Supervised Injection study, a prospective cohort that has been described in detail previously (19). The SIF is located in Vancouver’s Downtown Eastside (DTES), which is the epicenter of Vancouver’s IDU population, known as one of the poorest urban postal codes in Canada. The neighborhood is also home to a large open drug and sex work scene and the site of an explosive epidemic of HIV infection. Briefly, since December 2003 participants were recruited during random times from within the SIF. SIF users were eligible to be randomized for selection by the SIF’s intake computer after their second visit. Among individuals who were recruited, an interviewer-administered questionnaire elicited sociodemographic and behavioral information. In addition, participants completed a nurseadministered questionnaire regarding health status and provided venous blood samples for hepatitis C virus and HIV at baseline and at semiannual follow-up visits. Interviewees received CAD$20 for their participation. The SIF intake computer is equipped with a database that tracks utilization of services within the facility (e.g., care by nurse, sessions with addictions counselor) as well as referrals to other services (e.g., hospital or detoxification services) (19). Informed consent was obtained from all participants. The Research Ethics Board at the University of British Columbia approved the present study. Study Outcome The end point in this study was the provision of care at the SIF. Both abscesses and cellulitis were considered to be CIRI. The occurrence of CIRI care events was determined by examining relevant entries by the nurse in the SIF database. Specifically, instances of CIRI care were identified by searching the SIF database for (1) entries describing the provision of care by a nurse for an abscess, a wound, or a skin infection; (2) notes containing ‘abscess’, ‘cellulitis’; or (3) entries describing the provision of nursing care
As an initial step, we examined the total number of CIRI care events at the SIF reported by each participant. We also examined the sociodemographic and behavioral variables, collected as part of the baseline Scientific Evaluation of Supervised Injection questionnaire, stratified by whether receiving CIRI care was or was not obtained at the SIF. Potential explanatory factors considered in subsequent analyses included the following: age, sex (female vs. male), living in unstable housing (yes vs. no), DTES residence (yes vs. no), requiring help injecting (yes vs. no), daily cocaine injection (yes vs. no), daily heroin injection (yes vs. no), and daily speedball injection (yes vs. no). Unstable housing was defined as living in a single room occupancy hotel, shelter, recovery or transition house, jail, on the street, or having no fixed address. Requiring help injecting was based on the question ‘‘Have you needed someone to help you inject?’’ Daily injection of cocaine, heroin, and speedball refers to at least once-daily injection. Behavioral variables referred to self-reported activity in the last 6 months. Variable definitions have been used in previous studies (20, 21). Categorical variables were analyzed using chi-square tests and continuous variables were analyzed by the Wilcoxon rank sum test. The incidence of CIRI care, stratified by sex, was estimated by using Kaplan-Meier methods. Kaplan-Meier curves were compared by the log-rank test. Significant differences (p value ! 0.05) between participants who did and did not receive CIRI care determined variable selection for the unadjusted and adjusted Cox proportional hazard regression with recurrent events analyses. Robust variance estimates were applied to calculate confidence intervals. Cox proportional hazard regression with recurrent events (provision of CIRI care) allowed for consideration of more than one event per participant. This recurrent event analysis permitted the modeling of the length of time and allowed for an assessment of associations between recurrent events. This was appropriate as CIRI are typically acute, not chronic, infections. In addition, nursing care for CIRI often included debridement and dressing changes, which often need to be repeated; this type of analysis was well suited to this type of care regimen. Cox proportional hazard
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regression with recurrent events can also estimate valid standard errors in the presence of correlated data over time (22, 23). A counting process framework was used whereby individuals were considered to be at risk from time zero to first event, from first event to second event, and so forth. For all participants, time zero was defined as the date of recruitment into the Scientific Evaluation of Supervised Injection study. Participants who did not seek CIRI care were right censored at the end of January 31, 2008 or if one of the following occurred: the participant was lost to follow-up or moved out of province. The multivariate model was fit using an a priori defined model-building approach in which we adjusted for all variables that were statistically significant at p ! 0.05 in the bivariate analyses. All p values are two sided.
RESULTS By the end of January 2008, 1,083 individuals were enrolled in Scientific Evaluation of Supervised Injection and 901 (83%) had at least one follow-up visit. After examination of care patterns for all participants, three individuals were seen to have markedly different pattern of CIRI care: 73, 74, and 85 treatment episodes. The next most frequent number of times that CIRI care was received was 37 times; therefore, those three individuals were determined to be outliers and were excluded from all subsequent analyses. Among the remaining 1,080 study participants, the median age was 38.4 years (interquartile range [IQR]: 32.7–44.3), and 314 (29%) were female. The median follow-up duration after recruitment into the cohort was 21.4 months (IQR: 13.1–24.6). Two hundred ninety-six (27%) Scientific Evaluation of Supervised Injection participants received nursing care for a CIRI at the SIF. Importantly, the majority of visits to the nurse within the SIF were related to CIRI care (65%). Other reasons for nurse care included foot care (6%), respiratory care (3%), pregnancy test (2%), psychosocial support (7%), or other (17%) (data not shown). As shown in Table 1, Scientific Evaluation of Supervised Injection participants receiving CIRI care were more likely at baseline to be female (odds ratio [OR] Z 1.89 [95% confidence interval {CI): 1.35–2.63]), DTES residents (OR Z 1.75 [95% CI: 1.20–2.54]), daily cocaine injectors (OR Z 1.57 [95% CI: 1.13–2.19]), daily heroin injectors (OR Z 1.41 [95% CI: 1.02–1.95]), and daily speedball injectors (OR Z 1.96 [95% CI: 1.30–2.95]). During the study period (December 1, 2003 to January 31, 2008), the incidence density of Scientific Evaluation of Supervised Injection participants receiving CIRI care was 22.0 per 100 person-years (95% CI: 19.6–24.6). As displayed in Fig. 1, females were more likely to receive CIRI care
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TABLE 1. Baseline profile of Scientific Evaluation of Supervised Injection participants receiving CIRI care at the SIF Variable
No CIRI care, n Z 901 n (%)
CIRI care, n Z 179 n (%)
Age Median [IQR] 38.5 [32.9–44.3] 37.8 [29.5–44.4] Sex Female 241 (27%) 73 (41%) Male 660 (73%) 106 (59%) Unstable housing Yes 484 (54%) 484 (54%) No 417 (46%) 75 (42%) DTES residence* Yes 593 (66%) 138 (77%) No 308 (34%) 41 (23%) Require help to inject Yes 289 (32%) 67 (37%) No 612 (68%) 112 (63%) Cocaine injection* Daily 270 (30%) 72 (40%) Not daily 631 (70%) 107 (60%) Heroin injection* Daily 442 (49%) 103 (58%) Not daily 459 (51%) 76 (42%) Speedball injection* Daily 109 (12%) 38 (21%) Not daily 792 (88%) 141 (79%)
Odds ratio (95% CI) 0.99 (0.97–1.01) 1.89 (1.35–2.63)
1.19 (0.86–1.65)
1.75 (1.20–2.54)
1.27 (0.91–1.77)
1.57 (1.13–2.19)
1.41 (1.02–1.95)
1.96 (1.30–2.95)
SIF Z Supervised Injection Facility; CIRI Z cutaneous injected-related injection; CI Z confidence interval; IQR Z interquartile range; DTES Z Downtown Eastside. *Behaviors refer to activities in the last 6 months.
(incidence density 34.7 per 100 person-years [95% CI: 29.0–41.3]) as opposed to males (incidence density 17.5 per 100 person-years [95% CI: 15.1–20.3]). This result was statistically significant according to the log-rank test (p ! 0.01). Factors that were associated with receiving CIRI care in univariate analyses are shown in Table 2 in the Cox proportional hazard model. As displayed, being female (hazard ratio [HR] Z 2.08 [95% CI: 1.49–2.92]), living in unstable housing (HR Z 1.61 [95% CI: 1.17–2.22]), DTES residence (HR Z 1.68 [95% CI: 1.13–2.49]), and daily speedball injection (HR Z 1.92 [95% CI: 1.21–3.05]), were associated with receiving CIRI care in univariate analyses. When the coefficients were tested for time dependence, we found that the assumptions of the Cox analysis were met, except for the variable requiring help injecting. Therefore, in the multivariate analysis, an interaction term between requiring help injecting and logarithm of time was included. As displayed in Table 2, in the multivariate model, being female (AHR Z 1.87 [95% CI: 1.32–2.64]), living in unstable housing (AHR Z 1.39 [95% CI: 1.02–1.88]), and daily heroin injection (AHR Z 1.52 [95% CI: 1.13–2.04]) were independently associated with receiving CIRI care.
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TABLE 2. Univariate and multivariate Cox proportional hazard analyses of CIRI care among Scientific Evaluation of Supervised Injection participants (n Z 1,080)
Incidence of CIRI care (%)
45 40
Unadjusted HR
35 30 25 20 15 10 females males
5 0
407
0
6
12
18
24
Time (months)
FIGURE 1. Incidence of cutaneous injection-related infection (CIRI) care among Scientific Evaluation of Supervised Infection participants, stratified by sex (n Z 1,080; log–rank p ! 0.01).
We also considered an interaction term involving requiring help injecting and time; this interaction was found to be significant (AHR Z 1.25 [95% CI: 1.02–1.55]). Since homelessness may also be associated with our outcome but is likely collinear with the variable unstable housing, a subanalysis was conducted to examine the impact of homelessness on our outcome of interest. The multivariate results remained virtually unchanged (data not shown). In addition, given that HIV-positive IDU are known to have heightened susceptibility to CIRI, we conducted a subanalysis that considered the effect of HIV status. HIV status was not associated with receiving care for CIRI (p O 0.05), and HIV had virtually no impact on our multivariate model (data not shown).
DISCUSSION In the present study, 27% of Scientific Evaluation of Supervised Injection participants received CIRI care within the SIF. We found that being female, living in unstable housing, and daily heroin injection were independent predictors of receiving CIRI care among a cohort of IDU recruited from within Vancouver’s SIF. This paper is the first we are aware of to describe the epidemiology of CIRI care receipt within an SIF. Our finding that female sex was associated with receiving CIRI care at the SIF is consistent with previous work that has identified females as being more likely to seek medical treatment (24). In addition, females are at a heightened risk of CIRI development (25–29), and this may be due to smaller, less easily accessible veins (2). Furthermore, females are known to be particularly marginalized in drug-using relationships, such as being more likely to require assistance
AHR
Variable
HR
95% CI
HR
95% CI
Age (per year) Sex (female vs. male) Unstable housing* (yes vs. no) DTES residence* (yes vs. no) Cocaine injection* (daily vs. not daily) Heroin injection* (daily vs. not daily) Speedball injection* (daily vs. not daily)
0.99 2.08 1.61 1.68 1.14
0.97–1.00 1.49–2.92 1.17–2.22 1.13–2.49 0.82–1.58
1.87 1.39 1.33
1.32–2.64 1.02–1.88 0.90–1.96
1.82
1.37–2.42
1.52
1.13–2.04
1.92
1.21–3.05
1.47
0.95–2.26
CIRI Z cutaneous injected–related injection; SESI - Scientific Evaluation of Supervised Injection; HR Z hazard ratio; CI Z confidence interval; AHR Z adjusted hazard ratio; DTES Z Downtown Eastside. *Behaviors refer to activities in the last 6 months. Model was fit adjusted for all variables; p ! 0.05 in unadjusted analyses
with injection, which is a known marker of high-risk injection and associated with an increased risk of HIV and HCV transmission and CIRI (25, 26). Nevertheless, this finding demonstrates that female SIF users are accessing CIRI care at the SIF. This situation represents a unique opportunity for nurses to offer additional targeted care to this subpopulation. Individuals who live in unstable housing as well as daily heroin injectors were more likely to receive CIRI care at the SIF. Differences between the baseline and Cox proportional hazard regression results may be due to differences in the cross-sectional versus time-updated nature of the techniques. Research has demonstrated that among a DTES community-recruited cohort, participants who reported living in unstable housing and daily heroin injection were significantly more likely to use the SIF (21). Therefore, this result may simply reflect the fact that individuals who live in unstable housing and are daily heroin injectors are overrepresented in this sample. Alternatively, this finding may indicate that these particular individuals are more likely to receive CIRI care in this setting. Given that IDU remain a population medically underserved (29), this finding may be related to a proposed benefit of the SIF, whereby hard-to-reach IDU populations can be drawn into a healthcare setting so that service delivery to this population can be improved (17). Furthermore, it may be that individuals living in unstable housing may be unwilling to carry materials that can prevent CIRI, such as alcohol swabs, out of fear of confrontations with the police. While cocaine use has been associated with having a CIRI (26, 27), cocaine injection was not associated with receiving care for CIRI. This may be due to unique barriers to care that cocaine injectors face which could be, in part, related to greater intensity of injecting among cocaine injectors.
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Our study found that over time individuals who reported requiring help injecting were more likely to receive CIRI care. In general, this finding is consistent with previous research indicating that individuals who require help injecting are more likely to be inexperienced and inadequately educated on ways to inject safely (30). Further, a recent study on safer injecting education administered by nurses at the SIF reported that Scientific Evaluation of Supervised Injection participants who require help injecting are more likely to engage with nurses on education about injecting (31). Collectively, what these studies and our findings may suggest is that individuals who require help injecting, despite being at heightened risk of blood-borne disease transmission including HIV (32, 33), are engaging in nurse-administered care at the SIF. There are limitations of this research. First, these results are derived from an observational cohort and it is possible that unmeasured factors may explain our findings. For example, Scientific Evaluation of Supervised Injection participants who were more concerned for their health may have used the SIF more. However, previous research has suggested that greater use of the SIF is associated with markers of reduced access to care, including high-intensity drug injection and living in unstable housing (21). In addition, this study examined nursing care for CIRI at the SIF and we did not have existing information on other health service utilization in Vancouver’s DTES. Second, although our key end points were based on database linkages rather than self-report, our explanatory variables were based on selfreport; therefore the possibility of social desirability bias cannot be eliminated. Nevertheless, studies have suggested self-report among IDU to be valid (34). Third, although results from this study may be generalizable to SIF users in this and other settings, it is not appropriate to extend these findings to all IDU, either in the DTES or elsewhere. In conclusion, 27% of Scientific Evaluation of Supervised Injection participants received nursing care for a CIRI and we observed that the majority of care provided by the nursing staff at a local SIF was related to CIRI. Receiving CIRI care at the SIF was predicted by being female, living in unstable housing, and daily heroin injection. These results describe who is more likely to receive CIRI care, which is of use to those engaged with developing and improving policy and programs of comprehensive treatment regimens involving this population. The authors wish to thank the staff of the InSite SIF and Vancouver Coastal Health (Chris Buchner, David Marsh, Heather Hay). We also thank Aaron Eddie, Suzy Coulter, Megan Oleson, Sam Milligan, Peter Vann, Dave Isham, Steve Gaspar, and Deborah Graham for their research and administrative assistance. Particular thanks go to Daniel Kane for his assistance with data acquisition. The evaluation of the supervised injecting facility was originally made
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possible through a financial contribution from Health Canada, although the views expressed herein do not represent the official policies of Health Canada. The evaluation is currently supported by the Canadian Institutes of Health Research (HPR-85526 and RAA-79918) and Vancouver Coastal Health. T.K. and E.L.S. are supported by the Michael Smith Foundation for Health Research and the Canadian Institutes of Health Research. M.W.T. is supported by the Michael Smith Foundation for Health Research. Funding agencies had no role in study design, data collection, analysis or writing of the report, nor did they have a role in the decision to submit the paper for publication.
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PURPOSE: To evaluate the factors associated with receiving cutaneous injection-related infection (CIRI) care among a representative cohort of supervised injecting facility (SIF) users. METHODS: Data were collected biannually as part of a prospective cohort, the Scientific Evaluation of Supervised Injection study. Kaplan-Meier methods and Cox proportional hazards regression with recurrent events were used to examine incidence and factors associated with CIRI care, respectively. RESULTS: One thousand eighty individuals were recruited between December 1, 2003 and January 31, 2008. The incidence density of participants receiving CIRI care was 22.0 per 100 person-years (95% confidence interval [CI]: 19.6–24.6). In the adjusted Cox proportional hazard model, female sex (adjusted hazard ratio [AHR] Z 1.87 [95% CI: 1.32–2.64]), unstable housing (AHR Z 1.39 [95% CI: 1.02–1.88]), and daily heroin injection (AHR Z 1.52 [95% CI: 1.13–2.04]) were independently associated with receiving CIRI care at the SIF. CONCLUSIONS: These results describe who is more likely to receive CIRI care, which is of use to those engaged with policy and practice of treatment regimens involving this population. Ann Epidemiol 2009;19:404–409. Ó 2009 Elsevier Inc. All rights reserved. KEY WORDS:
Statistical Methods, Infectious Disease, Nursing, IV Drug User.
INTRODUCTION Cutaneous injection–related infections (CIRI), which includes abscesses and cellulitis, are prevalent among persons who inject drugs (IDU) (1, 2). Although these infections are known to constitute a primary cause of morbidity among IDU (2, 3), there is a paucity of research in this area (4). Most of the literature on the treatment of CIRI has been derived from hospital- and emergency department (ED)–based chart reviews, and most has been carried out in the United States (5–9). Financially the burden of CIRI in the medical system is substantial. A general hospital in San Francisco reported a conservative estimate of ED costs in excess of $20 million per year (10). Several models of care have been shown to effectively incorporate both CIRI treatment and wound care and to result in cost savings (8, 11, 12). In San Francisco, the Integrated Soft Tissue Infection Services (ISIS) clinic has been
British Columbia Centre for Excellence in HIV/AIDS (E.L.S., E.W., R.Z., M.W.T., J.S.M.), School of Population and Public Health (E.L.S., M.W.T.), Department of Medicine (E.W., J.S.M, T.K.), University of British Columbia, Vancouver, Canada. Address correspondence to: Thomas Kerr, BC Centre for Excellence in HIV/AIDS, St. Paul’s Hospital 608-1081 Burrard St, Vancouver, BC V6Z 1Y6, Canada. Tel: (604) 806-9116. fax: (604) 806-9044. E-mail: uhri@ cfenet.ubc.ca. Received September 8, 2008; accepted March 2, 2009. Ó 2009 Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010
found to be a valuable and cost saving program (8). The program has changed a predominantly inpatient model to that of an outpatient model of care that offers surgical interventions, counseling, and social services for individuals with soft tissue infections (8). In the first year of operation, results from the clinic reported a 47% decrease in surgical service hospital admissions, a 34% reduction in ED visits, and an estimated savings of over $8 million (8). Another example of effective treatment for CIRI outside the hospital setting is a wound management clinic that operates in conjunction with a syringe exchange program in New Haven (12). Notably, individuals who access syringe exchange programs that provide primary care services have reported reduced ED utilization (13). Medically supervised safer injection facilities (SIF), where IDU can inject pre-obtained illicit drugs under the supervision of medical staff, operate in several cities in Europe, and in Sydney, Australia (14–16). Within SIFs, individuals are typically provided with sterile injecting equipment and emergency intervention in the event of an accidental overdose, as well as medical care and addiction treatment, either on site or through referral (17, 18). On September 22, 2003, Vancouver, Canada opened North America’s first government sanctioned SIF (14). The objectives of this study were to examine receiving CIRI care as well as factors associated with receiving CIRI care among users of Vancouver’s SIF. 1047-2797/09/$–see front matter doi:10.1016/j.annepidem.2009.03.007
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Selected Abbreviations and Acronyms CIRI Z cutaneous injection-related infection IDU Z injection drug user ED Z emergency department ISIS Z Integrated Soft Tissue Infection Services SIF Z safer injection facilities DTES Z Downtown Eastside IQR Z interquartile range HR Z hazard ratio AHR Z adjusted hazard ratio
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supplies for CIRI, including ‘alleyn’, ‘combiderm’, ‘mesalt’, and ‘iodasorb’. Multiple visits per participant were counted except if a participant had more than one CIRI care episode in one day. In this case, only the first CIRI care event was counted (i.e., one CIRI care episode considered per day). Multiple visits for each participant reflect that CIRI care by nurses often involves numerous visits per infection plus more than one infection per participant during the study period. Statistical Analysis
METHODS Study Sample The Vancouver SIF is being evaluated through the Scientific Evaluation of Supervised Injection study, a prospective cohort that has been described in detail previously (19). The SIF is located in Vancouver’s Downtown Eastside (DTES), which is the epicenter of Vancouver’s IDU population, known as one of the poorest urban postal codes in Canada. The neighborhood is also home to a large open drug and sex work scene and the site of an explosive epidemic of HIV infection. Briefly, since December 2003 participants were recruited during random times from within the SIF. SIF users were eligible to be randomized for selection by the SIF’s intake computer after their second visit. Among individuals who were recruited, an interviewer-administered questionnaire elicited sociodemographic and behavioral information. In addition, participants completed a nurseadministered questionnaire regarding health status and provided venous blood samples for hepatitis C virus and HIV at baseline and at semiannual follow-up visits. Interviewees received CAD$20 for their participation. The SIF intake computer is equipped with a database that tracks utilization of services within the facility (e.g., care by nurse, sessions with addictions counselor) as well as referrals to other services (e.g., hospital or detoxification services) (19). Informed consent was obtained from all participants. The Research Ethics Board at the University of British Columbia approved the present study. Study Outcome The end point in this study was the provision of care at the SIF. Both abscesses and cellulitis were considered to be CIRI. The occurrence of CIRI care events was determined by examining relevant entries by the nurse in the SIF database. Specifically, instances of CIRI care were identified by searching the SIF database for (1) entries describing the provision of care by a nurse for an abscess, a wound, or a skin infection; (2) notes containing ‘abscess’, ‘cellulitis’; or (3) entries describing the provision of nursing care
As an initial step, we examined the total number of CIRI care events at the SIF reported by each participant. We also examined the sociodemographic and behavioral variables, collected as part of the baseline Scientific Evaluation of Supervised Injection questionnaire, stratified by whether receiving CIRI care was or was not obtained at the SIF. Potential explanatory factors considered in subsequent analyses included the following: age, sex (female vs. male), living in unstable housing (yes vs. no), DTES residence (yes vs. no), requiring help injecting (yes vs. no), daily cocaine injection (yes vs. no), daily heroin injection (yes vs. no), and daily speedball injection (yes vs. no). Unstable housing was defined as living in a single room occupancy hotel, shelter, recovery or transition house, jail, on the street, or having no fixed address. Requiring help injecting was based on the question ‘‘Have you needed someone to help you inject?’’ Daily injection of cocaine, heroin, and speedball refers to at least once-daily injection. Behavioral variables referred to self-reported activity in the last 6 months. Variable definitions have been used in previous studies (20, 21). Categorical variables were analyzed using chi-square tests and continuous variables were analyzed by the Wilcoxon rank sum test. The incidence of CIRI care, stratified by sex, was estimated by using Kaplan-Meier methods. Kaplan-Meier curves were compared by the log-rank test. Significant differences (p value ! 0.05) between participants who did and did not receive CIRI care determined variable selection for the unadjusted and adjusted Cox proportional hazard regression with recurrent events analyses. Robust variance estimates were applied to calculate confidence intervals. Cox proportional hazard regression with recurrent events (provision of CIRI care) allowed for consideration of more than one event per participant. This recurrent event analysis permitted the modeling of the length of time and allowed for an assessment of associations between recurrent events. This was appropriate as CIRI are typically acute, not chronic, infections. In addition, nursing care for CIRI often included debridement and dressing changes, which often need to be repeated; this type of analysis was well suited to this type of care regimen. Cox proportional hazard
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regression with recurrent events can also estimate valid standard errors in the presence of correlated data over time (22, 23). A counting process framework was used whereby individuals were considered to be at risk from time zero to first event, from first event to second event, and so forth. For all participants, time zero was defined as the date of recruitment into the Scientific Evaluation of Supervised Injection study. Participants who did not seek CIRI care were right censored at the end of January 31, 2008 or if one of the following occurred: the participant was lost to follow-up or moved out of province. The multivariate model was fit using an a priori defined model-building approach in which we adjusted for all variables that were statistically significant at p ! 0.05 in the bivariate analyses. All p values are two sided.
RESULTS By the end of January 2008, 1,083 individuals were enrolled in Scientific Evaluation of Supervised Injection and 901 (83%) had at least one follow-up visit. After examination of care patterns for all participants, three individuals were seen to have markedly different pattern of CIRI care: 73, 74, and 85 treatment episodes. The next most frequent number of times that CIRI care was received was 37 times; therefore, those three individuals were determined to be outliers and were excluded from all subsequent analyses. Among the remaining 1,080 study participants, the median age was 38.4 years (interquartile range [IQR]: 32.7–44.3), and 314 (29%) were female. The median follow-up duration after recruitment into the cohort was 21.4 months (IQR: 13.1–24.6). Two hundred ninety-six (27%) Scientific Evaluation of Supervised Injection participants received nursing care for a CIRI at the SIF. Importantly, the majority of visits to the nurse within the SIF were related to CIRI care (65%). Other reasons for nurse care included foot care (6%), respiratory care (3%), pregnancy test (2%), psychosocial support (7%), or other (17%) (data not shown). As shown in Table 1, Scientific Evaluation of Supervised Injection participants receiving CIRI care were more likely at baseline to be female (odds ratio [OR] Z 1.89 [95% confidence interval {CI): 1.35–2.63]), DTES residents (OR Z 1.75 [95% CI: 1.20–2.54]), daily cocaine injectors (OR Z 1.57 [95% CI: 1.13–2.19]), daily heroin injectors (OR Z 1.41 [95% CI: 1.02–1.95]), and daily speedball injectors (OR Z 1.96 [95% CI: 1.30–2.95]). During the study period (December 1, 2003 to January 31, 2008), the incidence density of Scientific Evaluation of Supervised Injection participants receiving CIRI care was 22.0 per 100 person-years (95% CI: 19.6–24.6). As displayed in Fig. 1, females were more likely to receive CIRI care
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TABLE 1. Baseline profile of Scientific Evaluation of Supervised Injection participants receiving CIRI care at the SIF Variable
No CIRI care, n Z 901 n (%)
CIRI care, n Z 179 n (%)
Age Median [IQR] 38.5 [32.9–44.3] 37.8 [29.5–44.4] Sex Female 241 (27%) 73 (41%) Male 660 (73%) 106 (59%) Unstable housing Yes 484 (54%) 484 (54%) No 417 (46%) 75 (42%) DTES residence* Yes 593 (66%) 138 (77%) No 308 (34%) 41 (23%) Require help to inject Yes 289 (32%) 67 (37%) No 612 (68%) 112 (63%) Cocaine injection* Daily 270 (30%) 72 (40%) Not daily 631 (70%) 107 (60%) Heroin injection* Daily 442 (49%) 103 (58%) Not daily 459 (51%) 76 (42%) Speedball injection* Daily 109 (12%) 38 (21%) Not daily 792 (88%) 141 (79%)
Odds ratio (95% CI) 0.99 (0.97–1.01) 1.89 (1.35–2.63)
1.19 (0.86–1.65)
1.75 (1.20–2.54)
1.27 (0.91–1.77)
1.57 (1.13–2.19)
1.41 (1.02–1.95)
1.96 (1.30–2.95)
SIF Z Supervised Injection Facility; CIRI Z cutaneous injected-related injection; CI Z confidence interval; IQR Z interquartile range; DTES Z Downtown Eastside. *Behaviors refer to activities in the last 6 months.
(incidence density 34.7 per 100 person-years [95% CI: 29.0–41.3]) as opposed to males (incidence density 17.5 per 100 person-years [95% CI: 15.1–20.3]). This result was statistically significant according to the log-rank test (p ! 0.01). Factors that were associated with receiving CIRI care in univariate analyses are shown in Table 2 in the Cox proportional hazard model. As displayed, being female (hazard ratio [HR] Z 2.08 [95% CI: 1.49–2.92]), living in unstable housing (HR Z 1.61 [95% CI: 1.17–2.22]), DTES residence (HR Z 1.68 [95% CI: 1.13–2.49]), and daily speedball injection (HR Z 1.92 [95% CI: 1.21–3.05]), were associated with receiving CIRI care in univariate analyses. When the coefficients were tested for time dependence, we found that the assumptions of the Cox analysis were met, except for the variable requiring help injecting. Therefore, in the multivariate analysis, an interaction term between requiring help injecting and logarithm of time was included. As displayed in Table 2, in the multivariate model, being female (AHR Z 1.87 [95% CI: 1.32–2.64]), living in unstable housing (AHR Z 1.39 [95% CI: 1.02–1.88]), and daily heroin injection (AHR Z 1.52 [95% CI: 1.13–2.04]) were independently associated with receiving CIRI care.
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TABLE 2. Univariate and multivariate Cox proportional hazard analyses of CIRI care among Scientific Evaluation of Supervised Injection participants (n Z 1,080)
Incidence of CIRI care (%)
45 40
Unadjusted HR
35 30 25 20 15 10 females males
5 0
407
0
6
12
18
24
Time (months)
FIGURE 1. Incidence of cutaneous injection-related infection (CIRI) care among Scientific Evaluation of Supervised Infection participants, stratified by sex (n Z 1,080; log–rank p ! 0.01).
We also considered an interaction term involving requiring help injecting and time; this interaction was found to be significant (AHR Z 1.25 [95% CI: 1.02–1.55]). Since homelessness may also be associated with our outcome but is likely collinear with the variable unstable housing, a subanalysis was conducted to examine the impact of homelessness on our outcome of interest. The multivariate results remained virtually unchanged (data not shown). In addition, given that HIV-positive IDU are known to have heightened susceptibility to CIRI, we conducted a subanalysis that considered the effect of HIV status. HIV status was not associated with receiving care for CIRI (p O 0.05), and HIV had virtually no impact on our multivariate model (data not shown).
DISCUSSION In the present study, 27% of Scientific Evaluation of Supervised Injection participants received CIRI care within the SIF. We found that being female, living in unstable housing, and daily heroin injection were independent predictors of receiving CIRI care among a cohort of IDU recruited from within Vancouver’s SIF. This paper is the first we are aware of to describe the epidemiology of CIRI care receipt within an SIF. Our finding that female sex was associated with receiving CIRI care at the SIF is consistent with previous work that has identified females as being more likely to seek medical treatment (24). In addition, females are at a heightened risk of CIRI development (25–29), and this may be due to smaller, less easily accessible veins (2). Furthermore, females are known to be particularly marginalized in drug-using relationships, such as being more likely to require assistance
AHR
Variable
HR
95% CI
HR
95% CI
Age (per year) Sex (female vs. male) Unstable housing* (yes vs. no) DTES residence* (yes vs. no) Cocaine injection* (daily vs. not daily) Heroin injection* (daily vs. not daily) Speedball injection* (daily vs. not daily)
0.99 2.08 1.61 1.68 1.14
0.97–1.00 1.49–2.92 1.17–2.22 1.13–2.49 0.82–1.58
1.87 1.39 1.33
1.32–2.64 1.02–1.88 0.90–1.96
1.82
1.37–2.42
1.52
1.13–2.04
1.92
1.21–3.05
1.47
0.95–2.26
CIRI Z cutaneous injected–related injection; SESI - Scientific Evaluation of Supervised Injection; HR Z hazard ratio; CI Z confidence interval; AHR Z adjusted hazard ratio; DTES Z Downtown Eastside. *Behaviors refer to activities in the last 6 months. Model was fit adjusted for all variables; p ! 0.05 in unadjusted analyses
with injection, which is a known marker of high-risk injection and associated with an increased risk of HIV and HCV transmission and CIRI (25, 26). Nevertheless, this finding demonstrates that female SIF users are accessing CIRI care at the SIF. This situation represents a unique opportunity for nurses to offer additional targeted care to this subpopulation. Individuals who live in unstable housing as well as daily heroin injectors were more likely to receive CIRI care at the SIF. Differences between the baseline and Cox proportional hazard regression results may be due to differences in the cross-sectional versus time-updated nature of the techniques. Research has demonstrated that among a DTES community-recruited cohort, participants who reported living in unstable housing and daily heroin injection were significantly more likely to use the SIF (21). Therefore, this result may simply reflect the fact that individuals who live in unstable housing and are daily heroin injectors are overrepresented in this sample. Alternatively, this finding may indicate that these particular individuals are more likely to receive CIRI care in this setting. Given that IDU remain a population medically underserved (29), this finding may be related to a proposed benefit of the SIF, whereby hard-to-reach IDU populations can be drawn into a healthcare setting so that service delivery to this population can be improved (17). Furthermore, it may be that individuals living in unstable housing may be unwilling to carry materials that can prevent CIRI, such as alcohol swabs, out of fear of confrontations with the police. While cocaine use has been associated with having a CIRI (26, 27), cocaine injection was not associated with receiving care for CIRI. This may be due to unique barriers to care that cocaine injectors face which could be, in part, related to greater intensity of injecting among cocaine injectors.
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Our study found that over time individuals who reported requiring help injecting were more likely to receive CIRI care. In general, this finding is consistent with previous research indicating that individuals who require help injecting are more likely to be inexperienced and inadequately educated on ways to inject safely (30). Further, a recent study on safer injecting education administered by nurses at the SIF reported that Scientific Evaluation of Supervised Injection participants who require help injecting are more likely to engage with nurses on education about injecting (31). Collectively, what these studies and our findings may suggest is that individuals who require help injecting, despite being at heightened risk of blood-borne disease transmission including HIV (32, 33), are engaging in nurse-administered care at the SIF. There are limitations of this research. First, these results are derived from an observational cohort and it is possible that unmeasured factors may explain our findings. For example, Scientific Evaluation of Supervised Injection participants who were more concerned for their health may have used the SIF more. However, previous research has suggested that greater use of the SIF is associated with markers of reduced access to care, including high-intensity drug injection and living in unstable housing (21). In addition, this study examined nursing care for CIRI at the SIF and we did not have existing information on other health service utilization in Vancouver’s DTES. Second, although our key end points were based on database linkages rather than self-report, our explanatory variables were based on selfreport; therefore the possibility of social desirability bias cannot be eliminated. Nevertheless, studies have suggested self-report among IDU to be valid (34). Third, although results from this study may be generalizable to SIF users in this and other settings, it is not appropriate to extend these findings to all IDU, either in the DTES or elsewhere. In conclusion, 27% of Scientific Evaluation of Supervised Injection participants received nursing care for a CIRI and we observed that the majority of care provided by the nursing staff at a local SIF was related to CIRI. Receiving CIRI care at the SIF was predicted by being female, living in unstable housing, and daily heroin injection. These results describe who is more likely to receive CIRI care, which is of use to those engaged with developing and improving policy and programs of comprehensive treatment regimens involving this population. The authors wish to thank the staff of the InSite SIF and Vancouver Coastal Health (Chris Buchner, David Marsh, Heather Hay). We also thank Aaron Eddie, Suzy Coulter, Megan Oleson, Sam Milligan, Peter Vann, Dave Isham, Steve Gaspar, and Deborah Graham for their research and administrative assistance. Particular thanks go to Daniel Kane for his assistance with data acquisition. The evaluation of the supervised injecting facility was originally made
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possible through a financial contribution from Health Canada, although the views expressed herein do not represent the official policies of Health Canada. The evaluation is currently supported by the Canadian Institutes of Health Research (HPR-85526 and RAA-79918) and Vancouver Coastal Health. T.K. and E.L.S. are supported by the Michael Smith Foundation for Health Research and the Canadian Institutes of Health Research. M.W.T. is supported by the Michael Smith Foundation for Health Research. Funding agencies had no role in study design, data collection, analysis or writing of the report, nor did they have a role in the decision to submit the paper for publication.
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