Association of hospital-based substance use supports on emergency department revisits: a retrospective cohort study in Sudbury, Canada from 2018 to 2022.

BACKGROUND: This study compares emergency department (ED) revisits for patients receiving hospital-based substance-use support compared to those who did not receive specialized addiction services at Health Sciences North in Sudbury, Ontario, Canada. METHODS: The study is a retrospective observational study using administrative data from all patients presenting with substance use disorder (SUD) at Health Sciences North from January 1, 2018, and August 31, 2022 with ICD-10 codes from the Discharge Abstract Database (DAD) and the National Ambulatory Care Database (NACRS). There were two interventions under study: addiction medicine consult services (AMCS group), and specialized addiction medicine unit (AMU group). The AMCS is a consult service offered for patients in the ED and those who are admitted to the hospital. The AMU is a specialized inpatient medical unit designed to offer addiction support to stabilize patients that operates under a harm-reduction philosophy. The primary outcome was all cause ED revisit within 30 days of the index ED or hospital visit. The secondary outcome was all observed ED revisits in the study period. Kaplan-Meier curves were used to measure the proportion of 30-day revisits by exposure group. Odds ratios and Hazard Ratios were calculated using logistic regression models with random effects and Cox-proportional hazard model respectively. RESULTS: A total of 5,367 patients with 10,871 ED index visits, and 2,127 revisits between 2018 and 2022 are included in the study. 45% (2,340/5,367) of patient were not admitted to hospital. 30-day revisits were less likely among the intervention group: Addiction Medicine Consult Services (AMCS) in the ED significantly reduced the odds of revisits (OR 0.53, 95% CI 0.39-0.71, p < 0.01) and first revisits (OR 0.42, 95% CI 0.33-0.53, p < 0.01). The AMU group was associated with lower revisits odds (OR 0.80, 95% CI 0.66-0.98, p = 0.03). For every additional year of age, the odds of revisits slightly decreased (OR 0.99, 95% CI 0.98-1.00, p = 0.01) and males were found to have an increased risk compared to females (OR 1.50, 95% CI 1.35-1.67, p < 0.01). INTERPRETATION: We observe statistically significant differences in ED revisits for patients receiving hospital-based substance-use support at Health Sciences North. Hospital-based substance-use supports could be applied to other hospitals to reduce 30-day revisits.

Evaluating an addiction medicine unit in Sudbury, Ontario Canada: a mixed-methods study protocol.

BACKGROUND: In response to the escalating global prevalence of substance use and the specific challenges faced in Northern Ontario, Canada, an Addiction Medicine Unit (AMU) was established at Health Sciences North (HSN) in Sudbury. This protocol outlines the approach for a comprehensive evaluation of the AMU, with the aim of assessing its impact on patient outcomes, healthcare utilization, and staff perspectives. METHODS: We conducted a parallel mixed-method study that encompassed the analysis of single-center-level administrative health data and primary data collection, including a longitudinal observational study (target n = 1,200), pre- and post-admission quantitative interviews (target n = 100), and qualitative interviews (target n = 25 patients and n = 15 staff). We implemented a participatory approach to this evaluation, collaborating with individuals who possess lived or living expertise in drug use, frontline staff, and decision-makers across the hospital. Data analysis methods encompass a range of statistical techniques, including logistic regression models, Cox proportional hazards models, Kaplan-Meier curves, Generalized Estimating Equations (GEE), and thematic qualitative analysis, ensuring a robust evaluation of patient outcomes and healthcare utilization. DISCUSSION: This protocol serves as the foundation for a comprehensive assessment designed to provide insights into the AMU's effectiveness in addressing substance use-related challenges, reducing healthcare disparities, and improving patient outcomes. All study procedures have been meticulously designed to align with the ethical principles outlined in the Tri-Council Policy Statement: Ethical Conduct for Research Involving Humans. The findings will be disseminated progressively through committees and working groups established for this research, and subsequently published in peer-reviewed journals. Anticipated outcomes include informing evidence-based healthcare decision-making and driving improvements in addiction treatment practices within healthcare settings.

Measuring treatment attrition at various stages of engagement in Opioid Agonist Treatment in Ontario Canada using a cascade of care framework.

BACKGROUND: The cascade of care framework is an effective way to measure attrition at various stages of engagement in Opioid Agonist Treatment (OAT). The primary objective of the study was to describe the cascade of care for patients who have accessed OAT from a network of specialized addiction clinics in Ontario, Canada. The secondary objectives were to evaluate correlates associated with retention in OAT at various stages and the impact of patients' location of the residence on retention in OAT. DESIGN: A multi-clinic retrospective cohort study was conducted using electronic medical record (EMR) data from the largest network of OAT clinics in Canada (70 clinics) from 2014 to 2020. Study participants included all patients who received OAT from the network of clinics during the study period. MEASUREMENTS: In this study, four stages of the cascade of care framework were operationalized to identify treatment engagement patterns, including patients retained within 90 days, 90 to 365 days, one to 2 years, and more than 2 years. Correlates associated with OAT retention for 90 days, 90 to 365 days, 1 to 2 years, and more than 2 years were also evaluated and compared across rural and urban areas in northern and southern Ontario. RESULTS: A total of 32,487 patients were included in the study. Compared to patients who were retained in OAT for 90 days, patients who were retained for 90 to 365 days, 1 to 2 years, or more than 2 years were more likely to have a higher number of treatment attempts, a higher number of average monthly urine drug screening and a lower proportion of positive urine drug screening results for other drug use. CONCLUSION: Distinct sociodemographic and clinical factors are likely to influence treatment retention at various stages of engagement along the OAT continuum. Research is required to determine if tailored strategies specific to people at different stages of retention have the potential to improve outcomes of OAT.

A Retrospective Cohort Study Comparing In-Person and Telemedicine-Based Opioid Agonist Treatment in Ontario, Canada, Using Administrative Health Data.

BACKGROUND: This study evaluated how telemedicine as a modality for opioid agonist treatment compares to in-person care. METHODS: We conducted a retrospective cohort study of patients enrolled in opioid agonist treatment between January 1, 2011, and December 31, 2015, in Ontario, Canada. We compared patients who received opioid agonist treatment predominantly in person, mixed, and predominantly by telemedicine. We used a logistic regression model to evaluate mortality, a Cox proportional hazard model to assess retention, and a negative binomial regression model to evaluate emergency department visits and hospitalizations. The study was performed using administrative health data with physician billing data from the Ontario Health Insurance Plan and prescription data from the Ontario Drug Benefit databases. RESULTS: A total of 55,924 individuals were included in the study. Receiving opioid agonist treatment by predominantly telemedicine was not associated with all-cause mortality (OR = 0.9, 95% CI: 0.8-1.0), 1-year treatment retention (OR = 1.0, 95% CI: 0.9-1.1), or opioid-related emergency department visits and hospitalizations when compared to in-person care. The rate of emergency department visits (IRR = 1.4), the rate of mental health-related emergency department visits (IRR = 1.5), and the rate of mental health-related hospitalizations per year (IRR = 1.2) was higher for patients who received opioid agonist treatment predominantly by telemedicine compared to in person. CONCLUSION: Our findings support the conclusion that telemedicine is equal to in-person care regarding mortality opioid-related emergency department visits and retention, and is a viable option for those seeking opioid agonist treatment.

A cohort study evaluating the association between concurrent mental disorders, mortality, morbidity, and continuous treatment retention for patients in opioid agonist treatment (OAT) across Ontario, Canada, using administrative health data.

BACKGROUND: Due to the high prevalence of mental disorders among people with opioid use disorder, the objective of this study was to determine the association between concurrent mental disorders, mortality, morbidity, and continuous treatment retention for patients in opioid agonist treatment in Ontario, Canada. METHODS: We conducted a retrospective cohort study of patients enrolled in opioid agonist treatment between January 1, 2011, and December 31, 2015. Patients were stratified into two groups: those diagnosed with concurrent mental disorders and opioid use disorder and those with opioid use disorder only, using data from the Ontario Health Insurance Plan Database, Ontario Drug Benefit Plan Database. The primary outcome studied was all-cause mortality using data from the Registered Persons Database. Emergency department visits from the National Ambulatory Care Database, hospitalizations Discharge Abstract Database, and continuous retention in treatment, defined as 1 year of uninterrupted opioid agonist treatment using data from the Ontario Drug Benefit Plan Database were measured as secondary outcomes. Encrypted patient identifiers were used to link information across databases. RESULTS: We identified 55,924 individuals enrolled in opioid agonist treatment, and 87% had a concurrent mental disorder diagnosis during this period. We observed that having a mental disorder was associated with an increased likelihood of all-cause mortality (odds ratio (OR) 1.4; 95% confidence interval (CI) 1.2-1.5). For patients diagnosed with mental disorders, the estimated rate of ED visits per year was 2.25 times higher and estimated rate of hospitalization per year was 1.67 times higher than for patients with no mental disorders. However, there was no association between having a diagnosis of a mental disorder and 1-year treatment retention in OAT-adjusted hazard ratio (HR) = 1.0; 95% CI 0.9 to 1.1. CONCLUSION: Our findings highlight the consequences of the high prevalence of mental disorders for individuals with opioid use disorder in Ontario, Canada.

The State of Opioid Agonist Therapy in Canada 20 Years after Federal Oversight.

Opioid agonist therapy was introduced in Canada in 1959 with the use of methadone for the treatment of opioid dependence. The regulation of methadone was the responsibility of Health Canada until 1995, when oversight was transferred to the provincial health systems. During the more than 20 years since the federal health authority transferred oversight of methadone to the provincial level, methadone programming has evolved differently in every province. The landscape of opioid dependence treatment is varied across the country, with generally increasing treatment capacity in all provinces and dramatic increases in some. Each province has an independent methadone program with differing policies, contingency management strategies, laboratory monitoring policies, and delivery methods. Treatment options have increased, with buprenorphine- and heroin-assisted treatment becoming available to limited degrees. Despite this, access remains a challenge in many parts of the country (particularly rural and remote areas) because the demand for treatment has increased even more rapidly than the capacity. Although treatment access remains a priority in many jurisdictions, there is also a need to attend to treatment quality as treatment access expands, including integration with addiction counselling, primary care, and mental health care. As well, coordinated monitoring and reporting of treatment need, quality, and delivery are required; implementing a national policy to promote planning would have tremendous value.

Automated image analysis programs for the quantification of microvascular network characteristics.

The majority of reports in which microvascular network properties are quantified rely on manual measurements, which are time consuming to collect and somewhat subjective. Despite some progress in creating automated image analysis techniques, the parameters measured by these methods are limited. For example, no automated system has yet been able to measure support cell recruitment, which is an important indicator of microvascular maturity. Microvessel alignment is another parameter that existing programs have not measured, despite a strong dependence of performance on alignment in some tissues. Here we present two image analysis programs, a semi-automated program that analyzes cross sections of microvascular networks and a fully automated program that analyzes images of whole mount preparations. Both programs quantify standard characteristics as well as support cell recruitment and microvascular network alignment, and were highly accurate in comparison to manual measurements for engineered tissues containing self-assembled microvessels.

A mathematical model for understanding fluid flow through engineered tissues containing microvessels.

Knowledge is limited about fluid flow in tissues containing engineered microvessels, which can be substantially different in topology than native capillary networks. A need exists for a computational model that allows for flow through tissues dense in nonpercolating and possibly nonperfusable microvessels to be efficiently evaluated. A finite difference (FD) model based on Poiseuille flow through a distribution of straight tubes acting as point sources and sinks, and Darcy flow through the interstitium, was developed to describe fluid flow through a tissue containing engineered microvessels. Accuracy of the FD model was assessed by comparison to a finite element (FE) model for the case of a single tube. Because the case of interest is a tissue with microvessels aligned with the flow, accuracy was also assessed in depth for a corresponding 2D FD model. The potential utility of the 2D FD model was then explored by correlating metrics of flow through the model tissue to microvessel morphometric properties. The results indicate that the model can predict the density of perfused microvessels based on parameters that can be easily measured.

In vitro models of angiogenesis and vasculogenesis in fibrin gel.

In vitro models of endothelial assembly into microvessels are useful for the study of angiogenesis and vasculogenesis. In addition, such models may be used to provide the microvasculature required to sustain engineered tissues. A large range of in vitro models of both angiogenesis and vasculogenesis have utilized fibrin gel as a scaffold. Although fibrin gel is conducive to endothelial assembly, its ultrastructure varies substantially based on the gel formulation and gelation conditions, making it challenging to compare between models. This work reviews existing models of endothelial assembly in fibrin gel and posits that differerences between models are partially caused by microstructural differences in fibrin gel.

Canadian Addiction Treatment Centre (CATC) opioid agonist treatment cohort in Ontario, Canada.

PURPOSE: The Canadian Addiction Treatment Centre (CATC) cohort was established during a period of increased provision of opioid agonist treatment (OAT), to study patient outcomes and trends related to the treatment of opioid use disorder (OUD) in Canada. The CATC cohort's strengths lie in its unique physician network, shared care model and event-level data, making it valuable for validation and integration studies. The CATC cohort is a valuable resource for examining OAT outcomes, providing insights into substance use trends and the impact of service-level factors. PARTICIPANTS: The CATC cohort comprises 32 246 people who received OAT prescriptions between April 2014 and February 2021, with ongoing tri-annual updates planned until 2027. The cohort includes data from all CATC clinics' electronic medical records and includes demographic information and OAT clinical indicators. FINDINGS TO DATE: This cohort profile describes the demographic and clinical characteristics of patients being treated in a large OAT physician network. As well, we report the longitudinal OAT retention by treatment type during a time of increasing exposure to a contaminated dangerous drug supply. Notable findings also include retention differences between methadone (32% of patients at 1 year) and buprenorphine (20% at 1 year). Previously published research from this cohort indicated that patient-level factors associated with retention include geographic location, concurrent substance use and prior treatment attempts. Service-level factors such as telemedicine delivery and frequency of urine drug screenings also influence retention. Additionally, the cohort identified rising OAT participation and a substantial increase in fentanyl use during the COVID-19 pandemic. FUTURE PLANS: Future research objectives are the longitudinal evaluation of retention and flexible modelling techniques that account for the changes as patients are treated with OAT. Furthermore, future research aims are the use of conditional models, and linkage with provincial-level administrative datasets.

The Patient Perspective of an Inpatient Addiction Medicine Unit Implemented in an Urban Northern Acute Care Hospital in Ontario, Canada.

Background: An Addiction Medicine Unit (AMU) represents a promising approach to enhancing hospital care for individuals who use substances, but there is limited research to understand patients' perspectives on AMUs. Therefore, the study objectives involved exploring patients' experiences with the AMU. Methods: Qualitative semi-structured interviews were conducted with 17 patients to gather their perspectives about the AMU. The AMU offers specialized inpatient addiction support, integrating medical and psychosocial interventions while facilitating connections to community supports to stabilize patients and manage addiction-related issues using a harm reduction philosophy. Results: Factors identified by patients that lead to positive experiences with the AMU included: efficient access to high-quality acute medical care, specialized addiction care, and additional support for non-medical needs. Patients emphasized the benefits of having peer support workers on staff, the overall positive interactions with staff, and how different these experiences were from their hospital admissions outside of the AMU. Factors identified by patients that should be considered in an AMU included: the ease of access to substances, negative interactions with other patients, and self-stigma/internalized discrimination. Also, the patient perspective reflected varied views on harm reduction. Patients' perception of the impact of an AMU overall reflected that the AMU is an effective way to deliver comprehensive treatment, to address the needs of PWUS, both medical and substance-use-related issues. They identified that the unit's intentional harm reduction philosophy facilitated access to care and positive patient-staff interactions, emphasizing the unit's progress in reducing fear and judgment and rebuilding trust in the healthcare system. Conclusion: The introduction of a new AMU in a Northern urban acute care hospital in Ontario has yielded positive patient experiences. The AMU model shows potential to re-establish trust between patients and providers, but ongoing efforts are needed to address underlying stigma to be more effective.

Aligned human microvessels formed in 3D fibrin gel by constraint of gel contraction.

This study aimed to form microvessels in fibrin gels, which is of interest both for studying the fundamental cell-matrix interactions as well as for tissue engineering purposes, and to align the microvessels, which would provide natural inlet and outlet sides for perfusion. The data reported here demonstrate the formation of highly interconnected microvessels in fibrin gel under defined medium conditions and the ability to align them using two methods, both of which involved anchoring the gel at both ends to constrain the cell-induced compaction. The first method used only defined medium and resulted in moderate alignment. The second method used defined and serum-containing media sequentially to achieve high levels of microvessel alignment.

Building an inpatient addiction medicine consult service in Sudbury, Canada: preliminary data and lessons learned in the era of COVID-19.

OBJECTIVE: The goal of this study was to (1) Describe the patient population of a newly implemented addiction medicine consult service (AMCS); (2) Evaluate referrals to community-based addiction support services and acute health service use, over time; (3) Provide lessons learned. METHODS: A retrospective observational analysis was conducted at Health Sciences North in Sudbury, Ontario, Canada, with a newly implemented AMCS from November 2018 and July 2021. Data were collected using the hospital's electronic medical records. The outcomes measured included the number of emergency department visits, inpatient admissions, and re-visits over time. An interrupted time-series analysis was performed to measure the effect of AMCS implementation on acute health service use at Health Sciences North. RESULTS: A total of 833 unique patients were assessed through the AMCS. A total of 1,294 referrals were made to community-based addiction support services, with the highest proportion of referrals between August and October 2020. The post-intervention trend for ED visits, ED re-visits, ED length of stay, inpatient visits, re-visits, and inpatient length of stay did not significantly differ from the pre-intervention period. CONCLUSION: Implementation of an AMCS provides a focused service for patients using with substance use disorders. The service resulted in a high referral rate to community-based addiction support services and limited changes in health service usage.

Association of prescribed oral stimulants on cocaine use among patients enrolled in opioid agonist treatment: A retrospective longitudinal cohort study.

Objectives: The objective of this study was to measure the association of prescribed oral stimulants with the consumption of cocaine among a population of patients receiving Opioid Agonist Therapy (OAT). Methods: The study was a retrospective clinical cohort study using the medical records of all patients receiving OAT who attended treatment clinics within the Canadian Addiction Treatment Centers (CATC) in Ontario from April 2014 to February 2021. Linear mixed-effects models were fit for the exposure of prescribed oral stimulants, and the outcome of a positive urinalysis drug screen for cocaine. Covariates for age, sex, and a random effect for patients were fitted to account for differences between and within patient observations over time. Results: Among patients receiving OAT therapy n = 314 patients were prescribed oral stimulants and n = 11,879 patients were not prescribed oral stimulants among Ontario CATC clinics (n = 92, n = 145 physicians), the mean age at enrollment for patients receiving oral stimulants was 37.0, SD = 8.8, with 43.6% female patients and for patients not receiving oral stimulants mean age was 36.6, SD = 10.7, with 39.6% female patients. Linear mixed effects models showed no difference in cocaine-positive urine tests over time for fixed effects B = 0.001, however, when considering the Interclass correlation coefficient (ICC) between the fixed effects, we found that time since the prescription of an oral stimulant was associated with a decrease of ICC = -0.14 in cocaine positive urine tests. Increasing age at prescription ICC = -0.92, and being male ICC = -0.23 were associated with decreasing cocaine-positive urine. Conclusion: The use of oral stimulant prescriptions to treat cocaine use had no clinically significant benefit in a real-world setting. Patients who receive prescriptions for oral stimulants consume more cocaine before and after treatment compared to patients without an oral stimulant prescription. We also observed that cocaine use was reduced with increased time since treatment initiation.

Evaluating the association between urine drug screening frequency and retention in opioid agonist treatment in Ontario, Canada: a retrospective cohort study.

OBJECTIVE: The objective of this study was to evaluate how urine drug screening (UDS) frequency is associated with retention in opioid agonist treatment (OAT). METHODS: Data for this retrospective cohort study of 55 921 adults in OAT in Ontario, Canada, were derived from administrative sources between 1 January 2011 and 31 December 2015. All patient information was linked anonymously across databases using encrypted health card numbers. Descriptive statistics were calculated for comparing UDS frequency groups using standardised differences (d) where d less than 10% indicated a statistically significant difference. A logistic regression model was then used to calculate ORs adjusting for baseline covariates, including sex, age, location of residence, income quintile, mental disorders, HIV status and deep tissue infections. RESULTS: Over 70% of the cohort had four or more UDS tests per month (weekly or more UDS). Significant associations were observed between UDS frequency and 1-year treatment retention in OAT biweekly (adjusted OR (aOR)=3.20, 95% CI 2.75 to 3.75); weekly UDS (aOR=6.86, 95% CI 5.88 to 8.00) and more than weekly (aOR=8.03, 95% CI 6.87 to 9.38) using the monthly or less groups as the reference. CONCLUSION: This study identified an association between weekly UDS and 1-year treatment retention in OAT. There is an active discussion within Canada about the utility of UDS. The lack of evidence for the impact of UDS on retention has left it open to some to argue they simply provide a barrier to patient engagement. Therefore, it is timely of this study to demonstrate that more frequent urine testing is not associated with a reduction in treatment retention.

Negative Impact of Amphetamine-Type Stimulant Use on Opioid Agonist Treatment Retention in Ontario, Canada.

Objective: The objective of this study was to evaluate epidemiological trends of co-use patterns of amphetamine-type stimulants and opioids and the impact of co-use patterns on Opioid Agonist Treatment (OAT) retention in Ontario, Canada. The secondary objective was to assess geographical variation in amphetamine-type stimulant use in Northern Rural, Northern Urban, Southern Rural and Southern Urban Areas of Ontario. Methods: A retrospective cohort study on 32,674 adults receiving OAT from ~70 clinics was conducted between January 1, 2014, and December 31, 2020, in Ontario, Canada. Patients were divided into four groups base on the proportion of positive urine drug screening results for amphetamine-type stimulants during treatment: group 1 (0-25%), group 2 (25-50%), group 3 (50-75%), and groups 4 (75-100%). A Fractional logistic regression model was used to evaluate differences over time in amphetamine-type stimulant use with urine drug screening results. A Cox Proportional Hazard Ratio model was used to calculate the impact of amphetamine-type stimulant use on retention in OAT and adjusted for sociodemographic characteristics, drug use and clinical factors. Lastly, a logistic regression model was used on a subgroup of patients to assess the impact of geography on amphetamine-type stimulant use in Northern Rural, Northern Urban, Southern Rural and Southern Urban Areas of Ontario. Results: There were significant differences in amphetamine-type stimulant positive urine drug screening results year-over-year from 2015 to 2020. Significant differences were observed between amphetamine-type stimulant groups with regards to sociodemographic, clinical and drug use factors. Compared to those with no amphetamine-type stimulant use, the number of days retained in OAT treatment for amphetamine-type stimulant users was reduced (hazard ratio 1.19; 95% confidence interval = 1.07-1.17; p < 0.001). Lastly, an adjusted logistic regression model showed a significant increase in the likelihood of amphetamine-type stimulant use in Northern Rural regions compared to Southern Urban areas. Conclusion: There was a significant increase in amphetamine-type stimulant use among individuals in OAT from 2014 to 2020, associated with decreased OAT retention. Research is required to determine if tailored strategies specific to individuals in OAT who use amphetamine-type stimulants can improve OAT outcomes.

Evidence of increased Fentanyl use during the COVID-19 pandemic among opioid agonist treatment patients in Ontario, Canada.

BACKGROUND: Amid the opioid crisis, the health care system is restructuring to prevent and treat COVID-19. Individuals in opioid agonist treatment (OAT) are uniquely challenged because of disruption to treatment, medication diversion, and isolation during the pandemic. METHODS: Between January and September 2020, we utilized the electronic medical record from a chain of 67 opioid agonist treatment clinics in Ontario, Canada, to examine routinely collected urine drug screen results of patients in opioid agonist treatment by Public Health Units. RESULTS: We present evidence of a 108% increase in the percentage of fentanyl positive urine drug screens from April to September (p< 0.001). During the same period, health regions in northern and southwestern Ontario, areas with a high concentration of rural communities, have seen the most notable increase in the percent of fentanyl positive urine drug screen results. CONCLUSION: The use of fentanyl increased by 108% among OAT patients in Ontario during the COVID 19 pandemic. We argue that the persistent increase of fentanyl exposure over time, specifically in the OAT population, suggests that reduced monitoring may decrease OAT's effectiveness and negatively impact patient outcomes.

Evidence of Increased Age and Sex Standardized Death Rates Among Individuals Who Accessed Opioid Agonist Treatment Before the Era of Synthetic Opioids in Ontario, Canada.

Objective The objective of this study was to evaluate age-sex standardized death rates (ASDR) from all causes from 2011 to 2015 among people who have accessed opioid agonist treatment (OAT) and compare rates living in the Northern and Southern areas of Ontario. Methods Routinely collected administrative health data was used to calculate crude death rates and age-sex standardized death rates (ASDRs) per 1,000,000 population of individuals who accessed OAT and compared the rates geographically from 2011 to 2015. The weighted ASDRs for each year were calculated by using the mid-year population of these regions. The rate ratios were calculated considering the base year as 2011.  Results A total of 55,924 adults who accessed OAT were included between January 1, 2011, and December 31, 2015. The majority of patients in the cohort - 52.3% - were between 15 and 34 years old, 32.5% were female, 11.3% were in the lowest income group, 71.1% lived in Southern areas. Overall, the ASDR steadily increased during the study period and spiked in 2015. We found that among individuals who had accessed OAT, living in Southern Ontario was associated with a lower risk of all-cause mortality than those living in Northern Ontario. ASDR for Northern Ontario was 20.0 (95% confidence interval (CI)= 10.2-34.2) in 2011, and 103.5(95%CI=78.5-133.5) in 2015, which was a five-fold increase from 2011. Whereas in Southern Ontario, ASDR in 2011 was 13.8 (95% CI= 11.5-16.5), and in 2015 ASDR was 60.8 (95%CI=55.8-66.1), which was only a 4-fold increase from 2011 Conclusion Our findings demonstrate evidence of a steadily increasing ASDR among individuals who accessed OAT with higher rates in Northern areas of the province before the era of synthetic opioids in Ontario, Canada.

A retrospective cohort study evaluating correlates of deep tissue infections among patients enrolled in opioid agonist treatment using administrative data in Ontario, Canada.

OBJECTIVE: The objective of this study was to evaluate the relationship between individual characteristics and deep tissue infections in patients enrolled in opioid agonist treatment in Ontario, Canada. METHODS: A retrospective cohort study was conducted on patients in opioid agonist treatment between January 1, 2011, and December 31, 2015 in Ontario, Canada. Patients were identified using data from the Ontario Health Insurance Plan Database, and the Ontario Drug Benefit Plan Database. We identified other study variables including all-cause mortality using data from the Registered Persons Database. Encrypted patient identifiers were used to link across databases. Logistic regression models were used to measure potential correlates of deep tissue infections. RESULTS: An increase in the incidence of deep tissue infections was observed between 2011 and 2016 for patients on opioid agonist treatment. Additionally, age, sex, positive HIV diagnosis, and all-cause mortality was correlated with deep tissue infection in our study population. CONCLUSION: The study indicates factors that are associated with deep tissue infections in the opioid use disorder population and can be used to identify opportunities to reduce the incidence of new infections.