Australian and New Zealand journal of public health, Jan 28, 2017
Many variations of venue lockout and last-drink policies have been introduced in attempts to redu... more Many variations of venue lockout and last-drink policies have been introduced in attempts to reduce drinking-related harms. We estimate the public health gains and licensee costs of these policies using a computer simulated population of young adults engaging in heavy drinking. Using an agent-based model we implemented 1 am/2 am/3 am venue lockouts in conjunction with last drinks zero/one/two hours later, or at current closing times. Outcomes included: the number of incidents of verbal aggression in public drinking venues, private venues or on the street; and changed revenue to public venues. The most effective policy in reducing verbal aggression among agents was 1 am lockouts with current closing times. All policies produced substantial reductions in street-based incidents of verbal aggression among agents (33-81%) due to the smoothing of transport demand. Direct revenue losses were 1-9% for simulated licensees, with later lockout times and longer periods between lockout and last ...
Previous research into psychological distress among people who inject drugs (PWID) is predominant... more Previous research into psychological distress among people who inject drugs (PWID) is predominantly cross-sectional; we determined longitudinal predictors of change in psychological distress among a cohort of PWID. We examined Kessler Psychological Distress Scale (K10) scores from 564 PWID (66% male) enrolled in the Melbourne Injecting Drug User Cohort Study. Gender-stratified linear models with fixed effects for each participant were used to examine correlates of change in individual K10 scores. Further linear regressions of adjusted K10 scores were used to measure correlations between demographic variables. Participants reported higher K10 scores (higher psychological distress) than the general Australian population (mean K10 scores 23.4 (95%CI 22.6-24.2) and 14.5 (95%CI 14.3-14.7) respectively). The cohort's mean K10 score did not significantly differ over time, but individual variations were common. Women reported higher K10 scores than men (mean baseline K10 scores 25.2 (95%CI 23.9-26.6) and 22.4 (95%CI 21.5-23.3) respectively), however no significant differences remained after controlling for temporal factors. Key predictors of increases in K10 scores were being the victim of an assault in the past six months (P<0.001 for women and men) and intentionally overdosing in the past 12 months (P=.010 for women and P<0.001 for men). PWID experience higher levels of psychological distress than the general population. Temporal rather than individual factors may account for the higher levels of psychological distress reported among women. Interventions to reduce rates of assault and/or intentional overdose should be explored to reduce high levels of psychological distress among PWID.
Australian and New Zealand journal of public health, Jan 14, 2016
To determine what percentage of Victorians with a history of notified hepatitis C exposure receiv... more To determine what percentage of Victorians with a history of notified hepatitis C exposure received appropriate follow-up diagnostic services between 2001 and 2012. Individual notification data and aggregate Medicare and supplementary testing data were entered into a compartmental transition model, which was used to estimate the percentage of people with a hepatitis C notification who were yet to receive either a negative diagnostic test for viral nucleic acid, or a test for viral genotype, at the end of 2012. We estimate that 58.2% (uncertainty interval: 42.2%, 72.4%) of Victorians with a hepatitis C notification between 2001 and 2012 did not receive either a negative test for viral nucleic acid or a viral genotyping test during the study period. At the end of 2012, we estimate there were approximately 20,400 Victorians living with hepatitis C antibodies who were yet to receive testing, of which approximately 9,300 would have been aged 45 years or older. A majority of people living...
Coverage is used as one indicator of needle and syringe program (NSP) effectiveness. At the indiv... more Coverage is used as one indicator of needle and syringe program (NSP) effectiveness. At the individual level, coverage is typically defined as an estimate of the proportion of a person who injects drugs' (PWID) injecting episodes that utilise a sterile syringe. In this paper, we explore levels of individual syringe coverage and its changes over time. Data were extracted from 1889 interviews involving 502 participants drawn from the Melbourne drug user cohort study (MIX). We asked questions relating to participants syringe acquisition, distribution and injecting frequency within the two weeks before interview. We created a dichotomous coverage variable that classified participants as sufficiently (≥100 %) covered if all their injecting episodes utilised at least one sterile syringe, and insufficiently (<100 %) covered if not. We categorised participants as "consistently covered" if they were sufficiently covered across interviews; as "consistently uncovered"...
The Eynard-Orantin invariants of a plane curve are multilinear differentials on the curve. For a ... more The Eynard-Orantin invariants of a plane curve are multilinear differentials on the curve. For a particular class of genus zero plane curves these invariants can be equivalently expressed in terms of simpler expressions given by polynomials obtained from an expansion of the Eynard-Orantin invariants around a point on the curve. This class of curves contains many interesting examples.
The advent of highly effective hepatitis C (HCV) treatments has questioned the need for a vaccine... more The advent of highly effective hepatitis C (HCV) treatments has questioned the need for a vaccine to control HCV amongst people who inject drugs (PWID). However, high treatment costs and ongoing reinfection risk suggest it could still play a role. We compared the impact of HCV vaccination amongst PWID against providing HCV treatment. Dynamic HCV vaccination and treatment models among PWID were used to determine the vaccination and treatment rates required to reduce chronic HCV prevalence or incidence in the UK over 20 or 40 years. Projections considered a low (50% protection for 5 years), moderate (70% protection for 10 years) or high (90% protection for 20 years) efficacy vaccine. Sensitivities to various parameters were examined. To halve chronic HCV prevalence over 40 years, the low, moderate and high efficacy vaccines required annual vaccination rates (coverage after 20 years) of 162 (72%), 77 (56%) and 44 (38%) per 1000 PWID, respectively. These vaccination rates were 16, 7.6 and 4.4 times greater than corresponding treatment rates. To halve prevalence over 20 years nearly doubled these vaccination rates (moderate and high efficacy vaccines only) and the vaccination-to-treatment ratio increased by 20%. For all scenarios considered, required annual vaccination rates and vaccination-to-treatment ratios were at least a third lower to reduce incidence than prevalence. Baseline HCV prevalence had little effect on the vaccine&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s impact on prevalence or incidence, but substantially affected the vaccination-to-treatment ratios. Behavioural risk heterogeneity only had an effect if we assumed no transitions between high and low risk states and vaccinations were targeted or if PWID were high risk for their first year. Achievable coverage levels of a low efficacy prophylactic HCV vaccine could greatly reduce HCV transmission amongst PWID. Current high treatment costs ensure vaccination could still be an important intervention option.
The WHO&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;a... more The WHO&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s draft HCV elimination targets propose an 80% reduction in incidence and a 65% reduction in HCV-related deaths by 2030. We estimate the treatment scale-up required and cost-effectiveness of reaching these targets among injecting drug use (IDU)-acquired infections using Australian disease estimates. A mathematical model of HCV transmission, liver disease progression and treatment among current and former people who inject drugs (PWID). Treatment scale-up and the most efficient allocation to priority groups (PWID or patients with advanced liver disease) were determined; total healthcare and treatment costs, quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs) compared with inaction were calculated. 5662 (95% CI 5202 to 6901) courses per year (30/1000 IDU-acquired infections) were required, prioritised to patients with advanced liver disease, to reach the mortality target. 4725 (3278-8420) courses per year (59/1000 PWID) were required, prioritised to PWID, to reach the incidence target; this also achieved the mortality target, but to avoid clinically unacceptable HCV-related deaths an additional 5564 (1959-6917) treatments per year (30/1000 IDU-acquired infections) were required for 5 years for patients with advanced liver disease. Achieving both targets in this way cost $A4.6 ($A4.2-$A4.9) billion more than inaction, but gained 184 000 (119 000-417 000) QALYs, giving an ICER of $A25 121 ($A11 062-$A39 036) per QALY gained. Achieving WHO elimination targets with treatment scale-up is likely to be cost-effective, based on Australian HCV burden and demographics. Reducing incidence should be a priority to achieve both WHO elimination goals in the long-term.
The International journal on drug policy, Jun 27, 2016
The late-night accessibility of entertainment precincts is a contributing factor to acute drinkin... more The late-night accessibility of entertainment precincts is a contributing factor to acute drinking-related harms. Using computer simulation we test the effects of improved public transport (PT) and venue lockouts on verbal aggression, consumption-related harms and transport-related harms among a population of young adults engaging in heavy drinking in Melbourne. Using an agent-based model we implemented: a two-hour PT extension/24-hour PT; 1am/3am venue lockouts; and combinations of both. Outcomes determined for outer-urban (OU) and inner-city (IC) residents were: the number of incidents of verbal aggression inside public and private venues; the number of people ejected from public venues for being intoxicated; and the percentage of people experiencing verbal aggression, consumption-related harms and transport-related harms. All-night PT reduced verbal aggression in the model by 21% but displaced some incidents among OU residents from private to public settings. Comparatively, 1am l...
The discovery of highly effective hepatitis C virus (HCV) treatments has led to discussion of eli... more The discovery of highly effective hepatitis C virus (HCV) treatments has led to discussion of elimination and intensified interest in models of HCV transmission. In developed settings, HCV disproportionally affects people who inject drugs (PWID), and models are typically used to provide an evidence base for the effectiveness of interventions such as needle and syringe programs, opioid substitution therapy and more recently treating PWID with new generation therapies to achieve specified reductions in prevalence and / or incidence. This manuscript reviews deterministic compartmental S-I, deterministic compartmental S-I-S and network-based transmission models of HCV among PWID. We detail typical assumptions made when modeling injecting risk behavior, virus transmission, treatment and re-infection and how they correspond with available evidence and empirical data.
To determine the effects of 1) a condom distribution program and 2) a condom distribution program... more To determine the effects of 1) a condom distribution program and 2) a condom distribution program combined with opt-out sexually transmitted infection (STI) screening on the transmission and prevalence of STIs in a prison system. Using data from an implementation evaluation of a state-wide prison condom program and parameter estimates from available literature, a deterministic model was developed to quantify the incidence and prevalence of sexually transmitted HIV, hepatitis B, chlamydia, syphilis and gonorrhoea across 14 Victorian prisons. The model included individual prison populations (by longer (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;2 years) or shorter sentence lengths) and monthly prisoner transfers. For each STI, simulations were compared: without any intervention; with a condom distribution program; and with a combined condom and opt-out STI screening at prison reception intervention program. Condoms reduced the annual incidence of syphilis by 99% (N = 66 averted cases); gonorrhoea by 98% (N = 113 cases); hepatitis B by 71% (N = 5 cases); chlamydia by 27% (N = 196 cases); and HIV by 50% (N = 2 cases every 10 years). Condom availability changed the in-prison epidemiology of gonorrhoea and syphilis from self-sustaining to levels unlikely to result in infection outbreaks; however, condoms did not reduce chlamydia prevalence below a self-sustaining level due to its high infectiousness, high prevalence and low detection rate. When combined with a screening intervention program, condoms reduced chlamydia prevalence further, but not below a self-sustaining level. The low prevalence of HIV and hepatitis B in Australian prisons meant the effects of condoms were predicted to be small. Condoms are predicted to effectively reduce the incidence of STIs in prison and are predicted to control syphilis and gonorrhoea transmission, however even combined with a screening on arrival program may be insufficient to reduce chlamydia prevalence below self-sustaining levels. To control chlamydia transmission additional screening of the existing prison population would be required.
Journal of gastroenterology and hepatology, Jan 30, 2015
Reducing the burden of hepatitis C virus (HCV) related liver disease will require treating people... more Reducing the burden of hepatitis C virus (HCV) related liver disease will require treating people who inject drugs (PWID), the group at most risk of infection and transmission. We determine the cost-effectiveness of treating PWID with interferon-free direct-acting antiviral therapy in Australia. Using a deterministic model of HCV treatment and liver disease progression, including a fixed rate of re-infection, the expected healthcare costs and quality-adjusted life years (QALYs) of a cohort of newly HCV-infected PWID were calculated for: no treatment; treatment after initial infection ('early-treatment'); and treatment prior to developing compensated cirrhosis ('late-treatment'). Incremental cost-effectiveness ratios (ICERs) were used to compare scenarios. Late-treatment was cost-effective compared to no treatment, with a discounted average gain of 2.98 (95%CI 2.88-5.22) QALYs for an additional cost of $15,132 ($11,246-18,922), giving an ICER of $5,078 ($2,847-5,295) ...
Hepatitis C virus (HCV) elimination is being seriously considered globally. Current elimination m... more Hepatitis C virus (HCV) elimination is being seriously considered globally. Current elimination models require a combination of highly effective HCV treatment and harm reduction, but high treatment costs make such strategies prohibitively expensive. Vaccines should play a key role in elimination but their best use alongside treatments is unclear. For three vaccines with different efficacies we used a mathematical model to estimate the additional reduction in HCV prevalence when vaccinating after treatment; and to identify in which settings vaccines could most effectively reduce the number of treatments required to achieve fixed reductions in HCV prevalence among people who inject drugs (PWID). A deterministic model of HCV transmission among PWID was calibrated for settings with 25, 50 and 75% chronic HCV prevalence among PWID, stratified by high-risk or low-risk PWID. For vaccines with 30, 60 or 90% efficacies, different rates of treatment and vaccination were introduced. We compare...
: Twenty-four otherwise healthy patients scheduled for elective major abdominal surgery received ... more : Twenty-four otherwise healthy patients scheduled for elective major abdominal surgery received general anesthesia plus lumbar epidural analgesia with a loading dose of plain bupivacaine 0.5% to produce sensory analgesia (pinprick) from Th4 to S5. Two groups of patients were matched with regard to age, sex, height, body weight, and surgical procedure. The 12 patients in one group received continuous infusion of plain bupivacaine 0.5%, 8 ml/h, and the other group of 12 patients received plain bupivacaine 0.25%, 16 ml/h, starting 30 minutes after a loading dose of bupivacaine 0.5%, 23.0 +/- 0.5 ml. Pain scores on a 5-point scale and sensory analgesia (pinprick) were assessed hourly for 16 hours after skin incision. If sensory analgesia decreased more than 5 segments from the preoperative level or if the pain score reached 2 (moderate pain), the patients were removed from the study, and pain was treated with opiates. Preoperative mean (+/-SEM) sensory levels of analgesia were similar ...
ABSTRACT Background: Understanding of substitution patterns in drug using careers is limited. Bet... more ABSTRACT Background: Understanding of substitution patterns in drug using careers is limited. Between 2009 and mid-2013, the purity-adjusted price of methamphetamine declined sharply in Melbourne in absolute terms and relative to the purity-adjusted price of heroin. We determine whether there were associated increases among people who inject drugs (PWID) in (1) use of methamphetamine and (2) citing methamphetamine as the drug of choice. Method: Responses to “drug of choice” and “most used drug” were obtained from baseline and follow-up interviews of the 688 PWID enrolled in the Melbourne Injecting Drug User Cohort Study between April 2008 and August 2013, categorised as heroin, methamphetamine, cannabis or other. Previous month heroin and methamphetamine use was reported at baseline by 82% and 41% of participants, respectively, and 51% had completed four or more interviews in this period. A Markov model that included marginal effects for methamphetamine purity-adjusted price was used to calculate (1) transitions between drug of choice and (2) conditional probabilities for most used drug. Parameters were determined by fitting multinomial logistic models to appropriate data subsets. Results: At baseline, the majority of participants reported heroin as both their preferred drug and the drug they used most. There were no significant increases in reports of methamphetamine as drug of choice, or as the most used drug. Conclusion: In a cohort of PWID who reported a range of drug behaviours, there was little evidence of drug substitution into methamphetamine, despite substantial declines in its purity-adjusted price.
Australian and New Zealand journal of public health, Jan 28, 2017
Many variations of venue lockout and last-drink policies have been introduced in attempts to redu... more Many variations of venue lockout and last-drink policies have been introduced in attempts to reduce drinking-related harms. We estimate the public health gains and licensee costs of these policies using a computer simulated population of young adults engaging in heavy drinking. Using an agent-based model we implemented 1 am/2 am/3 am venue lockouts in conjunction with last drinks zero/one/two hours later, or at current closing times. Outcomes included: the number of incidents of verbal aggression in public drinking venues, private venues or on the street; and changed revenue to public venues. The most effective policy in reducing verbal aggression among agents was 1 am lockouts with current closing times. All policies produced substantial reductions in street-based incidents of verbal aggression among agents (33-81%) due to the smoothing of transport demand. Direct revenue losses were 1-9% for simulated licensees, with later lockout times and longer periods between lockout and last ...
Previous research into psychological distress among people who inject drugs (PWID) is predominant... more Previous research into psychological distress among people who inject drugs (PWID) is predominantly cross-sectional; we determined longitudinal predictors of change in psychological distress among a cohort of PWID. We examined Kessler Psychological Distress Scale (K10) scores from 564 PWID (66% male) enrolled in the Melbourne Injecting Drug User Cohort Study. Gender-stratified linear models with fixed effects for each participant were used to examine correlates of change in individual K10 scores. Further linear regressions of adjusted K10 scores were used to measure correlations between demographic variables. Participants reported higher K10 scores (higher psychological distress) than the general Australian population (mean K10 scores 23.4 (95%CI 22.6-24.2) and 14.5 (95%CI 14.3-14.7) respectively). The cohort&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s mean K10 score did not significantly differ over time, but individual variations were common. Women reported higher K10 scores than men (mean baseline K10 scores 25.2 (95%CI 23.9-26.6) and 22.4 (95%CI 21.5-23.3) respectively), however no significant differences remained after controlling for temporal factors. Key predictors of increases in K10 scores were being the victim of an assault in the past six months (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001 for women and men) and intentionally overdosing in the past 12 months (P=.010 for women and P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001 for men). PWID experience higher levels of psychological distress than the general population. Temporal rather than individual factors may account for the higher levels of psychological distress reported among women. Interventions to reduce rates of assault and/or intentional overdose should be explored to reduce high levels of psychological distress among PWID.
Australian and New Zealand journal of public health, Jan 14, 2016
To determine what percentage of Victorians with a history of notified hepatitis C exposure receiv... more To determine what percentage of Victorians with a history of notified hepatitis C exposure received appropriate follow-up diagnostic services between 2001 and 2012. Individual notification data and aggregate Medicare and supplementary testing data were entered into a compartmental transition model, which was used to estimate the percentage of people with a hepatitis C notification who were yet to receive either a negative diagnostic test for viral nucleic acid, or a test for viral genotype, at the end of 2012. We estimate that 58.2% (uncertainty interval: 42.2%, 72.4%) of Victorians with a hepatitis C notification between 2001 and 2012 did not receive either a negative test for viral nucleic acid or a viral genotyping test during the study period. At the end of 2012, we estimate there were approximately 20,400 Victorians living with hepatitis C antibodies who were yet to receive testing, of which approximately 9,300 would have been aged 45 years or older. A majority of people living...
Coverage is used as one indicator of needle and syringe program (NSP) effectiveness. At the indiv... more Coverage is used as one indicator of needle and syringe program (NSP) effectiveness. At the individual level, coverage is typically defined as an estimate of the proportion of a person who injects drugs' (PWID) injecting episodes that utilise a sterile syringe. In this paper, we explore levels of individual syringe coverage and its changes over time. Data were extracted from 1889 interviews involving 502 participants drawn from the Melbourne drug user cohort study (MIX). We asked questions relating to participants syringe acquisition, distribution and injecting frequency within the two weeks before interview. We created a dichotomous coverage variable that classified participants as sufficiently (≥100 %) covered if all their injecting episodes utilised at least one sterile syringe, and insufficiently (<100 %) covered if not. We categorised participants as "consistently covered" if they were sufficiently covered across interviews; as "consistently uncovered"...
The Eynard-Orantin invariants of a plane curve are multilinear differentials on the curve. For a ... more The Eynard-Orantin invariants of a plane curve are multilinear differentials on the curve. For a particular class of genus zero plane curves these invariants can be equivalently expressed in terms of simpler expressions given by polynomials obtained from an expansion of the Eynard-Orantin invariants around a point on the curve. This class of curves contains many interesting examples.
The advent of highly effective hepatitis C (HCV) treatments has questioned the need for a vaccine... more The advent of highly effective hepatitis C (HCV) treatments has questioned the need for a vaccine to control HCV amongst people who inject drugs (PWID). However, high treatment costs and ongoing reinfection risk suggest it could still play a role. We compared the impact of HCV vaccination amongst PWID against providing HCV treatment. Dynamic HCV vaccination and treatment models among PWID were used to determine the vaccination and treatment rates required to reduce chronic HCV prevalence or incidence in the UK over 20 or 40 years. Projections considered a low (50% protection for 5 years), moderate (70% protection for 10 years) or high (90% protection for 20 years) efficacy vaccine. Sensitivities to various parameters were examined. To halve chronic HCV prevalence over 40 years, the low, moderate and high efficacy vaccines required annual vaccination rates (coverage after 20 years) of 162 (72%), 77 (56%) and 44 (38%) per 1000 PWID, respectively. These vaccination rates were 16, 7.6 and 4.4 times greater than corresponding treatment rates. To halve prevalence over 20 years nearly doubled these vaccination rates (moderate and high efficacy vaccines only) and the vaccination-to-treatment ratio increased by 20%. For all scenarios considered, required annual vaccination rates and vaccination-to-treatment ratios were at least a third lower to reduce incidence than prevalence. Baseline HCV prevalence had little effect on the vaccine&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s impact on prevalence or incidence, but substantially affected the vaccination-to-treatment ratios. Behavioural risk heterogeneity only had an effect if we assumed no transitions between high and low risk states and vaccinations were targeted or if PWID were high risk for their first year. Achievable coverage levels of a low efficacy prophylactic HCV vaccine could greatly reduce HCV transmission amongst PWID. Current high treatment costs ensure vaccination could still be an important intervention option.
The WHO&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;a... more The WHO&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s draft HCV elimination targets propose an 80% reduction in incidence and a 65% reduction in HCV-related deaths by 2030. We estimate the treatment scale-up required and cost-effectiveness of reaching these targets among injecting drug use (IDU)-acquired infections using Australian disease estimates. A mathematical model of HCV transmission, liver disease progression and treatment among current and former people who inject drugs (PWID). Treatment scale-up and the most efficient allocation to priority groups (PWID or patients with advanced liver disease) were determined; total healthcare and treatment costs, quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs) compared with inaction were calculated. 5662 (95% CI 5202 to 6901) courses per year (30/1000 IDU-acquired infections) were required, prioritised to patients with advanced liver disease, to reach the mortality target. 4725 (3278-8420) courses per year (59/1000 PWID) were required, prioritised to PWID, to reach the incidence target; this also achieved the mortality target, but to avoid clinically unacceptable HCV-related deaths an additional 5564 (1959-6917) treatments per year (30/1000 IDU-acquired infections) were required for 5 years for patients with advanced liver disease. Achieving both targets in this way cost $A4.6 ($A4.2-$A4.9) billion more than inaction, but gained 184 000 (119 000-417 000) QALYs, giving an ICER of $A25 121 ($A11 062-$A39 036) per QALY gained. Achieving WHO elimination targets with treatment scale-up is likely to be cost-effective, based on Australian HCV burden and demographics. Reducing incidence should be a priority to achieve both WHO elimination goals in the long-term.
The International journal on drug policy, Jun 27, 2016
The late-night accessibility of entertainment precincts is a contributing factor to acute drinkin... more The late-night accessibility of entertainment precincts is a contributing factor to acute drinking-related harms. Using computer simulation we test the effects of improved public transport (PT) and venue lockouts on verbal aggression, consumption-related harms and transport-related harms among a population of young adults engaging in heavy drinking in Melbourne. Using an agent-based model we implemented: a two-hour PT extension/24-hour PT; 1am/3am venue lockouts; and combinations of both. Outcomes determined for outer-urban (OU) and inner-city (IC) residents were: the number of incidents of verbal aggression inside public and private venues; the number of people ejected from public venues for being intoxicated; and the percentage of people experiencing verbal aggression, consumption-related harms and transport-related harms. All-night PT reduced verbal aggression in the model by 21% but displaced some incidents among OU residents from private to public settings. Comparatively, 1am l...
The discovery of highly effective hepatitis C virus (HCV) treatments has led to discussion of eli... more The discovery of highly effective hepatitis C virus (HCV) treatments has led to discussion of elimination and intensified interest in models of HCV transmission. In developed settings, HCV disproportionally affects people who inject drugs (PWID), and models are typically used to provide an evidence base for the effectiveness of interventions such as needle and syringe programs, opioid substitution therapy and more recently treating PWID with new generation therapies to achieve specified reductions in prevalence and / or incidence. This manuscript reviews deterministic compartmental S-I, deterministic compartmental S-I-S and network-based transmission models of HCV among PWID. We detail typical assumptions made when modeling injecting risk behavior, virus transmission, treatment and re-infection and how they correspond with available evidence and empirical data.
To determine the effects of 1) a condom distribution program and 2) a condom distribution program... more To determine the effects of 1) a condom distribution program and 2) a condom distribution program combined with opt-out sexually transmitted infection (STI) screening on the transmission and prevalence of STIs in a prison system. Using data from an implementation evaluation of a state-wide prison condom program and parameter estimates from available literature, a deterministic model was developed to quantify the incidence and prevalence of sexually transmitted HIV, hepatitis B, chlamydia, syphilis and gonorrhoea across 14 Victorian prisons. The model included individual prison populations (by longer (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;2 years) or shorter sentence lengths) and monthly prisoner transfers. For each STI, simulations were compared: without any intervention; with a condom distribution program; and with a combined condom and opt-out STI screening at prison reception intervention program. Condoms reduced the annual incidence of syphilis by 99% (N = 66 averted cases); gonorrhoea by 98% (N = 113 cases); hepatitis B by 71% (N = 5 cases); chlamydia by 27% (N = 196 cases); and HIV by 50% (N = 2 cases every 10 years). Condom availability changed the in-prison epidemiology of gonorrhoea and syphilis from self-sustaining to levels unlikely to result in infection outbreaks; however, condoms did not reduce chlamydia prevalence below a self-sustaining level due to its high infectiousness, high prevalence and low detection rate. When combined with a screening intervention program, condoms reduced chlamydia prevalence further, but not below a self-sustaining level. The low prevalence of HIV and hepatitis B in Australian prisons meant the effects of condoms were predicted to be small. Condoms are predicted to effectively reduce the incidence of STIs in prison and are predicted to control syphilis and gonorrhoea transmission, however even combined with a screening on arrival program may be insufficient to reduce chlamydia prevalence below self-sustaining levels. To control chlamydia transmission additional screening of the existing prison population would be required.
Journal of gastroenterology and hepatology, Jan 30, 2015
Reducing the burden of hepatitis C virus (HCV) related liver disease will require treating people... more Reducing the burden of hepatitis C virus (HCV) related liver disease will require treating people who inject drugs (PWID), the group at most risk of infection and transmission. We determine the cost-effectiveness of treating PWID with interferon-free direct-acting antiviral therapy in Australia. Using a deterministic model of HCV treatment and liver disease progression, including a fixed rate of re-infection, the expected healthcare costs and quality-adjusted life years (QALYs) of a cohort of newly HCV-infected PWID were calculated for: no treatment; treatment after initial infection ('early-treatment'); and treatment prior to developing compensated cirrhosis ('late-treatment'). Incremental cost-effectiveness ratios (ICERs) were used to compare scenarios. Late-treatment was cost-effective compared to no treatment, with a discounted average gain of 2.98 (95%CI 2.88-5.22) QALYs for an additional cost of $15,132 ($11,246-18,922), giving an ICER of $5,078 ($2,847-5,295) ...
Hepatitis C virus (HCV) elimination is being seriously considered globally. Current elimination m... more Hepatitis C virus (HCV) elimination is being seriously considered globally. Current elimination models require a combination of highly effective HCV treatment and harm reduction, but high treatment costs make such strategies prohibitively expensive. Vaccines should play a key role in elimination but their best use alongside treatments is unclear. For three vaccines with different efficacies we used a mathematical model to estimate the additional reduction in HCV prevalence when vaccinating after treatment; and to identify in which settings vaccines could most effectively reduce the number of treatments required to achieve fixed reductions in HCV prevalence among people who inject drugs (PWID). A deterministic model of HCV transmission among PWID was calibrated for settings with 25, 50 and 75% chronic HCV prevalence among PWID, stratified by high-risk or low-risk PWID. For vaccines with 30, 60 or 90% efficacies, different rates of treatment and vaccination were introduced. We compare...
: Twenty-four otherwise healthy patients scheduled for elective major abdominal surgery received ... more : Twenty-four otherwise healthy patients scheduled for elective major abdominal surgery received general anesthesia plus lumbar epidural analgesia with a loading dose of plain bupivacaine 0.5% to produce sensory analgesia (pinprick) from Th4 to S5. Two groups of patients were matched with regard to age, sex, height, body weight, and surgical procedure. The 12 patients in one group received continuous infusion of plain bupivacaine 0.5%, 8 ml/h, and the other group of 12 patients received plain bupivacaine 0.25%, 16 ml/h, starting 30 minutes after a loading dose of bupivacaine 0.5%, 23.0 +/- 0.5 ml. Pain scores on a 5-point scale and sensory analgesia (pinprick) were assessed hourly for 16 hours after skin incision. If sensory analgesia decreased more than 5 segments from the preoperative level or if the pain score reached 2 (moderate pain), the patients were removed from the study, and pain was treated with opiates. Preoperative mean (+/-SEM) sensory levels of analgesia were similar ...
ABSTRACT Background: Understanding of substitution patterns in drug using careers is limited. Bet... more ABSTRACT Background: Understanding of substitution patterns in drug using careers is limited. Between 2009 and mid-2013, the purity-adjusted price of methamphetamine declined sharply in Melbourne in absolute terms and relative to the purity-adjusted price of heroin. We determine whether there were associated increases among people who inject drugs (PWID) in (1) use of methamphetamine and (2) citing methamphetamine as the drug of choice. Method: Responses to “drug of choice” and “most used drug” were obtained from baseline and follow-up interviews of the 688 PWID enrolled in the Melbourne Injecting Drug User Cohort Study between April 2008 and August 2013, categorised as heroin, methamphetamine, cannabis or other. Previous month heroin and methamphetamine use was reported at baseline by 82% and 41% of participants, respectively, and 51% had completed four or more interviews in this period. A Markov model that included marginal effects for methamphetamine purity-adjusted price was used to calculate (1) transitions between drug of choice and (2) conditional probabilities for most used drug. Parameters were determined by fitting multinomial logistic models to appropriate data subsets. Results: At baseline, the majority of participants reported heroin as both their preferred drug and the drug they used most. There were no significant increases in reports of methamphetamine as drug of choice, or as the most used drug. Conclusion: In a cohort of PWID who reported a range of drug behaviours, there was little evidence of drug substitution into methamphetamine, despite substantial declines in its purity-adjusted price.
Uploads
Papers by Nick Scott