Medicine (St Vincent's) - Research Publications
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ItemPlatinum dissolution and tissue response following long-term electrical stimulation at high charge densities(IOP Publishing Ltd, 2021-04)Objective. Established guidelines for safe levels of electrical stimulation for neural prostheses are based on a limited range of the stimulus parameters used clinically. Recent studies have reported particulate platinum (Pt) associated with long-term clinical use of these devices, highlighting the need for more carefully defined safety limits. We previously reported no adverse effects of Pt corrosion products in the cochleae of guinea pigs following 4 weeks of electrical stimulation using charge densities far greater than the published safe limits for cochlear implants. The present study examines the histopathological effects of Pt within the cochlea following continuous stimulation at a charge density well above the defined safe limits for periods up to 6 months.Approach. Six cats were bilaterally implanted with Pt electrode arrays and unilaterally stimulated using charge balanced current pulses at a charge density of 267μC cm-2phase-1using a tripolar electrode configuration. Electrochemical measurements were made throughout the implant duration and evoked potentials recorded at the outset and on completion of the stimulation program. Cochleae were examined histologically for particulate Pt, tissue response, and auditory nerve survival; electrodes were examined for surface corrosion; and cochlea, brain, kidney, and liver tissue analysed for trace levels of Pt.Main results. Chronic stimulation resulted in both a significant increase in tissue response and particulate Pt within the tissue capsule surrounding the electrode array compared with implanted, unstimulated control cochleae. Importantly, there was no stimulus-induced loss of auditory neurons (ANs) or increase in evoked potential thresholds. Stimulated electrodes were significantly more corroded compared with unstimulated electrodes. Trace analysis revealed Pt in both stimulated and control cochleae although significantly greater levels were detected within stimulated cochleae. There was no evidence of Pt in brain or liver; however, trace levels of Pt were recorded in the kidneys of two animals. Finally, increased charge storage capacity and charge injection limit reflected the more extensive electrode corrosion associated with stimulated electrodes.Significance. Long-term electrical stimulation of Pt electrodes at a charge density well above existing safety limits and nearly an order of magnitude higher than levels used clinically, does not adversely affect the AN population or reduce neural function, despite a stimulus-induced tissue response and the accumulation of Pt corrosion product. The mechanism resulting in Pt within the unstimulated cochlea is unclear, while the level of Pt observed systemically following stimulation at these very high charge densities does not appear to be of clinical significance.
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ItemReal-world monitoring progress towards the elimination of hepatitis C virus in Australia using sentinel surveillance of primary care clinics; an ecological study of hepatitis C virus antibody tests from 2009 to 2019(CAMBRIDGE UNIV PRESS, 2021-12-06)To achieve the elimination of the hepatitis C virus (HCV), sustained and sufficient levels of HCV testing is critical. The purpose of this study was to assess trends in testing and evaluate the effectiveness of strategies to diagnose people living with HCV. Data were from 12 primary care clinics in Victoria, Australia, that provide targeted services to people who inject drugs (PWID), alongside general health care. This ecological study spanned 2009-2019 and included analyses of trends in annual numbers of HCV antibody tests among individuals with no previous positive HCV antibody test recorded and annual test yield (positive HCV antibody tests/all HCV antibody tests). Generalised linear models estimated the association between count outcomes (HCV antibody tests and positive HCV antibody tests) and time, and χ2 test assessed the trend in test yield. A total of 44 889 HCV antibody tests were conducted 2009-2019; test numbers increased 6% annually on average [95% confidence interval (CI) 4-9]. Test yield declined from 2009 (21%) to 2019 (9%) (χ2P = <0.01). In more recent years (2013-2019) annual test yield remained relatively stable. Modest increases in HCV antibody testing and stable but high test yield within clinics delivering services to PWID highlights testing strategies are resulting in people are being diagnosed however further increases in the testing of people at risk of HCV or living with HCV may be needed to reach Australia's HCV elimination goals.
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ItemMaternal thiopurine metabolism during pregnancy in inflammatory bowel disease and clearance of thiopurine metabolites and outcomes in exposed neonates(WILEY, 2021-04)BACKGROUND: Azathioprine and mercaptopurine are considered safe during pregnancy. However, the pharmacokinetic effects of pregnancy on thiopurine metabolism are undefined. AIMS: To characterise thiopurine metabolism in pregnancy and measure infant metabolite levels and outcomes. METHODS: Women with IBD who were taking a thiopurine and pregnant or trying to conceive were recruited. Maternal thiopurine metabolites were measured pre-conception, in each trimester, at delivery and post-partum. Infant metabolite levels, full blood examination and liver function testing were performed at birth, and repeated until levels undetectable and haematological and biochemical abnormalities resolved. RESULTS: Forty patients were included with measurements on at least two occasions, and two with only mother-baby levels at delivery. The median maternal 6-TGN level dropped in the second trimester compared with post-partum (179.0 vs 323.5 pmol/8 × 108 RBCs, P < 0.001) and the median 6-MMP level increased in the second trimester compared with post-partum (1103.0 vs 329.5 pmol/8 × 108 RBCs, P < 0.01). At delivery, the median 6-TGN level was lower in infants (n = 20) than mothers (78.5 vs 217 pmol/8 × 108 RBCs) (P < 0.001). Metabolites were not detected at 6 weeks in any infants. Anaemia was not seen, but thrombocytosis and abnormal liver biochemistry were detected in 80% of infants from 6 weeks, which gradually improved. CONCLUSIONS: 6-TGN levels decrease and 6-MMP levels increase in the second trimester of pregnancy. Infants are exposed to thiopurine metabolites at low levels with clearance by 6 weeks and no anaemia. The cause of infant thrombocytosis and abnormal liver biochemistry in the absence of metabolites is unclear.
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ItemQuantifying early gastric cancer in Australia: What is the opportunity for gastric endoscopic submucosal dissection?(Wiley, 2021-10)BACKGROUND AND AIMS: Endoscopic submucosal dissection (ESD) is the recommended treatment for early gastric cancer (EGC). However, there are challenges in attaining expertise in ESD in countries where the incidence of gastric cancer and proportion diagnosed at an early stage of disease are relatively low. This study aims to establish the proportion of gastric cancer meeting histological criteria for EGC, which may be suitable for ESD, in a Western population. METHODS: Gastric cancers reported to the Victorian Cancer Registry between January 2011 and December 2016 were analyzed. EGC was defined as tumor confined to mucosa (T1a) or submucosa (T1b). Histology reports were analyzed using Japanese and European guidelines to identify potential ESD candidates. Criteria for extended ESD were based on grade of differentiation, tumor depth, lymphovascular and perineural invasion, and ulceration. RESULTS: Twenty percent of 1217 gastric cancers was EGC (237 cases), with detailed histopathology reports suitable for evaluating ESD criteria recorded in 182 cases. Standard and extended ESD criteria were met in 46% (84/182) and 75% (132/182), respectively. Actual treatment of the 237 EGC was endoscopic in 14% (n = 33) and surgery in 86% (n = 204). Endoscopically treated EGCs were more likely to be stage T1a and located in the proximal stomach. CONCLUSIONS: EGCs represented 20% of reported gastric adenocarcinomas with the majority fulfilling criteria for ESD. ESD should be considered in the management algorithm and discussed at tumor board meetings involving interventional endoscopists. To increase utilization of ESD, systems need to be implemented to improve training, accreditation, and access to ESD.
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ItemAssessing the feasibility, acceptability and impacts of an education program on hepatitis B testing uptake among ethnic Chinese in Australia: results of a randomised controlled pilot study(BMC, 2021-10-15)BACKGROUND: In Australia, Chinese migrants are among the populations most affected by hepatitis B virus (HBV) infection but often experience late diagnosis or access to clinical care. This study aims to explore approaches to increase HBV testing in Australia's Chinese community and inform evaluation planning, specifically to i) assess the feasibility and acceptability of HBV educational programs, and ii) compare HBV testing uptake in people receiving a tailored education resource focussing on liver cancer prevention compared with a standard HBV education package. METHODS: This is a pre-post mixed-methods pilot and feasibility study. People of Chinese ethnicity and unsure of their HBV infection or immunity status were recruited from ten community sites in Melbourne, Australia in 2019-2020. Participants were randomised to receive an education package (comprised of a leaflet and in-person one-on-one educational session) with a focus on either 1) standard HBV-related information, or 2) liver cancer prevention. Participants completed a baseline questionnaire prior to receiving the intervention and were followed up at 6 months' time for a questionnaire and an opt-in semi-structured interview. Primary study outcomes included feasibility of study procedures, measured by recruitment, participation, and retention rates; acceptability of the education program assessed by acceptability scores; and HBV testing uptake rate in each arm. Secondary outcomes include HBV-related knowledge change, assessed by pre-post comparison; and factors affecting participants' testing behaviour analysed using qualitative data. RESULTS: Fifty-four participants received an education package; baseline and follow-up data from 33 (61%) were available. The study procedures of recruitment and retention were feasible; the acceptability of the education program was moderate with improved HBV-related knowledge observed. Four participants self-reported being tested: one (1/15, 7%) in the standard HBV information group and three (3/18, 17%) in the liver cancer prevention information group. Factors identified as affecting testing included perceived relevance and seriousness of HBV, healthcare access and costs of testing, and perceptions of the role of primary care providers in HBV-related care. CONCLUSION: A tailored education program targeting ethnic Chinese in Australia was feasible with moderate acceptability. A larger study is required to determine if a liver cancer prevention message would improve HBV testing uptake in Chinese community than standard HBV education message. Supports from healthcare providers, community-based testing programs, and public health education programs are likely needed to motivate diagnostic testing among Chinese people at risk of HBV infection.
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ItemSofosbuvir and daclatasvir therapy in patients with hepatitis C-related advanced decompensated liver disease (MELD ≥ 15)(WILEY, 2018-02)BACKGROUND: Antiviral therapy for hepatitis C has the potential to improve liver function in patients with decompensated cirrhosis. AIMS: To examine the virological response and effect of viral clearance in patients with decompensated hepatitis C cirrhosis all with MELD scores ≥15 following sofosbuvir/daclatasvir ± ribavirin. METHODS: We prospectively collected data on patients who commenced sofosbuvir/daclatasvir for 24-weeks under the Australian patient supply program (TOSCAR) and analysed outcomes including sustained viral response at 12 weeks (SVR12), death and transplant. RESULTS: 108 patients (M/F, 79/29; median age 56years; Child-Pugh 10; MELD 16; genotype 1/3, 55/47) received sofosbuvir/daclatasvir and two also received ribavirin. On intention-to-treat, the SVR12 rate was 70% (76/108). Seventy-eight patients completed 24-weeks therapy. SVR12 was achieved in 56 of these patients on per-protocol-analysis (76%). SVR12 was 80% in genotype 1 compared to 69% in genotype 3. Thirty patients failed to complete therapy. In patients achieving SVR12, median MELD and Child-Pugh fell from 16(IQR15-17) to 14(12-17) and 10(9-11) to 8(7-9), respectively (P<.001). In those who died, MELD increased from 16 to 23 at death (P=.036). Patients who required transplantation had a significantly higher baseline MELD (20) compared to those patients completing treatment (16) (P=.0010). The odds ratio for transplant in patients with baseline MELD ≥20 was 13.8(95%CI 2.78-69.04). CONCLUSIONS: SVR12 rates with sofosbuvir/daclatasvir in advanced liver disease are lower than in compensated disease. Although treatment improves MELD and Child-Pugh in most patients, a significant proportion will die or require transplantation. In those with MELD ≥20, it may be better to delay treatment until post-transplant.
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ItemSofosbuvir and velpatasvir with or without voxilaprevir in direct-acting antiviral-naïve chronic hepatitis C: patient-reported outcomes from POLARIS 2 and 3.(Wiley, 2018-01)BACKGROUND: Chronic hepatitis C infection leads to impairment of patient-reported outcomes (PROs). Treatment with direct-acting antiviral regimens results in short- and long-term improvement of these outcomes. AIM: To assess PROs in patients treated with a newly developed direct-acting antiviral, a fixed-dose combination of sofosbuvir/velpatasvir (SOF/VEL) with/without voxilaprevir (VOX). METHODS: The PRO data were collected from participants of POLARIS-2 and POLARIS-3 clinical trials (DAA-naïve, all HCV genotypes). Participants self-administered SF-36v2, FACIT-F, CLDQ-HCV and WPAI:SHP instruments at baseline, during treatment, and in follow-up. RESULTS: Of 1160 patients, 611 received SOF/VEL/VOX and 549 received SOF/VEL (52.8 ± 11.0 years, 55.9% male, 75.4% treatment-naïve, 33.9% cirrhotic). The sustained viral response at 12 weeks (SVR12) rates were 95%-98%. During treatment, improvements in most PRO scores were significant (all but one P < .01) and ranged from, on average, +2.3 to +15.0 points (on a 0-100 scale) by the end of treatment. These improvements were similar between SOF/VEL/VOX and SOF/VEL arms (all P > .05). After treatment discontinuation, patients treated with both regimens achieved significant and clinically meaningful PRO gains (+2.7 to +16.7 by post-treatment week 12, +3.9 to +20.1 by post-treatment week 24; all but one P < .001). Multivariate analysis showed that depression, anxiety and cirrhosis were the most consistent independent predictors of PRO impairment while no association of PROs with the treatment regimen choice was found (all P > .05). CONCLUSIONS: The pan-genotypic regimens with SOF/VEL with or without VOX not only have excellent efficacy and safety, but also significantly positively impact patients' experience both during treatment and after achieving sustained virologic response in DAA-naïve patients with HCV.
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ItemHBeAg levels at week 24 predict response to 8years of tenofovir in HBeAg-positive chronic hepatitis B patients(WILEY, 2018-01)BACKGROUND: Hepatitis B e antigen (HBeAg) seroconversion is a treatment endpoint for HBeAg-positive CHB, and a necessary precursor to HBsAg loss. Biomarkers that predict serological outcomes would be useful. AIM: To evaluate the utility of measuring HBeAg levels for predicting HBeAg seroconversion and HBsAg loss under long-term tenofovir (TDF) therapy. METHODS: A total of 266 patients were enrolled into a phase III study of TDF vs adefovir (ADV) for 48 weeks in HBeAg-positive patients, followed by open-label TDF up to 384 weeks. Serum HBeAg levels were measured for subjects with samples available at both baseline and week 24 of treatment (n = 200). Analysis compared subjects who achieved HBeAg seroconversion by week 384 vs no HBeAg seroconversion. RESULTS: HBeAg seroconversion rate was 52% by week 384. Time to HBeAg seroconversion was 80 weeks (IQR: 36-162). HBeAg decline at week 24 was associated with HBeAg seroconversion (1.63 vs 0.90 log10 PEIU/mL, P = .002). The optimal threshold for identifying HBeAg seroconversion was HBeAg decline ≥2.2 log10 PEIU/mL at week 24, with HBeAg seroconversion achieved by 76% of patients, compared to 44% if HBeAg decline <2.2 log10 (P < .0001). HBeAg decline ≥2.2 log10 PEIU/mL at week 24 was associated with HBsAg loss in genotype A or D patients (38% vs 15%, P = .03). Precore/basal core promotor variants were associated with lower baseline HBeAg levels, but not HBeAg seroconversion. CONCLUSION: Decline in HBeAg levels by week 24 was associated with HBeAg seroconversion and HBsAg loss in HBeAg-positive chronic hepatitis B patients treated with long-term TDF.
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ItemSofosbuvir-velpatasvir with ribavirin for 24 weeks in hepatitis C virus patients previously treated with a direct-acting antiviral regimen.(Ovid Technologies (Wolters Kluwer Health), 2017-10)UNLABELLED: The optimal retreatment strategy for patients chronically infected with hepatitis C virus who experience virologic failure after treatment with direct-acting antiviral-based therapies remains unclear. In this multicenter, open-label, phase 2 study, we evaluated the efficacy and safety of a fixed-dose combination of sofosbuvir-velpatasvir (400 mg/100 mg) plus weight-adjusted ribavirin administered for 24 weeks in patients who did not achieve sustained virologic response after prior treatment with direct-acting antiviral regimens that included the nucleotide analogue nonstructural protein 5B inhibitor sofosbuvir plus the nonstructural protein 5A inhibitor velpatasvir with or without the nonstructural protein 3/4A protease inhibitor voxilaprevir. The primary efficacy endpoint was the proportion of patients achieving sustained virologic response at 12 weeks after the cessation of treatment. In total, 63 of 69 (91%; 95% confidence interval, 82%-97%) patients achieved sustained virologic response at 12 weeks, including 36 of 37 (97%; 95% confidence interval, 86%-100%) patients with hepatitis C virus genotype 1 infection, 13 of 14 (93%; 95% confidence interval, 66%-100%) patients with genotype 2 infection, and 14 of 18 (78%; 95% confidence interval, 52%-94%) patients with genotype 3 infection. Most adverse events were of mild or moderate severity. The most frequently reported adverse events were fatigue, nausea, headache, insomnia, and rash. One patient (1%) with genotype 1a infection discontinued all study drugs due to an adverse event (irritability). CONCLUSION: Retreatment of patients who previously failed direct-acting antiviral-based therapies with sofosbuvir-velpatasvir plus ribavirin for 24 weeks was well tolerated and effective, particularly those with hepatitis C virus genotype 1 or 2 infection. (Hepatology 2017;66:1083-1089).