PRISM :: Browsing by Author "Hill, Michael D."

Browsing by Author "Hill, Michael D."

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Open Access
A Psychological Perspective on Image Interpretation in Acute Ischemic Stroke: Factors Affecting Non-Contrast CT ASPECTS Reliability
(2018-06-27) Wilson, Alexis Terrin Connett; Menon, Bijoy K.; Demchuk, Andrew M.; Hill, Michael D.; Saposnik, Gustavo
The Alberta Stroke Program Early CT Score (ASPECTS) is a semiquantitative scale to assess the extent of early ischemic changes on non-contrast CT in acute ischemic stroke patients. This is crucial for prognostication and treatment selection. Recent studies have revealed significant heterogeneity in reported measures of inter-rater reliability in ASPECTS, and this thesis aims to investigate the reasons underlying this phenomenon from the perspective of clinicians’ cognitive processes. First, this work explores relevant topics in the psychology of image interpretation and, on this psychological basis, proposes potential causes of inconsistent ASPECTS reliability. Possible strategies to improve clinicians’ inter- and intra-rater reliability are also discussed. The effect of image reading context variables and rater expertise on ASPECTS inter-rater reliability was then investigated. Raters of different experience levels scored ASPECTS on baseline non-contrast CT scans under three prior-information conditions (NCCT only, NCCT with access to clinical information, NCCT with access to clinical information and multiphase CT angiography) and three reading-context conditions (high/low ambient light, time pressure). The results indicate that these variables have the capacity to affect ASPECTS reliability. This work highlights the importance of acknowledging that medical image interpretation can be influenced by seemingly irrelevant external and internal factors like reading environment characteristics or physician-level variables. Giving more consideration to these variables in clinical and educational settings could improve the utility of tools like ASPECTS.
Open Access
A scoping review of the globally available tools for assessing health research partnership outcomes and impacts
(2023-12-22) Mrklas, Kelly J.; Boyd, Jamie M.; Shergill, Sumair; Merali, Sera; Khan, Masood; Moser, Cheryl; Nowell, Lorelli; Goertzen, Amelia; Swain, Liam; Pfadenhauer, Lisa M.; Sibley, Kathryn M.; Vis-Dunbar, Mathew; Hill, Michael D.; Raffin-Bouchal, Shelley; Tonelli, Marcello; Graham, Ian D.
Abstract Background Health research partnership approaches have grown in popularity over the past decade, but the systematic evaluation of their outcomes and impacts has not kept equal pace. Identifying partnership assessment tools and key partnership characteristics is needed to advance partnerships, partnership measurement, and the assessment of their outcomes and impacts through systematic study. Objective To locate and identify globally available tools for assessing the outcomes and impacts of health research partnerships. Methods We searched four electronic databases (Ovid MEDLINE, Embase, CINAHL + , PsychINFO) with an a priori strategy from inception to June 2021, without limits. We screened studies independently and in duplicate, keeping only those involving a health research partnership and the development, use and/or assessment of tools to evaluate partnership outcomes and impacts. Reviewer disagreements were resolved by consensus. Study, tool and partnership characteristics, and emerging research questions, gaps and key recommendations were synthesized using descriptive statistics and thematic analysis. Results We screened 36 027 de-duplicated citations, reviewed 2784 papers in full text, and kept 166 studies and three companion reports. Most studies originated in North America and were published in English after 2015. Most of the 205 tools we identified were questionnaires and surveys targeting researchers, patients and public/community members. While tools were comprehensive and usable, most were designed for single use and lacked validity or reliability evidence. Challenges associated with the interchange and definition of terms (i.e., outcomes, impacts, tool type) were common and may obscure partnership measurement and comparison. Very few of the tools identified in this study overlapped with tools identified by other, similar reviews. Partnership tool development, refinement and evaluation, including tool measurement and optimization, are key areas for future tools-related research. Conclusion This large scoping review identified numerous, single-use tools that require further development and testing to improve their psychometric and scientific qualities. The review also confirmed that the health partnership research domain and its measurement tools are still nascent and actively evolving. Dedicated efforts and resources are required to better understand health research partnerships, partnership optimization and partnership measurement and evaluation using valid, reliable and practical tools that meet partners’ needs.
Open Access
A Spatial Epidemiological Analysis of Stroke in Alberta, Canada, Using GIS.
(2015-01-08) van Rheenen, Susan M.; Hill, Michael D.; Watson, Tim W.J.
Stroke is the potentially devastating result of a sudden interruption of blood flow to the brain. It is a leading cause of death and disability world wide and incidence is expected to increase due to an aging population and increased prevalence in risk factors. Epidemiological research can enhance our understanding of stroke as a health problem in the population with respect to the extent of disease incidence and prevalence, the efficacy of health care delivery for stroke prevention and acute care, and to inform public health policy and planning. Geographic Information Systems (GIS) technology and spatial methods provide the means to store and retrieve spatially indexed health data, display the spatial information in maps, and conduct analyses examining health service delivery and utilization. The overall objective of this research is to enrich our current understanding of stroke as a health problem in the province of Alberta, Canada. This thesis is comprised of three studies. The first study utilized GIS-based methods and administrative datasets to identify and locate significant clusters of high and low rates of the major stroke types and in-hospital mortality. Important questions were raised regarding why regional differences exist and how disparities might be mitigated. The second study expanded upon the cluster analysis with an examination of associations between selected predictors and stroke and mortality hot and cold spots, mortality at the individual level, and recurrent stroke, using multivariable logistic regression. Distance from specialized stroke care was a significant predictor of index and recurrent stroke and mortality. EMS transport and Comprehensive Stroke Centre care significantly lowered the odds of stroke mortality. The third study employed spatial methods to evaluate the concordance of GIS predicted versus actual EMS ground transport times and to estimate the proportion of the Alberta population with potential and realized access to stroke care within critical time windows. GIS methods predicted ground transport time with reasonable accuracy and there was expanded access to stroke care over a 5-year time span. This research highlights the benefits of incorporating spatial methods and GIS in epidemiological research to elucidate how and to what extent place matters to health.
Open Access
Cerebral Small Vessel Disease: Cognitive Reserve and Mediators of Cognitive Decline
(2021-09-24) Durrani, Romella; Smith, Eric E.; Ismail, Zahinoor; Hill, Michael D.; Monchi, Oury; Dukelow, Sean P.; Postuma, Ronald B.
Background: Cerebral small vessel disease (CSVD) is the most common type of cerebrovascular disease that contributes to cognitive decline and dementia. However, persons with the same burden of CSVD often have different cognitive outcomes. Cognitive reserve, defined as the ability to tolerate or adapt to pathology, has been suggested to explain these variations. There are limited studies on cognitive reserve in CSVD, as most studies have focused on Alzheimer’s disease (AD). These studies have also focused on education as the proxy of cognitive reserve, with only a few studies looking at other proxies, such as occupation and leisure activities. Additionally, few studies of cognitive reserve have examined other measures of cerebrovascular disease, beyond white matter hyperintensities (WMH). Objectives: Determine whether cognitive reserve mitigates the deleterious effects of CSVD on cognition, and determine the degree to which cerebral amyloid angiopathy (CAA) biomarkers mediate the effects of CAA on cognition.Methods: Data were analyzed from four multicenter, cross-sectional cohorts. Measures of cerebrovascular disease included: brain infarcts, non-lacunar covert brain infarcts (CBI), WMH, vascular lesion burden, and CAA. Measures of cognitive reserve included: education, occupation, social involvement, physical activity, leisure physical activity, household income, marital status, height, stress, and multilingualism. CAA biomarkers included: WMH, cerebrovascular reactivity (CVR), peak width of skeletonized mean diffusivity (PSMD), mean cortical thickness, and mean cortical thickness in an AD meta-region of interest.Results: WMH, non-lacunar CBI, vascular lesion burden, and CAA were associated with lower cognition. Proxies of cognitive reserve were associated with higher cognition. However, cognitive reserve did not modify the association between CSVD and cognition. CVR, PSMD, and mean cortical thickness in regions typically affected by AD accounted for half of the effects of CAA on cognition; PSMD was the largest contributor.Conclusions: This forms the largest body of work on cognitive reserve within CSVD. Strategies to prevent CSVD-related cognitive decline and dementia include: 1) preventing CSVD, 2) enhancing cognitive reserve, thereby independently increasing cognition---however, this does not mitigate the deleterious effects of CSVD on cognition, and 3) in CAA, maintaining white matter integrity and restoring normal cerebrovascular reactivity.
Open Access
Characterizing Plasma Biomarkers of Cerebral Amyloid Angiopathy
(2024-07-26) Muir, Ryan Thomas; Smith, Eric E.; Hill, Michael D.; Black, Sandra E.; Hsuing, Robin
BACKGROUND: Cerebral Amyloid Angiopathy (CAA) is characterized by the progressive deposition of beta-amyloid in cortical and leptomeningeal small vessels leading to hemorrhagic stroke and dementia. While CAA is diagnosed using Boston Criteria 2.0, they are not always possible to apply. Plasma biomarkers (Aβ42, Aβ40, phosphorylated-tau (p-tau), neurofilament light chain (NfL) and Glial Fibrillary Acidic Protein (GFAP)) might improve diagnostic accuracy. This study evaluates whether plasma biomarkers: (i) differ in CAA compared to controls (ii) discriminate a diagnosis of CAA individually and in combination and (iii) are associated with cognition and neuroimaging biomarkers. METHODS: Data are from a multi-centre cohort study of participants with probable CAA and healthy controls. Participants had plasma collected and underwent neurocognitive evaluation and magnetic resonance imaging. Aβ was quantified with two independent methods: immunoprecipitation mass-spectrometry (IPMS) and single molecule array assay (Simoa). Plasma p-tau181, NfL and GFAP were quantified with Simoa. Neuroimaging biomarkers of small vessel disease, atrophy, white matter integrity and cerebrovascular reactivity (CVR) were quantified. Logistic regression was used to compute areas under the receiver operating characteristic curve (AUC) to assess biomarker discriminative performance of ascertaining a diagnosis of CAA. Associations between plasma biomarkers, cognition and neuroimaging biomarkers were evaluated with generalized linear models. RESULTS: 45 participants with CAA and 47 controls were eligible. With both methods, the Aβ42/40 ratio was reduced in CAA compared to controls. Furthermore, those with CAA had elevated p-tau181 and NfL. A combination of Aβ42/40 (Simoa), p-tau181, and NfL resulted in an AUC of 0.90. Reduced Aβ42/40 was associated with poorer speed of processing. Increasing NfL was associated with reduced Montreal Cognitive Assessment Scores, lower CVR and increasing CAA severity. CONCLUSIONS: This study identified differences in plasma Aβ42/40, p-tau181 and NfL in CAA compared and provides evidence that a panel of these biomarkers can achieve excellent diagnostic discriminability. This study also demonstrates that a marker of cerebral amyloidosis (Aβ42/40) is associated with speed of processing difficulties in those with CAA, while NfL was associated with global cognition, CAA severity and CVR. Overall, plasma biomarkers might, in future, help improve the evaluation and detection of CAA.
Open Access
Current practice and attitudes of stroke physicians towards rhythm-control therapy for stroke prevention: results of an international survey
(2023-07-06) Jensen, Märit; Al-Shahi Salman, Rustam; Ng, G. A.; van der Worp, H. B.; Loh, Peter; Campbell, Bruce C. V.; Kalman, Jonathan M.; Hill, Michael D.; Sposato, Luciano A.; Andrade, Jason G.; Metzner, Andreas; Kirchhof, Paulus; Thomalla, Götz
Abstract Background Patients with ischemic stroke and atrial fibrillation (AF) are at particularly high risk for recurrent stroke and cardiovascular events. Early rhythm control has been shown to be superior to usual care for the prevention of stroke and cardiovascular events for people with early AF. There are no data on the willingness to use rhythm control for patients with AF and acute ischemic stroke in clinical practice. Methods An online survey was carried out among stroke physicians to assess current practice and attitudes toward rhythm control in patients with AF and acute ischemic stroke between December 22nd 2021 and March 24th 2022. Results The survey was completed by 277 physicians including 237 from 15 known countries and 40 from unspecified countries. 79% (210/266) reported that they do not regularly apply treatment for rhythm control by ablation or antiarrhythmic drugs at all or only in small numbers (≤ 10%) of patients with AF and acute ischemic stroke. In those patients treated with rhythm-control therapy, antiarrhythmic drugs were used by the majority of respondents (89%), while only a minority reported using AF ablation (11%). 88% of respondents (221/250) stated that they would be willing to randomize patients with AF after acute ischemic stroke to either early rhythm control or usual care in a clinical trial. Conclusion Despite its potential benefit, few patients with AF and acute ischemic stroke appear to be treated with rhythm control, which may result from uncertainty regarding potential complications of antiarrhythmic therapy in patients with acute stroke. Together with recent data on the effectiveness of early rhythm control in patients with a history of stroke, these results call for a randomized clinical trial to assess the efficacy of early rhythm control in patients with acute ischemic stroke and AF.
Open Access
Drip and Ship versus Mothership: Transportation and Treatment Strategies for Acute Ischemic Stroke Patients
(2019-07-22) Holodinsky, Jessalyn Kathryn; Hill, Michael D.; Williamson, Tyler S.; Demchuk, Andrew M.; Patel, Alka B.
Ischemic stroke with large vessel occlusion can be treated with alteplase and/or endovascular therapy. While endovascular therapy has been proven more effective than alteplase the administration of both treatments is highly time sensitive. There are geographic disparities in access to endovascular therapy. For patients outside the immediate vicinity of a hospital equipped to perform endovascular therapy it is unknown whether transport directly to an endovascular center for alteplase and endovascular therapy (mothership) or transport to the closest centre for immediate alteplase treatment followed by transfer to the endovascular center (drip-and-ship) will result in best patient outcomes. In this thesis, this is explored using theoretical conditional probability. Models were generated using existing data from clinical trials of stroke treatment, the accuracy of prehospital large vessel occlusion screening tools, and time from onset to stroke treatment (a function of both geography and hospital efficiency). The models were used to determine which strategy predicts the greatest probability of excellent outcome for stroke patients in several different scenarios. The optimal transport strategy is influenced by three different factors, the impact of which is summarized as follows from the perspective of the drip and ship approach. First, the most probable diagnosis of the patient. As the positive predictive value of the large vessel occlusion screening tool decreases the importance of the drip and ship model is appreciated. Second, the speed of treatment at the receiving hospitals. Fast treatment at thrombolysis centres is key for the drip and ship model to remain viable. Finally, the patient’s travel time to and between the different hospitals. As the distance between the thrombolysis and endovascular centre increases again the importance of the drip and ship model is realized. This thesis presents a novel way of conceptualizing the pre-hospital transport of suspected stroke patients. Decision-making for pre-hospital transport can be modelled using existing clinical trial data; these models can be dynamically adapted to changing realities. As the radius of superiority of the different transport strategy is context specific regional customization transport protocols for stroke patients is essential.
Open Access
Evidence for the Appropriate Testing and Implementation of New Therapies for Intracerebral Hemorrhage in Canada
(2012) Specogna, Adrian Vladimir; Hill, Michael D.; Patten, Scott B.
Open Access
Expanding the evidence of endovascular treatment for acute ischemic stroke: patient–centered outcomes, population–level impact, and patients presenting with mild stroke symptoms
(2020-10-06) Zerna, Anna Charlotte; Hill, Michael D.; Demchuck, Andrew M.; Rabi, Doreen M.
Endovascular treatment (EVT) for anterior circulation acute ischemic stroke due to large‐vessel occlusion is the new standard of care resulting in reduced disability compared to medical treatment. Practice guidelines recommend the use of EVT but can only speak to the evidence provided by clinical trials and might not be appropriate when complex medical decisions need to consider the heterogeneity of patients in routine clinical care. Brought about by the limitations of the clinical trials, the work described in this doctoral thesis aimed to assess the long–term sustainability of efficacy of EVT, the utilization of post–stroke outcomes that are patient–centered and more meaningful to affected individuals, and the effectiveness of EVT in patient populations that have not been part of clinical trial cohorts. These are commonly older patients with comorbidities and patients presenting with mild stroke symptoms. The miFUNCTION scale was shown to display greater granularity in the mild to moderately–severe disability range post–stroke compared to the modified Rankin Scale and thus provide more insight into the patient's ability and capacity to engage in meaningful life roles after EVT. In a population–based analysis, adult patients undergoing EVT spent on average more than one week longer at home within the first 90 days compared with patients receiving medical treatment. Home‐time was used as a novel, health‐economic, and patient‐centered outcome. For patients presenting with mild symptoms, EVT resulted in similar 90–day outcomes compared to medical management despite an increased risk of neurological deterioration at 24 hours. Due to uncertainty regarding the risk–benefit–ratio, a well–designed clinical trial will need to establish how best to treat these patients. Overall, the work described here provides greater understanding of how the benefits and risks of EVT might vary across the population and differ from the rather homogenous patient cohort that has been assessed in the clinical trials. The results of this research will be meaningful to patients who experience acute ischemic strokes caused by large vessel occlusion and also aid with economic and regulatory decisions to more broadly offer and organize EVT across Alberta and beyond.
Open Access
Factors Associated with Early Deterioration after Spontaneous Intracerebral Hemorrhage: A Systematic Review and Meta-Analysis
(Public Library of Science (PLoS), 2014-05-08) Adrian V. Specogna; Turin, Tanvir C.; Patten, Scott B.; Hill, Michael D.
Open Access
Final 2 year results of the vascular imaging of acute stroke for identifying predictors of clinical outcome and recurrent ischemic eveNts (VISION) study
(BioMed Central, 2011-04-23) Coutts, Shelagh B.; Hill, Michael D.; Eliasziw, Misha; Fischer, Karyn; Demchuk, Andrew M.
Open Access
How are health research partnerships assessed? A systematic review of outcomes, impacts, terminology and the use of theories, models and frameworks
(2022-12-14) Mrklas, Kelly J.; Merali, Sera; Khan, Masood; Shergill, Sumair; Boyd, Jamie M.; Nowell, Lorelli; Pfadenhauer, Lisa M.; Paul, Kevin; Goertzen, Amelia; Swain, Liam; Sibley, Kathryn M.; Vis-Dunbar, Mathew; Hill, Michael D.; Raffin-Bouchal, Shelley; Tonelli, Marcello; Graham, Ian D.
Abstract Background Accurate, consistent assessment of outcomes and impacts is challenging in the health research partnerships domain. Increased focus on tool quality, including conceptual, psychometric and pragmatic characteristics, could improve the quantification, measurement and reporting partnership outcomes and impacts. This cascading review was undertaken as part of a coordinated, multicentre effort to identify, synthesize and assess a vast body of health research partnership literature. Objective To systematically assess the outcomes and impacts of health research partnerships, relevant terminology and the type/use of theories, models and frameworks (TMF) arising from studies using partnership assessment tools with known conceptual, psychometric and pragmatic characteristics. Methods Four electronic databases were searched (MEDLINE, Embase, CINAHL Plus and PsycINFO) from inception to 2 June 2021. We retained studies containing partnership evaluation tools with (1) conceptual foundations (reference to TMF), (2) empirical, quantitative psychometric evidence (evidence of validity and reliability, at minimum) and (3) one or more pragmatic characteristics. Outcomes, impacts, terminology, definitions and TMF type/use were abstracted verbatim from eligible studies using a hybrid (independent abstraction–validation) approach and synthesized using summary statistics (quantitative), inductive thematic analysis and deductive categories (qualitative). Methodological quality was assessed using the Quality Assessment Tool for Studies with Diverse Designs (QATSDD). Results Application of inclusion criteria yielded 37 eligible studies. Study quality scores were high (mean 80%, standard deviation 0.11%) but revealed needed improvements (i.e. methodological, reporting, user involvement in research design). Only 14 (38%) studies reported 48 partnership outcomes and 55 impacts; most were positive effects (43, 90% and 47, 89%, respectively). Most outcomes were positive personal, functional, structural and contextual effects; most impacts were personal, functional and contextual in nature. Most terms described outcomes (39, 89%), and 30 of 44 outcomes/impacts terms were unique, but few were explicitly defined (9, 20%). Terms were complex and mixed on one or more dimensions (e.g. type, temporality, stage, perspective). Most studies made explicit use of study-related TMF (34, 92%). There were 138 unique TMF sources, and these informed tool construct type/choice and hypothesis testing in almost all cases (36, 97%). Conclusion This study synthesized partnership outcomes and impacts, deconstructed term complexities and evolved our understanding of TMF use in tool development, testing and refinement studies. Renewed attention to basic concepts is necessary to advance partnership measurement and research innovation in the field. Systematic review protocol registration: PROSPERO protocol registration: CRD42021137932 https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=137932 .
Open Access
Machine learning models for functional impairment risk prediction in ischemic stroke patients
(2020-09-03) Alaka, Shakiru Ayomide; Sajobi, Tolulope T.; Menon, Bijoy K.; Hill, Michael D.; Williamson, Tyler S.
Background: Stroke-related functional impairment risk scores are commonly used to estimate the patient-specific risk of functional impairment in acute care settings. However, these models have been primarily developed based on regression models, which might not provide optimal predictive accuracy, especially when validated in an external cohort. Purpose: To evaluate the predictive accuracy of machine-learning (ML) models for predicting functional impairment risk in acute ischemic stroke patients. Second, to compare the predictive accuracy of machine-learning models and regression-based models using computer simulations. Methods: Using data from the Precise and Rapid Assessment of Collaterals with Multi-phase CT Angiography (PROVE-IT). The Modified Rankin Scale (mRS) score was used to assess the 90-day functional impairment status. The accuracy of machine-learning models such as random forest (RF), classification and regression tree (CART), support vector machine (SVM), C5.0 decision tree (DT), adaptive boost machine (ABM), and least absolute shrinkage and selection operator (LASSO) logistic regression, and logistic regression (LR) was used to predict the risk of patient-specific risk of 90-day functional impairment. Area under the receiver operating characteristic curve (AUC) sensitivity, specificity, Mathews correlation coefficient (MCC) and Brier score was used to assess the predictive accuracy of these models via internal cross-validation and external validation in the Identifying New Approaches to Optimize Thrombus Characterization for Predicting Early Recanalization and Reperfusion with IVtPA Using Serial CT Angiography (INTERSSeCT) cohort study. Monte Carlo methods were used to develop recommendations for selecting machine-learning models under a variety of data characteristics. Results: Both logistic regression and machine-learning models had comparable predictive accuracy when validated internally (AUC range = [0.65 – 0.72]; MCC range = [0.29 - 0.42]) and externally (AUC range = [0.66 – 0.71]; MCC range = [0.34 – 0.42]). However, regression-based had a fairly better calibration than the ML models. Our simulation study showed that ML and regression-based models are not equally robust to a variety of data analytic characteristics. LR models exhibited higher AUC in studies with a small/moderate set of predictors, while RF had about 15% higher discrimination studies with high dimensional set of predictors. ML models may be less accurate for predicting outcomes in studies with a few sets of predictors or when there is a large class imbalance in the data sets. Conclusions ML and regression-based algorithms are not equally sensitive to data analytic conditions, even though our data analysis revealed no significant differences between the former and the latter. ML might offer some discriminative advantages over the latter depending on the size and type of study predictors. We recommend that the choice between these classes of models should be guided by data characteristics, study design, and purpose for which the models are being developed.
Open Access
Passive Surveillance of Transient Ischemic Attacks in the Emergency Department: Validity of Administrative Data and Determinants of Inaccuracies in Data Coding
(2016) Yu, Amy Y. X.; Hill, Michael D.; Coutts, Shelagh B.; Quan, Hude; McRae, Andrew D.
Stroke is a leading cause of morbidity and transient ischemic attacks (TIA) are an ideal target for stroke prevention strategies. Administrative data are an important source of information for TIA research, but they have not been validated in the emergency department (ED). We aimed to determine the validity of TIA codes in the Canadian ED administrative database and the predictors of accurate TIA coding. We studied patients presenting to the ED with acute neurological symptoms. The National Ambulatory Care Reporting System (NACRS) database diagnosis codes were compared to the ED chart re-abstraction and 90-day final clinical diagnoses to obtain the sensitivity, specificity, and predictive values. The sensitivity of TIA codes was low to moderate (37-64%), but the specificity was high (82-93%). Quality of physician documentation was an important predictor of data accuracy. Our findings inform TIA research and surveillance methods and we identify an opportunity for improving administrative data quality.
Open Access
The Reliability and Sensitivity of the National Institutes of Health Stroke Scale for Spontaneous Intracerebral Hemorrhage in an Uncontrolled Setting
(Public Library of Science, 2013-12-19) Specogna, Adrian V.; Patten, Scott B.; Turin, Tanvir C.; Hill, Michael D.
Open Access
Siloed mentality, health system suboptimization and the healthcare symphony: a Canadian perspective
(2024-07-17) Lau, Robin S.; Boesen, Mari E.; Richer, Lawrence; Hill, Michael D.
Abstract Measuring and optimizing a health system is challenging when patient care is split between many independent organizations. For example, patients receive care from their primary care provider, outpatient specialist clinics, hospitals, private providers and, in some instances, family members. These silos are maintained through different funding sources (or lack of funding) which incentivize siloed service delivery. A shift towards prioritizing patient outcomes and keeping the patient at the centre of care is emerging. However, competing philosophies on patient needs, how health is defined and how health is produced and funded is creating and engraining silos in the delivery of health services. Healthcare and health outcomes are produced through a series of activities conducted by diverse teams of health professionals working in concert. Health professionals are continually learning from each patient interaction; however, silos are barriers to information exchange, collaborative evidence generation and health system improvement. This paper presents a systems view of healthcare and provides a systems lens to approach current challenges in health systems. The first part of the paper provides a background on the current state and challenges to healthcare in Canada. The second part presents potential reasons for continued health system underperformance. The paper concludes with a system perspective for addressing these challenges.
Embargo
Some Contributions to Understanding the Heterogeneity of Treatment Effects in Stroke Trials
(2024-06-20) Ademola, Ayoola; Sajobi, Tolulope; Hildebrand, Kevin A.; Hill, Michael D.; Thabane, Lehana
Background: Stroke is a neurological disease that is the third leading cause of death and the tenth-largest known cause of disability-adjusted life years in Canada. Fortunately, clinical trial evidence has identified a few treatments that improve patients’ outcomes, resulting in faster reperfusion, better functional outcomes, lower mortality rates, and improved quality of life. Despite the overall positive benefits of these interventions, there remain differences in the impact of the treatment at the individual level, with some patients experiencing positive benefits and others showing neutral or adverse effects of interventions. Such heterogeneity of treatment effects (HTE) could be attributed to differences in patients’ socio-demographic or clinical characteristics, study designs, inclusion/exclusion criteria, and geographic or regional healthcare systems. Conventional statistical approaches for accounting for within-study and between-study HTE have primarily relied on within-trial subgroup analysis and meta-analysis. However, these approaches are limited because they are based on restrictive distributional assumptions, which may only be tenable in some clinical trials. Methods: This dissertation investigates relevant methodologies for characterizing and accommodating treatment effects within- and between-study heterogeneity in stroke trials. The specific objectives of this dissertation are to: 1) assess the credibility of subgroup analyses reported in published stroke trials; 2) investigate the comparative performance of methods for subgroup identification in clinical trials with binary endpoints when there is no a priori knowledge of patients’ characteristics associated with HTE, and 3) examine the performance of random-effects models when synthesizing evidence from trials with different study design characteristics. This study uses a combination of knowledge synthesis methodology and computer simulations to address these objectives. For objective 1, we conducted a systematic review to examine the credibility of reported subgroups in stroke trials. We used the Instrument for Assessing the Credibility of Effect Modification Analyses (ICEMAN) checklist to evaluate the quality of the subgroup analyses conducted for each study. For Objectives 2 and 3, computer simulations were used to examine the comparative performance of subgroup identification methods for identifying relevant variables/biomarkers associated with HTE in clinical trials of binary endpoints and meta-analytic methods for synthesizing treatment effects obtained from explanatory and pragmatic trials, respectively. Results: The systematic review of reporting quality of subgroup analyses in stroke trials revealed that the credibility of reported subgroup analyses is poor, with most studies not providing a priori rationale for the type and number of subgroup analyses conducted. Among all the subgroup identification methods investigated, the model-based recursive partitioning (MOB) method had the best control of Type I and higher statistical power to detect HTE. The random-effects model based on t-distribution (robustRE) and the mixture random-effects model (mixRE) are more appropriate for meta-analysis data with substantial HTE. However, the conventional random-effects model (RE model) remains reliable for estimating pooled treatment effects in data with moderate HTE. Conclusion: Understanding and capturing treatment effect heterogeneity is critical for generating evidence about treatment effectiveness in clinical trials. More statistical methods that account for heterogeneity in the study population and design characteristics are recommended to analyze and synthesize evidence from clinical trials.
Open Access
Surveillance Of Stroke Occurrence in the Calgary Health Region during 1995 - 2004
(2008) Zhu, Haifeng; Hill, Michael D.
Open Access
The Brain in Motion II Study: study protocol for a randomized controlled trial of an aerobic exercise intervention for older adults at increased risk of dementia
(2021-06-14) Krüger, Renata L.; Clark, Cameron M.; Dyck, Adrienna M.; Anderson, Todd J.; Clement, Fiona; Hanly, Patrick J.; Hanson, Heather M.; Hill, Michael D.; Hogan, David B.; Holroyd-Leduc, Jayna; Longman, R. S.; McDonough, Meghan; Pike, G. B.; Rawling, Jean M.; Sajobi, Tolulope; Poulin, Marc J.
Abstract Background There remains no effective intervention capable of reversing most cases of dementia. Current research is focused on prevention by addressing risk factors that are shared between cardiovascular disease and dementia (e.g., hypertension) before the cognitive, functional, and behavioural symptoms of dementia manifest. A promising preventive treatment is exercise. This study describes the methods of a randomized controlled trial (RCT) that assesses the effects of aerobic exercise and behavioural support interventions in older adults at increased risk of dementia due to genetic and/or cardiovascular risk factors. The specific aims are to determine the effect of aerobic exercise on cognitive performance, explore the biological mechanisms that influence cognitive performance after exercise training, and determine if changes in cerebrovascular physiology and function persist 1 year after a 6-month aerobic exercise intervention followed by a 1-year behavioural support programme (at 18 months). Methods We will recruit 264 participants (aged 50–80 years) at elevated risk of dementia. Participants will be randomly allocated into one of four treatment arms: (1) aerobic exercise and health behaviour support, (2) aerobic exercise and no health behaviour support, (3) stretching-toning and health behaviour support, and (4) stretching-toning and no health behaviour support. The aerobic exercise intervention will consist of three supervised walking/jogging sessions per week for 6 months, whereas the stretching-toning control intervention will consist of three supervised stretching-toning sessions per week also for 6 months. Following the exercise interventions, participants will receive either 1 year of ongoing telephone behavioural support or no telephone support. The primary aim is to determine the independent effect of aerobic exercise on a cognitive composite score in participants allocated to this intervention compared to participants allocated to the stretching-toning group. The secondary aims are to examine the effects of aerobic exercise on a number of secondary outcomes and determine whether aerobic exercise-related changes persist after a 1-year behavioural support programme (at 18 months). Discussion This study will address knowledge gaps regarding the underlying mechanisms of the pro-cognitive effects of exercise by examining the potential mediating factors, including cerebrovascular/physiological, neuroimaging, sleep, and genetic factors that will provide novel biologic evidence on how aerobic exercise can prevent declines in cognition with ageing. Trial registration ClinicalTrials.gov NCT03035851 . Registered on 30 January 2017
Open Access
The Safety and Cost-Effectiveness of Carotid Angioplasty and Stenting in Calgary
(2012-09-28) Almekhlafi, Mohammed; Hill, Michael D.
Objectives To evaluate the safety and cost of carotid stenting in Calgary. Methods A cost-utility analysis from the perspective of the Canadian health care system was performed comparing stenting to endarterectomy using a decision analytic model. A prospective cohort study was done for trans cranial Doppler monitoring during stenting procedures. Findings were correlated with 24-hour MRI brain lesions using a binomial regression model. Results Stenting was more expensive than endarterectomy ($6106.84 incremental cost) and had a lower effectiveness (- 0.12 QALYs). Results were influenced by the procedure costs and were sensitive to patients’ characteristics. In 26 subjects who underwent stenting, MRI lesions were detected in 76%. Procedural monitoring showed a median of 224.5 emboli. Large emboli correlated with MRI lesions after adjusting for age and symptoms status. Conclusion To improve the outcomes of carotid stenting, research should aim to improve the procedure safety without increasing its costs.