Abstract Introduction Cystectomy with urinary diversion (i.e. bladder removal surgery) is commonly studied using large health administrative databases. These databases often use diagnoses or procedure codes with unknown accuracy to identify cystectomy patients, thereby resulting in significant misclassification bias. The primary objective of this study is to develop a predictive model that will return an accurate probability that patients recorded in the discharge abstract database have undergone cystectomy with urinary diversion, stratified by type of urinary diversion (continent vs incontinent). Secondary objectives of this study include: 1) to internally validate our predictive model to determine its accuracy using a cohort of all adults admitted to The Ottawa Hospital (TOH) within the study period; and 2) compare the accuracy of this model to that of code-based algorithms used previously in published studies to identify cystectomy. Methods A gold standard reference cohort (GSC) of all patients who underwent cystectomy and urinary diversion at TOH between 2009 and 2019 was created by using the SIMS registry within the TOH data warehouse which captures all primary surgical procedures performed. The GSC was then confirmed by manual chart review to ensure accuracy. Through ICES, the GSC was linked to the provincial Discharge Abstract Database (DAD), physician billing records (OHIP), and Ontario Cancer Registry (OCR) and a new combined dataset containing all admissions at TOH during the study period was created. Clinical information, billing, and intervention codes within these databases were reviewed and the co-variables thought to be predictive of cystectomy were selected a priori. A multinomial logistic regression model (i.e. The Ottawa Cystectomy Identification Model or OCIM) was created using these co-variables to determine the probability of a patient undergoing cystectomy, stratified by continent vs incontinent diversion, during an admission in the DAD. Using the OCIM and bootstrap imputation methods, co-variable values and 95% confidence intervals were calculated. The values of these same co- variables were then measured using a code algorithm (the presence of either a procedure code or billing code for cystectomy with incontinent or continent diversion). Misclassification bias was then measured by comparing the values of co-variables using the OCIM or code algorithm to the true values obtained from the gold standard reference cohort. Results Five hundred patients were included in the GSC [median age 68.0 (IQR 13.0); 75.6% male; 55.6% incontinent diversion]. The prevalence of cystectomy within the DAD over the study period was 0.12% (500/428697 total admissions). Sensitivity and positive predictive values for cystectomy codes were 97.1% and 58.6% for incontinent diversions and 100.0% and 48.4% for continent diversions, respectively. The OCIM accurately predicted cystectomy with incontinent diversion (c-statistic [C] 0.999, Integrated Calibration Index [ICI] 0.000) and cystectomy with continent diversion (C:1.000, ICI 0.000) probabilities. Misclassification bias was lower when identifying cystectomy patients using the OCIM with bootstrap imputation compared to the use of the code algorithm alone. Conclusions A model using administrative data accurately returned the probability that cystectomy by diversion type occurred during a hospitalization. Using this model to impute cystectomy status minimized misclassification bias.

Introduction: The main objective of this thesis is to develop an algorithm to accurately identify cases of biopsy-proven Celiac Disease (CD) in children aged 6 months-14 years old from Ontario health administrative data. Method: CD cases diagnosed in 2005-2011 were identified from CHEO, and linked to the health administrative data to serve as reference for algorithms derivation. Algorithms based on outpatient physician visits for CD plus endoscopy billing code were constructed and tested. Results: The best algorithm selected based on performance from derivation study and clinical expertise consisted of an OHIP-based endoscopy billing claim followed by 1 or more adult or pediatric gastroenterologist encounters after the endoscopic procedure. The sensitivity, specificity, PPV, and NPV for the algorithm were 70.4%, >99.9%, 53.3% and >99.9% respectively. Conclusion: Study results suggest that the currently available Ontario health administrative data is not suitable for identifying incident pediatric CD cases.

In three chapters, I focus on how, and which, policy parameters of Canada’s public pension system affect seniors’ labour supply decisions. First, I study seniors’ labour supply responses to a series of reforms in 2012 and 2013 that incentivized many pensioners to extend their working lives; second, I assess how and whether receipt of public pension benefits affects seniors’ retirement timing differentially for those with different past earnings at ages 50-53; and, finally, I investigate older immigrants’ retirement and pension claiming decisions and how these decisions are impacted by permanent residency requirements for benefit eligibility. My analyses were carried out using income-tax and related panel data from the Longitudinal Administrative Databank (LAD), a 20% sample of taxpayers spanning the years 1982-2019 at the time of writing. In addition to detailed income-tax information, it contains information on receipt of non-taxable transfer income. / Dissertation / Candidate in Philosophy

Objectives: The objectives of this thesis were to: 1) develop and validate a coding algorithm to identify true cases of neonatal bacterial sepsis, and 2) apply the algorithm to calculate incidence rates and estimate temporal trends of neonatal bacterial sepsis. Methods: For Objective 1, the reference cohorts were assembled among neonates born in 2012-2017 using patient-level health care encounter data. Any neonates who met both the Diagnostic Criterion Ⅰ (microbiological confirmation) and Criterion Ⅱ (sepsis-related antibiotic administration) were included in the true-positive cohort. Potential coding algorithms were developed based on different combinations of ICD-10-CA codes on the hospitalization discharge abstract. For Objective 2, the coding algorithm with the most optimal characteristics was applied to provincial data to calculate incidence rates in Ontario during 2003-2017. Recent temporal trends were estimated by Poisson regression analysis. Results: In Objective 1, since all true-positive cases identified were born at preterm gestation, the study population in Objective 2 was limited to preterm infants. The final coding algorithm selected had sensitivity of 75.3% (95% CI, 66.8%-83.7%), specificity of 98.2% (95% CI, 97.8%-98.6%) and PPV of 50.0% (95% CI, 42.1%-58.0%). Using this algorithm, the annual incidence declined over time from 50.2 (95% CI, 45.4-55.4) per 1000 preterm infants in 2003 to 27.5 (95% CI, 20.4-36.9) per 1000 preterm infants in 2017. The trend over time was statistically significant with P-value <0.0001. Significant variation in bacterial sepsis incidence rates was noted across infant sex and gestational age. Conclusion: The coding algorithm developed in this study could not accurately identify neonates with bacterial sepsis from within health administrative database using the data available to us now. For the purpose of demonstrating the application of the algorithm, we carried out Objective 2; however, it is important to cautiously interpret the provincial rates given the the poor performance of the case-finding algorithm.

<p>Cardiovascular disease is a leading cause of death and hospitalizations in Canada. Most risk factors for cardiovascular disease are known, and many are modifiable. One such risk factor that often goes unrecognized is non-adherence. Pharmacists are ideally positioned to have an influence on cardiovascular risk reduction, including supporting medication adherence; however it is still unknown whether typical (non-specialist) pharmacists can provide strategies that are effective and sustainable in todays health care system. Thus, the overall objective of this research project was to determine what interventions typical pharmacists can adopt to effectively facilitate cardiovascular risk reduction within the constraints of the current practice environment. This objective was accomplished through 4 related studies: 1) a randomized controlled trial involving a pharmacist-directed cardiovascular risk reduction collaboration within a family physician practice; 2) a systematic review identifying and evaluating published interventions by community pharmacists for cardiovascular disease or diabetes; 3) the design of a pilot study evaluating a novel community pharmacy intervention aimed at cardiovascular risk reduction and; 4) the examination of adherence patterns among antihypertensive medication users to identify associated factors and high-risk periods for non-adherence.</p> <p>Although the randomized controlled trial did not show a statistically significant benefit of the pharmacist intervention on cardiovascular risk, it did demonstrate the feasibility of incorporating a pharmacist into a collaborative role, without the need for an advanced or specialized degree. Results from the systematic review yielded several studies involving community pharmacists and cardiovascular disease or diabetes. However, the majority of these studies were of poor quality, evaluated complex and intensive interventions, and provided questionable clinical benefits. The design of the pilot study demonstrated the feasibility of developing high quality, robust research involving community pharmacists. Finally, the observational study examining adherence patterns to antihypertensive agents revealed two important findings that can guide the development of future strategies to support adherence: the first year of therapy, and particularly the first dispensation, is a critical time for the development of non-adherence and, contrary to previously published studies, adherence is similar between all classes of antihypertensive medications.</p> <p>This program of research did not identify one particular pharmacist intervention as being superior for cardiovascular risk reduction in todays practice environment. However, it did highlight the need for improved study quality and the development of interventions that are practical and can be realistically implemented by pharmacists in todays practice environment.</p>

<p>Cardiovascular disease is a leading cause of death and hospitalizations in Canada. Most risk factors for cardiovascular disease are known, and many are modifiable. One such risk factor that often goes unrecognized is non-adherence. Pharmacists are ideally positioned to have an influence on cardiovascular risk reduction, including supporting medication adherence; however it is still unknown whether typical (non-specialist) pharmacists can provide strategies that are effective and sustainable in todays health care system. Thus, the overall objective of this research project was to determine what interventions typical pharmacists can adopt to effectively facilitate cardiovascular risk reduction within the constraints of the current practice environment. This objective was accomplished through 4 related studies: 1) a randomized controlled trial involving a pharmacist-directed cardiovascular risk reduction collaboration within a family physician practice; 2) a systematic review identifying and evaluating published interventions by community pharmacists for cardiovascular disease or diabetes; 3) the design of a pilot study evaluating a novel community pharmacy intervention aimed at cardiovascular risk reduction and; 4) the examination of adherence patterns among antihypertensive medication users to identify associated factors and high-risk periods for non-adherence.</p> <p>Although the randomized controlled trial did not show a statistically significant benefit of the pharmacist intervention on cardiovascular risk, it did demonstrate the feasibility of incorporating a pharmacist into a collaborative role, without the need for an advanced or specialized degree. Results from the systematic review yielded several studies involving community pharmacists and cardiovascular disease or diabetes. However, the majority of these studies were of poor quality, evaluated complex and intensive interventions, and provided questionable clinical benefits. The design of the pilot study demonstrated the feasibility of developing high quality, robust research involving community pharmacists. Finally, the observational study examining adherence patterns to antihypertensive agents revealed two important findings that can guide the development of future strategies to support adherence: the first year of therapy, and particularly the first dispensation, is a critical time for the development of non-adherence and, contrary to previously published studies, adherence is similar between all classes of antihypertensive medications.</p> <p>This program of research did not identify one particular pharmacist intervention as being superior for cardiovascular risk reduction in todays practice environment. However, it did highlight the need for improved study quality and the development of interventions that are practical and can be realistically implemented by pharmacists in todays practice environment.</p>

There is limited data on mortality, health service use and costs following treatment of malignant pleural effusions (MPE) in the real-world setting. We performed a retrospective population-based study using health administrative data of adults with indwelling pleural catheter (IPC) insertion (n=4,574) or pleurodesis (n=1,235) for MPE between 2015 to 2019. Inverse probability of treatment weighting using the propensity score was performed to adjust for baseline characteristic imbalances. After weighting to balance on baseline characteristics, there was no significant difference in post-procedure mortality between individuals receiving IPCs and pleurodesis, with IPCs inserted significantly later after an initial cancer diagnosis. IPCs with home nursing drainage were associated with reduced subsequent health resource use and healthcare costs compared to pleurodesis. A protocol was developed for a future economic evaluation to compare the cost-effectiveness of the procedures. This thesis provides the foundation for further research to help optimize the treatment of individuals with MPEs.

This article contributes a framework for the quality assessment of imputations within a broader structure to evaluate the quality of register-based data. Four quality-related hyperdimensions examine the data processing from the raw-data level to the final statistics. Our focus lies on the quality assessment of different imputation steps and their influence on overall data quality. We suggest classification rates as a measure of accuracy of imputation and derive several computational approaches. (authors' abstract)

Antipsychotic use is an important issue in long-term care (LTC) homes due to their widespread use, the potential for serious adverse events and limited evidence about their efficacy in treating behavioural and psychological symptoms of dementia. Rates of antipsychotic use vary across LTC homes, but little is known about the contribution of physicians to this variation. This study documented the characteristics of physicians who regularly treated residents in Ontario LTC homes and examined variation in antipsychotic prescribing across physicians. In a population-based retrospective cohort of LTC residents, 637 (52.8%) of 1,207 LTC physicians cared for 46,365 (90.4%) of all residents. Overall, 27.3% of residents received antipsychotic therapy, but extremely high prescribers prescribed antipsychotics to 42.8% of their patients. Variation in physician antipsychotic prescribing persisted after controlling for clinical and behavioural resident characteristics. This variation was reduced by 47.1% when LTC homes were accounted for in multilevel cross-classification logistic regression models.

Antipsychotic use is an important issue in long-term care (LTC) homes due to their widespread use, the potential for serious adverse events and limited evidence about their efficacy in treating behavioural and psychological symptoms of dementia. Rates of antipsychotic use vary across LTC homes, but little is known about the contribution of physicians to this variation. This study documented the characteristics of physicians who regularly treated residents in Ontario LTC homes and examined variation in antipsychotic prescribing across physicians. In a population-based retrospective cohort of LTC residents, 637 (52.8%) of 1,207 LTC physicians cared for 46,365 (90.4%) of all residents. Overall, 27.3% of residents received antipsychotic therapy, but extremely high prescribers prescribed antipsychotics to 42.8% of their patients. Variation in physician antipsychotic prescribing persisted after controlling for clinical and behavioural resident characteristics. This variation was reduced by 47.1% when LTC homes were accounted for in multilevel cross-classification logistic regression models.