Propensity score based methods for estimating the treatment effects based on observational studies.

This dissertation consists of two interconnected research projects. The first project was a study of propensity scores based statistical methods for estimating the average treatment effect (ATE) and the average treatment effect among treated (ATT) when there are two treatment groups. The ATE is defined as the mean of the individual causal effects in the whole population, while ATT is defined as the treatment effect for the treated population. Propensity score based statistical methods, such as matching, regression, stratification, inverse probability weighting (IPW), and doubly robust (DR) methods were used to estimate the ATE and ATT. Simulation studies and case studies were conducted to examine the performances of propensity score based methods when propensity score was estimated using logistic regression and generalized boosted models (GBM). The aim of the second project is to develop generalized propensity score based statistical methods for estimating ATE when there are more than two treatment groups. The generalized propensity score was estimated using multinomial logistic regression, random forests, and GBM. In addition, an adaptive optimal ensemble method was developed to estimate the generalized propensity score. Once the generalized propensity scores were obtained, IPW, stratification, and DR methods were used to estimate the ATE. Simulation studies were conducted to examine the performances of these different generalized propensity score based methods. In addition, we applied these methods to examine the outpatients health care costs under different treatments for patients with spinal fusion

Cohort profile: the British Columbia COVID-19 Cohort (BCC19C)—a dynamic, linked population-based cohort

PurposeThe British Columbia COVID-19 Cohort (BCC19C) was developed from an innovative, dynamic surveillance platform and is accessed/analyzed through a cloud-based environment. The platform integrates recently developed provincial COVID-19 datasets (refreshed daily) with existing administrative holdings and provincial registries (refreshed weekly/monthly). The platform/cohort were established to inform the COVID-19 response in near “real-time” and to answer more in-depth epidemiologic questions.ParticipantsThe surveillance platform facilitates the creation of large, up-to-date analytic cohorts of people accessing COVID-19 related services and their linked medical histories. The program of work focused on creating/analyzing these cohorts is referred to as the BCC19C. The administrative/registry datasets integrated within the platform are not specific to COVID-19 and allow for selection of “control” individuals who have not accessed COVID-19 services.Findings to dateThe platform has vastly broadened the range of COVID-19 analyses possible, and outputs from BCC19C analyses have been used to create dashboards, support routine reporting and contribute to the peer-reviewed literature. Published manuscripts (total of 15 as of July, 2023) have appeared in high-profile publications, generated significant media attention and informed policy and programming. In this paper, we conducted an analysis to identify sociodemographic and health characteristics associated with receiving SARS-CoV-2 laboratory testing, testing positive, and being fully vaccinated. Other published analyses have compared the relative clinical severity of different variants of concern; quantified the high “real-world” effectiveness of vaccines in addition to the higher risk of myocarditis among younger males following a 2nd dose of an mRNA vaccine; developed and validated an algorithm for identifying long-COVID patients in administrative data; identified a higher rate of diabetes and healthcare utilization among people with long-COVID; and measured the impact of the pandemic on mental health, among other analyses.Future plansWhile the global COVID-19 health emergency has ended, our program of work remains robust. We plan to integrate additional datasets into the surveillance platform to further improve and expand covariate measurement and scope of analyses. Our analyses continue to focus on retrospective studies of various aspects of the COVID-19 pandemic, as well as prospective assessment of post-acute COVID-19 conditions and other impacts of the pandemic

Nitrite Biosensing via Selective Enzymes—A Long but Promising Route

The last decades have witnessed a steady increase of the social and political awareness for the need of monitoring and controlling environmental and industrial processes. In the case of nitrite ion, due to its potential toxicity for human health, the European Union has recently implemented a number of rules to restrict its level in drinking waters and food products. Although several analytical protocols have been proposed for nitrite quantification, none of them enable a reliable and quick analysis of complex samples. An alternative approach relies on the construction of biosensing devices using stable enzymes, with both high activity and specificity for nitrite. In this paper we review the current state-of-the-art in the field of electrochemical and optical biosensors using nitrite reducing enzymes as biorecognition elements and discuss the opportunities and challenges in this emerging market

ASCI 2010 contrast media guideline for cardiac imaging: a report of the Asian Society of Cardiovascular Imaging cardiac computed tomography and cardiac magnetic resonance imaging guideline working group

The use of contrast media for cardiac imaging becomes increasing as the widespread of cardiac CT and cardiac MR. A radiologist needs to carefully consider the indication and the injection protocol of contrast media to be used as well as the possibility of adverse effect. There are several guidelines for contrast media in western countries. However, these are focusing the adverse effect of contrast media. The Asian Society of Cardiovascular Imaging, the only society dedicated to cardiovascular imaging in Asia, formed a Working Group and created a guideline, which summarizes the integrated knowledge of contrast media for cardiac imaging. In cardiac imaging, coronary artery evaluation is feasible by non-contrast MR angiography, which can be an alternative examination in high risk patients for the use of iodine contrast media. Furthermore, the body habitus of Asian patients is usually smaller than that of their western counterparts. This necessitates modifications in the injection protocol and in the formula for calculation of estimated glomerular filtration rate. This guideline provided fundamental information for the use of contrast media for Asian patients in cardiac imaging

Familjesituationens hälsopåverkan i det svenska samhället

Denna uppsats undersöker sambandet mellan familjesituation och hälsa, samt undersöker om detta samband kan förklaras av andra faktorer såsom individens utbildningsnivå, socioekonomiska status, hälsorelaterade beteende och sociala nätverk. Uppsatsen undersöker också om sambandet varierar enligt individens utbildningsnivå. Metoden som används är en binär logistisk regressionsanalys av data från Levnadsnivåundersökning år 2000 (LNU 2000) för att kunna indikera dessa faktorer. Resultaten visar att det förekommer ett samband mellan familjesituation och hälsa. Resultaten visar även att övriga faktorer visar sig ha en direkt påverkan på hälsan. Slutsatsen är att familjesituationen spelar en betydande roll för individens hälsa. Däremot kunde uppsatsen inte bevisa att det förekommer någon signifikant interaktionseffekt mellan individens familjesituation och olika utbildningsnivåer. Denna studie kan vara en utgångspunkt för att forska vidare om sambandet mellan familjesituation och hälsa

A Comparative Study of Generalized Ratio and Regression Estimators with their classical counterparts

A comparative study has been made by using generalized ratio and regression estimators of Brewer, Horvitz and Thompson and Cassel-Sarandal and Wretman estimators. The study also involves ratio and regression estimators along with the mean per unit estimator of equal probability sampling. Ranking is being done to see which population total variances are performing the best