Publications by authors named "Sengwee Toh"

Introduction: This real-world study assessed the effectiveness of bebtelovimab (BEB) versus nirmatrelvir/ritonavir (NR) among outpatients with COVID-19 during the Omicron variant era.

Methods: We conducted a cohort study evaluating patients treated with BEB or NR from February to August 2022 (study period). Follow-up began the day after treatment and continued for 30 days.

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  • The study addresses the challenges of missing data in confounding variables when using real-world data, specifically in pharmaceutical research comparing cardiovascular outcomes between two types of diabetes medications in older adults.
  • Utilizing the Structural Missing Data Investigations (SMDI) toolkit, researchers analyzed the missingness patterns of important health metrics like HbA1c and BMI from electronic health records.
  • Results indicated significant missing data (63.6% for HbA1c and 16.5% for BMI) and demonstrated that missingness could be predicted and managed through statistical techniques, leading to improved estimates of medication effects.
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  • Most drug repurposing studies focus on validating existing ideas, but this study aimed to generate new hypotheses for sodium-glucose cotransporter-2 inhibitors (SGLT2i) using advanced statistical methods.
  • The researchers created a matched cohort of SGLT2i users and dipeptidyl peptidase-4 inhibitors (DPP4i) to analyze a large dataset of patient outcomes, identifying potential associations.
  • They found 18 notable signals that could indicate new uses for SGLT2i, including significant links to chronic kidney disease and anemia, which align with recent approvals but need further research for confirmation.*
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Epidemiologic studies frequently use risk ratios to quantify associations between exposures and binary outcomes. When the data are physically stored at multiple data partners, it can be challenging to perform individual-level analysis if data cannot be pooled centrally due to privacy constraints. Existing methods either require multiple file transfers between each data partner and an analysis center (e.

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Background: Antidepressants are among the most commonly prescribed medications, but evidence on comparative weight change for specific first-line treatments is limited.

Objective: To compare weight change across common first-line antidepressant treatments by emulating a target trial.

Design: Observational cohort study over 24 months.

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While many pregnant individuals use prescription medications, evidence supporting product safety during pregnancy is often inadequate. Existing electronic healthcare data sources provide large, diverse samples of health plan members to allow for the study of medical product utilization during pregnancy, as well as pregnancy, maternal, and infant outcomes. The Sentinel System is a national medical product surveillance system that includes administrative claims and electronic health record databases from large national and regional health insurers.

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Objective: Partially observed confounder data pose challenges to the statistical analysis of electronic health records (EHR) and systematic assessments of potentially underlying missingness mechanisms are lacking. We aimed to provide a principled approach to empirically characterize missing data processes and investigate performance of analytic methods.

Methods: Three empirical sub-cohorts of diabetic SGLT2 or DPP4-inhibitor initiators with complete information on HbA1c, BMI and smoking as confounders of interest (COI) formed the basis of data simulation under a plasmode framework.

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Purpose: Our objective is to describe how the U.S. Food and Drug Administration (FDA)'s Sentinel System implements best practices to ensure trust in drug safety studies using real-world data from disparate sources.

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  • Researchers faced challenges in using claims data for studying bariatric surgery because they often didn't have body mass index (BMI) measurements.
  • They created a new scoring system, called B3S3, using machine learning to predict pre-operative BMI based on claims data and health records from patients who had bariatric surgery.
  • The B3S3 scoring system performed really well in testing and is a helpful tool for researchers to better understand the effects of obesity on bariatric surgery outcomes.
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  • Lasso regression is a common method for estimating propensity scores in large healthcare studies, but undersmoothing can lead to improved confounding control while risking non-overlap in covariate distributions.
  • The study explores how to choose the right level of undersmoothing for Lasso PS models using simulations and a technique called collaborative-controlled targeted learning.
  • Findings indicate that this approach can effectively reduce bias in treatment effect estimates and highlight the importance of cross-fitting to maintain covariate overlap when using undersmoothed models.
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Objectives: Partially observed confounder data pose a major challenge in statistical analyses aimed to inform causal inference using electronic health records (EHRs). While analytic approaches such as imputation are available, assumptions on underlying missingness patterns and mechanisms must be verified. We aimed to develop a toolkit to streamline missing data diagnostics to guide choice of analytic approaches based on meeting necessary assumptions.

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Objectives: Automated phenotyping algorithms can reduce development time and operator dependence compared to manually developed algorithms. One such approach, PheNorm, has performed well for identifying chronic health conditions, but its performance for acute conditions is largely unknown. Herein, we implement and evaluate PheNorm applied to symptomatic COVID-19 disease to investigate its potential feasibility for rapid phenotyping of acute health conditions.

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Biological plausibility suggests that fluoroquinolones may lead to mitral valve regurgitation or aortic valve regurgitation (MR/AR) through a collagen degradation pathway. However, available real-world studies were limited and yielded inconsistent findings. We estimated the risk of MR/AR associated with fluoroquinolones compared with other antibiotics with similar indications in a population-based cohort study.

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Background And Aims: Immunosuppressed individuals are at higher risk for COVID-19 complications, yet data in patients with inflammatory bowel disease (IBD) are limited. We evaluated the risk of COVID-19- severe sequelae by medication utilization in a large cohort of patients with IBD.

Methods: We conducted a retrospective cohort study utilizing insurance claims data between August 31, 2019, and August 31, 2021.

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Missing data complicates statistical analyses in multi-site studies, especially when it is not feasible to centrally pool individual-level data across sites. We combined meta-analysis with within-site multiple imputation for one-step estimation of the average causal effect (ACE) of a target population comprised of all individuals from all data-contributing sites within a multi-site distributed data network, without the need for sharing individual-level data to handle missing data. We considered two orders of combination and three choices of weights for meta-analysis, resulting in six approaches.

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Purpose: While much has been written about how distributed networks address internal validity, external validity is rarely discussed. We aimed to define key terms related to external validity, discuss how they relate to distributed networks, and identify how three networks (the US Food and Drug Administration's Sentinel System, the Canadian Network for Observational Drug Effect Studies [CNODES], and the National Patient Centered Clinical Research Network [PCORnet]) deal with external validity.

Methods: We define external validity, target populations, target validity, generalizability, and transportability and describe how each relates to distributed networks.

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  • The first follow-on insulin product, Basaglar, was approved in the U.S. in 2015, but information on its use and health outcomes compared to the original insulin glargine (Lantus) is limited.
  • A study analyzed healthcare claims data from a large network to assess the demographics, clinical characteristics, and adverse events among users of both Basaglar and Lantus from 2011 to 2021, identifying over 500,000 users of Lantus and around 63,200 users of Basaglar.
  • The study found a significant increase in Basaglar use from 8.2% in 2017 to 24.8% in 2020, with
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Background: Antitumor necrosis factor (anti-TNF) inhibitors are first-line treatment among patients with ulcerative colitis (UC). With time, patients tend to lose response or become intolerant, necessitating switching to small cell biologics such as tofacitinib or vedolizumab. In this real-world study of a large, geographically diverse US population of TNF-experienced patients with UC, we evaluated the effectiveness and safety of newly initiating treatment with tofacitinib vs vedolizumab.

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Background And Objectives: The use of over-the-counter laxatives is common in the general population. The microbiome-gut-brain axis hypothesis suggests that the use of laxatives could be associated with dementia. We aimed to examine the association between the regular use of laxatives and the incidence of dementia in UK Biobank participants.

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