Missing covariates are commonly encountered when evaluating covariate effects on survival outcomes. Excluding missing data from the analysis may lead to biased parameter estimation and a misleading conclusion. The inverse probability weighting method is widely used to handle missing covariates. However, obtaining asymptotic variance in frequentist inference is complicated because it involves estimating parameters for propensity scores. In this paper, we propose a new approach based on an approximate Bayesian method without using Taylor expansion to handle missing covariates for survival data. We consider a stratified proportional hazards model so that it can be used for the non-proportional hazards structure. Two cases for missing pattern are studied: a single missing pattern and multiple missing patterns. The proposed estimators are shown to be consistent and asymptotically normal, which matches the frequentist asymptotic properties. Simulation studies show that our proposed estimators are asymptotically unbiased and the credible region obtained from posterior distribution is close to the frequentist confidence interval. The algorithm is straightforward and computationally efficient. We apply the proposed method to a stem cell transplantation data set.
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http://dx.doi.org/10.1007/s10985-021-09542-4 | DOI Listing |
Biometrics
January 2025
MRC Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, CB2 0SR, United Kingdom.
Dynamic treatment regimes (DTRs) formalize medical decision-making as a sequence of rules for different stages, mapping patient-level information to recommended treatments. In practice, estimating an optimal DTR using observational data from electronic medical record (EMR) databases can be complicated by nonignorable missing covariates resulting from informative monitoring of patients. Since complete case analysis can provide consistent estimation of outcome model parameters under the assumption of outcome-independent missingness, Q-learning is a natural approach to accommodating nonignorable missing covariates.
View Article and Find Full Text PDFJ Neurol
January 2025
John Walton Muscular Dystrophy Research Centre, Newcastle University, Newcastle-upon-Tyne, UK.
PROPEL (ATB200-03; NCT03729362) compared the efficacy and safety of cipaglucosidase alfa plus miglustat (cipa + mig), a two-component therapy for late-onset Pompe disease (LOPD), versus alglucosidase alfa plus placebo (alg + pbo). The primary endpoint was change in 6-min walk distance (6MWD) from baseline to week 52. During PROPEL, COVID-19 interrupted some planned study visits and assessment windows, leading to delayed visits, make-up assessments for patients who missed ≥ 3 successive infusions before planned assessments at weeks 38 and 52, and some advanced visits (end-of-study/early-termination visits).
View Article and Find Full Text PDFJ Alzheimers Dis
January 2025
Multimodal Imaging of Neurodegenerative Disease (MIND) Unit, National Institute of Aging, Intramural Research Program, Baltimore, MD, USA.
Background: High-density lipoprotein (HDL) modulates the blood-brain barrier and cerebrovascular integrity, likely influencing the risk of Alzheimer's disease (AD), neurodegeneration, and cognitive decline.
Objective: This study aims to identify HDL protein cargo associated with brain amyloid deposition and brain volume in regions vulnerable to AD pathology in older adults.
Methods: HDL was separated from the plasma of 65 non-demented participants of the Atherosclerosis Risk in Communities (ARIC) study using a fast protein liquid chromatography method.
Differentiated service delivery (DSD) models in resource-limited settings have reduced strain on health services and improved client experience, retention and viral suppression, but little is known about the impact of HIV DSD models on quality of life (QoL), which is essential for optimizing person-centered care. This study assessed the impact of DSD models on QoL, loss to follow-up (LTFU), and mortality among persons living with HIV (PLHIV) on ART over time at a large urban HIV clinic in Uganda. We analyzed records of 1,000 PLHIV who had been on ART for 10 years and followed up for eight years, starting in 2014 or 2015 at the Infectious Diseases Institute clinic in Kampala, Uganda.
View Article and Find Full Text PDFMitochondrial DNA (mtDNA) plays a crucial role in numerous cellular processes, yet its impact on human behavior remains underexplored. The current paper proposes a novel covariance structure model with seven parameters to specifically isolate and quantify mtDNA effects on human behavior. This approach uses extended pedigrees to obtain estimates of mtDNA variance while controlling for other genetic and environmental influences.
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