Our Work

News and Events

1. Dynamic model updating (DMU) approach for statistical learning model building with missing data, Rahi Jain and Wei Xu, BMC Bioinformatics (2021)

2. Mega-and meta-analyses of fecal metagenomic studies in predicting response to immune checkpoint inhibitors, Alya Heirali, Bo Chen, Matthew Wong, Pierre HH Schneeberger, Victor Rey, Anna Spreafico, Wei Xu, Bryan Coburn, Journal of Clinical Oncology (2021)

3. Lisa Avery, presented an informative talk on the use of "Report Rx package" in the Knowledge Translation Committee meeting, May 2021

4. Dr. Osvaldo Espin Garcia has joined as an Assistant Professor at Dalla Lana School of Public Health, UoT. Congratulations Osvaldo!

 BMC Bioinformatics (2021)

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Dynamic model updating (DMU) approach for statistical learning model building with missing data

                                Rahi Jain & Wei Xu 

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Abstract

Developing statistical and machine learning methods on studies with missing information is a ubiquitous challenge in real-world biological research. The strategy in literature relies on either removing the samples with missing values like complete case analysis (CCA) or imputing the information in the samples with missing values like predictive mean matching (PMM) such as MICE. Some limitations of these strategies are information loss and closeness of the imputed values with the missing values. Further, in scenarios with piecemeal medical data, these strategies have to wait to complete the data collection process to provide a complete dataset for statistical models.

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PLOS One (2020)

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Predictive analysis methods for human microbiome data with application to Parkinson’s disease

Mei Dong , Longhai Li, Man Chen, Anthony Kusalik, Wei Xu

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Abstract

Microbiome data consists of operational taxonomic unit (OTU) counts characterized by zero-inflation, over-dispersion, and grouping structure among samples. Currently, statistical testing methods are commonly performed to identify OTUs that are associated with a phenotype. The limitations of statistical testing methods include that the validity of p-values/q-values depend sensitively on the correctness of models and that the statistical significance does not necessarily imply predictivity. Predictive analysis using methods such as LASSO is an alternative approach for identifying associated OTUs and for measuring the predictability of the phenotype variable with OTUs and other covariate variables. We investigate three strategies of performing predictive analysis: (1) LASSO: fitting a LASSO multinomial logistic regression model to all OTU counts with specific transformation; (2) screening+GLM: screening OTUs with q-values returned by fitting a GLMM to each OTU, then fitting a GLM model using a subset of selected OTUs; (3) screening+LASSO: fitting a LASSO to a subset of OTUs selected with GLMM. We have conducted empirical studies using three simulation datasets generated using Dirichlet-multinomial models and a real gut microbiome data related to Parkinson’s disease to investigate the performance of the three strategies for predictive analysis. Our simulation studies show that the predictive performance of LASSO with appropriate variable transformation works remarkably well on zero-inflated data. Our results of real data analysis show that Parkinson’s disease can be predicted based on selected OTUs after the binary transformation, age, and sex with high accuracy (Error Rate = 0.199, AUC = 0.872, AUPRC = 0.912). These results provide strong evidences of the relationship between Parkinson’s disease and the gut microbiome.