In this paper, we present a method to dynamically predict the failure of physiological subsystems from patients admitted to the Intensive Care Unit (ICU) using heterogeneous data. We model the probability of failure in each subsystem as a latent state that evolves over time. We propose a method using Generalized Linear Dynamic models to model this latent state which is updated each time new patient data is observed. Then, we estimate the probability of patient mortality as a combination of the estimated probability of failure for different physiological subsystems. We use noun phrase extraction and statistical Topic Models to extract discriminative features which capture the patient health context that can not be obtained when only numerical features are used. We proposed a method of imputing missing values using the non-ignorable nature of the patient data. We test our proposed approach using 15,000 Electronic Medical Records (EMRs) obtained from the MIMIC II public dataset. Experimental results show that the proposed model allows us to predict subsystem failure and mortality probability with high sensitivity and specificity and detect an increase in the probability of mortality.

In this paper, we present a method to dynamically estimate the probability of mortality inside the Intensive Care Unit (ICU) by combining heterogeneous data. We propose a method based on Generalized Linear Dynamic Models that models the probability of mortality as a latent state that evolves over time. This framework allows us to combine different types of features (lab results, vital signs readings, doctor and nurse notes, etc) into a single state, which is updated each time new patient data is observed. In addition, we include the use of text features, based on medical noun phrase extraction and Statistical Topic Models. These features provide context about the patient that cannot be captured when only numerical features are used. We fill out the missing values using a Regularized Expectation Maximization based method assuming temporal data. We test our proposed approach using 15,000 Electronic Medical Records (EMRs) obtained from the MIMIC II public dataset. Experimental results show that the proposed model allows us to detect an increase in the probability of mortality before it occurs. We report an AUC 0.8657. Our proposed model clearly outperforms other methods of the literature in terms of sensitivity with 0.7885 compared to 0.6559 of Naive Bayes and F-score with 0.5929 compared to 0.4662 of Apache III score after 24 hours.

We present a new, robust and computationally efficient Hierarchical Bayesian model for effective topic correlation modeling. We model the prior distribution of topics by a Generalized Dirichlet distribution (GD) rather than a Dirichlet distribution as in Latent Dirichlet Allocation (LDA). We define this model as GD-LDA. This framework captures correlations between topics, as in the Correlated Topic Model (CTM) and Pachinko Allocation Model (PAM), and is faster to infer than CTM and PAM. GD-LDA is effective to avoid over-fitting as the number of topics is increased. As a tree model, it accommodates the most important set of topics in the upper part of the tree based on their probability mass. Thus, GD-LDA provides the ability to choose significant topics effectively. To discover topic relationships, we perform hyper-parameter estimation based on Monte Carlo EM Estimation. We provide results using Empirical Likelihood(EL) in 4 public datasets from TREC and NIPS. Then, we present the performance of GD-LDA in ad hoc information retrieval (IR) based on MAP, [email protected], and Discounted Gain. We discuss an empirical comparison of the fitting time. We demonstrate significant improvement over CTM, LDA, and PAM for EL estimation. For all the IR measures, GD-LDA shows higher performance than LDA, the dominant topic model in IR. All these improvements with a small increase in fitting time than LDA, as opposed to CTM and PAM.

Most of the relevance feedback algorithms only use document terms as feedback (local features) in order to update the query and re-rank the documents to show to the user. This approach is limited by the terms of those documents without any global context. We propose to use statistical topic modeling techniques in relevance feedback to incorporate a better estimate of context by including global information about the document. This is particularly helpful for difficult queries where learning the context from the interactions with the user is crucial. We propose to use the topic mixture information obtained to characterize the documents and learn their topics. Then, we rank documents incorporating positive and negative feedback by fitting a latent distribution for each class of documents online and combining all the features using Bayesian Logistic Regression. We show results using the OHSUMED dataset for 3 different variants and obtain higher performance, up to 12.5% in Mean Average Precision (MAP).