  Objective: In this paper, we develop a personalized real-time risk scoring
algorithm that provides timely and granular assessments for the clinical acuity
of ward patients based on their (temporal) lab tests and vital signs; the
proposed risk scoring system ensures timely intensive care unit (ICU)
admissions for clinically deteriorating patients. Methods: The risk scoring
system learns a set of latent patient subtypes from the offline electronic
health record data, and trains a mixture of Gaussian Process (GP) experts,
where each expert models the physiological data streams associated with a
specific patient subtype. Transfer learning techniques are used to learn the
relationship between a patient's latent subtype and her static admission
information (e.g. age, gender, transfer status, ICD-9 codes, etc). Results:
Experiments conducted on data from a heterogeneous cohort of 6,321 patients
admitted to Ronald Reagan UCLA medical center show that our risk score
significantly and consistently outperforms the currently deployed risk scores,
such as the Rothman index, MEWS, APACHE and SOFA scores, in terms of
timeliness, true positive rate (TPR), and positive predictive value (PPV).
Conclusion: Our results reflect the importance of adopting the concepts of
personalized medicine in critical care settings; significant accuracy and
timeliness gains can be achieved by accounting for the patients' heterogeneity.
Significance: The proposed risk scoring methodology can confer huge clinical
and social benefits on more than 200,000 critically ill inpatient who exhibit
cardiac arrests in the US every year.
