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The TimeAlign plugin for i2b2 is a visual analysis tool for temporal categorical data from for multiple patient records. It visualizes multiple patients' medical history. Each history contains a set of relevant categorical events (ex. diagnosis, prescription, intervention, room change, admission, discharge, etc). TimeAlign displays the records and their events in a linear, zoomable timeline that allows investigators to quickly grasp the temporal relationships of important events.

TimeAlign lets investigators explore the data via its simple but powerful interaction mechanisms. At the heart is the Align-Rank-Filter (ARF) framework. Investigators can align all patients by some an important first occurrence of an event and discover how other events are related to it. For example, by aligning patients by their first heparin injectionexposure, investigators can examine if the event of low-platelet reading occur more frequently as a potential signal for heparin-induced thrombocytopenia. Ranking, for example, can reorder order patients by the number of low-platelet reading events from highest to lowest. Finally, filtering lets investigators to narrow down patient population by event characteristics: show only patients with at least three exposures of heparin (filter by event count), or show patients who have never had a surgical procedure followed by heparin exposure followed by low-platelet count (filter by an event orderingsequence).

In addition, distribution of events over time can be shown. Groups of patients can be created via filtering. Distribution of groups can be compared. All these features let investigators visualize and interact with the data, explore potentially interesting temporal relationships, formulate hypotheses, and hopefully discover new findings.

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