Leveraging Contextual Information in Extracting Long Distance Relations from Clinical Notes.

Relation extraction from biomedical text is important for clinical decision support applications. In post-marketing pharmacovigilance, for example, Adverse Drug Events (ADE) relate medical problems to the drugs that caused them and were the focus of two recent shared challenges. While good results were reported, there was a room for improvement. Here, we studied two new improved methods for relation extraction: (1) State-of-the-art deep learning contextual representation model called BERT, Bidirectional Encoder Representations from Transformers; (2) Selection of negative training samples based on the "near-miss" hypothesis (the Edge sampling). We used the datasets from MADE and N2C2 Task-2 for performance evaluation. BERT and Edge together improved performance of ADE and Reason (indication) relations extraction by 6.4-6.7 absolute percentage (and error rate reduction of 24%-28%). ADE and Reason relations contained longer text between the entities, which BERT and Edge were able to leverage to achieve the performance improvement. While the performance improvement for medication attribute relations was smaller in absolute percentages, error rate reduction was still considerable.