Data Driven Information Extraction from Chinese Electronic Medical Records
Objective This study aims to propose a data driven framework that takes unstructured free text narratives in Chinese Electronic Medical Records (EMRs) as input and converts them into structured time event description triples, where the description is either an elaboration or an outcome of the medical event. Materials and Methods Our framework uses a hybrid approach. It consists of constructing cross domain core medical lexica, an unsupervised, iterative algorithm to accrue more accurate terms into the lexica, rules to address Chinese writing conventions and temporal descriptors, and a Support Vector Machine (SVM) algorithm that innovatively utilizes Normalized Google Distance (NGD) to estimate the correlation between medical events and their descriptions. Results The effectiveness of the framework was demonstrated with a dataset of 24,817 de identified Chinese EMRs. The cross domain medical lexica were capable of recognizing terms with an F1 score of 0.896. 98.5% of recorded medical events were linked to temporal descriptors. The NGD SVM description event matching achieved an F1 score of 0.874. The end to end time event description extraction of our framework achieved an F1 score of 0.846. Discussion In terms of named entity recognition, the proposed framework outperforms state of the art supervised learning algorithms (F1 score: 0.896 vs. 0.886) In event description association, the NGD SVM is superior to SVM using only local context and semantic features (F1 score: 0.874 vs. 0.838) Conclusions The framework is data driven, weakly supervised, and robust against the variations and noises that tend to occur in a large corpus. It addresses Chinese medical writing conventions and variations in writing styles through patterns used for discovering new terms and rules for updating the lexica.
PloS one