Active Learning for Concept Extraction from Clinical Free Text

Abstract

An increasing volume of clinical free-text data, such as discharge summaries and progress reports, has been collected by hospitals and healthcare centres and stored electronically for further processing. Extracting structured clinical information from such unstructured text resources is necessary for enabling secondary usage of reports, such as reporting, reasoning and retrieving, and for further processing in down-stream eHealth workflows. However, this analysis cannot be done manually, due to the high cost incurred by qualified experts to annotate the clinical free text. A significant initial step in extracting information from clinical free text is concept extraction, which involves identifying entities of interest in the clinical domain (such as diseases, medications, and symptoms). Currently, supervised machine learning approaches effectively extract clinical concepts by building powerful statistical models. However, these approaches require a large amount of high quality, annotated train data, which is created manually by domain experts through a costly and timeconsuming process. This results in a robust active learning framework for extracting clinical concepts, using state-of-the-art, active learning approaches. The second step is to leverage clinical information resources (i.e., terminologies and clinical information extraction tools) and other machine learning approaches (i.e., semi-supervised learning, unsupervised learning, and representation learning) to develop domain-specific and generic active learning approaches. This leads to a number of novel, active learning query strategies and a seed selection approach that outperform the state-of-the-art approaches with less manual annotation effort. The last step is to validate the benefits of the developed AL-based framework in reducing the annotation cost (i.e., time) through a comprehensive user study. An AL-assisted pre-annotation scheme is also introduced, in which the learning models built across the AL process generate high quality pre-annotations to be reviewed by human annotators. This further accelerates the annotation process, by significantly reducing the number of manual annotations that must be added or corrected compared to de novo annotation.The results of this study demonstrate that AL plays an important role in reducing the manual annotation cost. The CEAL framework extracts high quality domain concepts from clinical narratives, while significantly reducing the labour cost with up to 35% less annotation time required. Additionally, AL-assisted preannotations accelerate the de novo annotation process with a further 20% less annotation time required. This thesis contributes to information extraction from clinical unstructured text resources by alleviating the burden of manual annotation.The practical significance of this research is three-fold: (1) benefitting the overall patient healthcare by facilitating downstream eHealth workflows such as supporting clinical information processing, reporting, reasoning, and efficient decision m...

A Comparative Analysis of Active Learning for Biomedical Text Mining

“…Using crowdsourcing 60 for labelling clinical data is not useful in the general domain; manual labelling is an ex-61 pensive and labour-intensive task. 62 AL [15] and semi-supervised learning [16] are viable options in contrast to standard 63 supervised ML methods and can reduce labelling costs. AL can prepare to accomplish an 64 automated system with high adequacy and less labelling cost.…”