Abbreviations are common in clinical documentation, as this type of text is written under time-pressure and serves mostly for internal communication. This study attempts to apply and extend existing rule-based algorithms that have been developed for English and Swedish abbreviation detection, in order to create an abbreviation detection algorithm for Swedish clinical texts that can identify and suggest definitions for abbreviations and acronyms. This can be used as a pre-processing step for further information extraction and text mining models, as well as for readability solutions. Through a literature review, a number of heuristics were defined for automatic abbreviation detection. These were used in the construction of the Swedish Clinical Abbreviation Normalizer (SCAN). The heuristics were: a) freely available external resources: a dictionary of general Swedish, a dictionary of medical terms and a dictionary of known Swedish medical abbreviations, b) maximum word lengths (from three to eight characters), and c) heuristics for handling common patterns such as hyphenation. For each token in the text, the algorithm checks whether it is a known word in one of the lexicons, and whether it fulfills the criteria for word length and the created heuristics. The final algorithm was evaluated on a set of 300 Swedish clinical notes from an emergency department at the Karolinska University Hospital, Stockholm. These notes were annotated for abbreviations, a total of 2,050 tokens. This set was annotated by a physician accustomed to reading and writing medical records. The algorithm was tested in different variants, where the word lists were modified, heuristics adapted to characteristics found in the texts, and different combinations of word lengths. The best performing version of the algorithm achieved an F-Measure score of 79%, with 76% recall and 81% precision, which is a considerable improvement over the baseline where each token was only matched against the word lists (51% F-measure, 87% recall, 36% precision). Not surprisingly, precision results are higher when the maximum word length is set to the lowest (three), and recall results higher when it is set to the highest (eight). Algorithms for rule-based systems, mainly developed for English, can be successfully adapted for abbreviation detection in Swedish medical records. System performance relies heavily on the quality of the external resources, as well as on the created heuristics. In order to improve results, part-of-speech information and/or local context is needed for disambiguation. In the case of Swedish, compounding also needs to be handled.

The aim of the thesis is to investigate the feasibility of using text mining methods to reconstruct patient journeys from unstructured clinical narratives. A novel method to extract and represent patient journeys is proposed and evaluated in this thesis. A composition of methods were designed, developed and evaluated to this end; which included health-related concept extraction, temporal information extraction, and concept clustering and automated work-flow generation. A suite of methods to extract clinical information from healthcare narratives were proposed and evaluated in order to enable chronological ordering of clinical concepts. Specifically, we proposed and evaluated a data-driven method to identify key clinical events (i.e., medical problems, treatments, and tests) using a sequence labelling algorithm, CRF, with a combination of lexical and syntactic features, and a rule-based post-processing method including label correction, boundary adjustment and false positive filter. The method was evaluated as part of the 2012 i2b2 challengeand achieved a state-of-the-art performance with a strict and lenient micro F1-measure of 83.45% and 91.13% respectively. A method to extract temporal expressions using a hybrid knowledge- (dictionary and rules) and data-driven (CRF) has been proposed and evaluated. The method demonstrated the state-of-the-art performance at the 2012 i2b2 challenge: F1-measure of 90.48% and accuracy of 70.44% for identification and normalisation respectively. For temporal ordering of events we proposed and evaluated a knowledge-driven method, with a F1-measure of 62.96% (considering the reduced temporal graph) or 70.22% for extraction of temporal links. The method developed consisted of initial rule-based identification and classification components which utilised contextual lexico-syntactic cues for inter-sentence links, string similarity for co-reference links, and subsequently a temporal closure component to calculate transitive relations of the extracted links. In a case study of survivors of childhood central nervous system tumours (medulloblastoma), qualitative evaluation showed that we were able to capture specific trends part of patient journeys. An overall quantitative evaluation score (average precision and recall) of 94-100% for individual and 97% for aggregated patient journeys were also achieved. Hence, indicating that text mining methods can be used to identify, extract and temporally organise key clinical concepts that make up a patient’s journey. We also presented an analyses of healthcare narratives, specifically exploring the content of clinical and patient narratives by using methods developed to extract patient journeys. We found that health-related quality of life concepts are more common in patient narrative, while clinical concepts (e.g., medical problems, treatments, tests) are more prevalent in clinical narratives. In addition, while both aggregated sets of narratives contain all investigated concepts; clinical narratives contain, proportionally, more health-related quality of life concepts than clinical concepts found in patient narratives. These results demonstrate that automated concept extraction, in particular health-related quality of life, as part of standard clinical practice is feasible. The proposed method presented herein demonstrated that text mining methods can be efficiently used to identify, extract and temporally organise key clinical concepts that make up a patient’s journey in a healthcare system. Automated reconstruction of patient journeys can potentially be of value for clinical practitioners and researchers, to aid large scale analyses of implemented care pathways, and subsequently help monitor, compare, develop and adjust clinical guidelines both in the areas of chronic diseases where there is plenty of data and rare conditions where potentially there are no established guidelines.

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Information contained in the free text of health records is useful for the immediate care of patients as well as for medical knowledge creation. Advances in clinical language processing have made it possible to automatically extract this information, but most research has, until recently, been conducted on clinical text written in English. In this thesis, however, information extraction from Swedish clinical corpora is explored, particularly focusing on the extraction of clinical findings. Unlike most previous studies, Clinical Finding was divided into the two more granular sub-categories Finding (symptom/result of a medical examination) and Disorder (condition with an underlying pathological process). For detecting clinical findings mentioned in Swedish health record text, a machine learning model, trained on a corpus of manually annotated text, achieved results in line with the obtained inter-annotator agreement figures. The machine learning approach clearly outperformed an approach based on vocabulary mapping, showing that Swedish medical vocabularies are not extensive enough for the purpose of high-quality information extraction from clinical text. A rule and cue vocabulary-based approach was, however, successful for negation and uncertainty classification of detected clinical findings. Methods for facilitating expansion of medical vocabulary resources are particularly important for Swedish and other languages with less extensive vocabulary resources. The possibility of using distributional semantics, in the form of Random indexing, for semi-automatic vocabulary expansion of medical vocabularies was, therefore, evaluated. Distributional semantics does not require that terms or abbreviations are explicitly defined in the text, and it is, thereby, a method suitable for clinical corpora. Random indexing was shown useful for extending vocabularies with medical terms, as well as for extracting medical synonyms and abbreviation dictionaries.