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Revista médica de Chile

Print version ISSN 0034-9887


VILLENA, Fabián  and  DUNSTAN, Jocelyn. Automatic keyword retrieval from clinical texts: an application of natural language processing to massive data of Chilean suspected diagnosis. Rev. méd. Chile [online]. 2019, vol.147, n.10, pp.1229-1238. ISSN 0034-9887.


Free-text imposes a challenge in health data analysis since the lack of structure makes the extraction and integration of information difficult, particularly in the case of massive data. An appropriate machine-interpretation of electronic health records in Chile can unleash knowledge contained in large volumes of clinical texts, expanding clinical management and national research capabilities.


To illustrate the use of a weighted frequency algorithm to find keywords. This finding was carried out in the diagnostic suspicion field of the Chilean specialty consultation waiting list, for diseases not covered by the Chilean Explicit Health Guarantees plan.

Material and Methods:

The waiting lists for a first specialty consultation for the period 2008-2018 were obtained from 17 out of 29 Chilean health services, and total of 2,592,925 diagnostic suspicions were identified. A natural language processing technique called Term Frequency–Inverse Document Frequency was used for the retrieval of diagnostic suspicion keywords.


For each specialty, four key words with the highest weighted frequency were determined. Word clouds showing words weighted by their importance were created to obtain a visual representation. These are available at


The algorithm allowed to summarize unstructured clinical free-text data, improving its usefulness and accessibility.

Keywords : Data Mining; Information Storage and Retrieval; Machine Learning; Medical Informatics; Natural Language Processing.

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