title: "Big data" and the electronic health record.
abstract: OBJECTIVE
  Implementation of Electronic Health Record (EHR) systems continues to expand. The massive number of patient encounters results in high amounts of stored data. Transforming clinical data into knowledge to improve patient care has been the goal of biomedical informatics professionals for many decades, and this work is now increasingly recognized outside our field. In reviewing the literature for the past three years, we focus on "big data" in the context of EHR systems and we report on some examples of how secondary use of data has been put into practice.
  
  
  METHODS
  We searched PubMed database for articles from January 1, 2011 to November 1, 2013. We initiated the search with keywords related to "big data" and EHR. We identified relevant articles and additional keywords from the retrieved articles were added. Based on the new keywords, more articles were retrieved and we manually narrowed down the set utilizing predefined inclusion and exclusion criteria.
  
  
  RESULTS
  Our final review includes articles categorized into the themes of data mining (pharmacovigilance, phenotyping, natural language processing), data application and integration (clinical decision support, personal monitoring, social media), and privacy and security.
  
  
  CONCLUSIONS
  The increasing adoption of EHR systems worldwide makes it possible to capture large amounts of clinical data. There is an increasing number of articles addressing the theme of "big data", and the concepts associated with these articles vary. The next step is to transform healthcare big data into actionable knowledge.
authors.affiliation: Lucila Ohno-Machado, Division of Biomedical Informatics, 9500 Gilman Drive, MC 0505, La Jolla, California, 92037-0505, USA, Tel: +1 858 822 4931, E-mail: machado@ucsd.edu.
authors.forename: M K
authors.initials: MK
authors.lastname: Ross
authors.forename: W
authors.initials: W
authors.lastname: Wei
authors.forename: L
authors.initials: L
authors.lastname: Ohno-Machado
mesh_terms: D019295:Computational Biology; D057225:Data Mining; D020000:Decision Support Systems, Clinical; D057286:Electronic Health Records; D016347:Medical Records Systems, Computerized; D009323:Natural Language Processing; D060735:Pharmacovigilance; D061108:Social Media
keywords: Electronic health records; data mining; natural language processing; privacy; quality improvement; security