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Discoveries from Clinical Data

Large database collections of clinical data -- from longitudinal research projects, electronic medical records, and health information exchanges -- provide opportunities to examine controversial findings from smaller scale clinical studies and to conduct retrospective epidemiological studies in areas that lack clinical trials.

NLM established a goal to integrate biomedical, clinical, and public health information systems that promote scientific discovery and speed the translation of research into practice (NLM Long Range Plan, 2006-2016, Goal 3).  One of NLM's key recommendations to fulfill this goal is to "develop linked databases for discovering relationships between clinical data, genetic information, and environmental factors."

LHNCBC's biostatistician and clinicians are using MIT’s large longitudinal MIMIC-II database (33,000 patients with 40,000 intensive care unit (ICU) visits and 180 million rows of data) to answer clinical research questions. We also contributed standard clinical vocabulary code mappings to the latest MIMIC-II release (v 2.6).

We have completed a study on the impact of obesity on outcomes after critical illness, which was published in the journal Critical Care.

Ongoing studies include: 1) the relationship between vitamin B12 levels and mortality; and 2) the relationship between blood transfusions, feeds, and necrotizing enterocolitis (NEC) in newborns.

We developed and implemented Natural Language Processing algorithms to extract patients’ smoking status and discharge destinations from the MIMIC-II physician discharge summaries. We extracted information on episodes of neonatal apnea and bradycardia as well as maternal history from clinical notes for infants in the neonatal intensive care unit (NICU) for the NEC study. We also extracted data about hypertension and hypertensive medications from free-text notes, and used that data to compare to ICD-9 hypertension diagnosis codes in order to evaluate underreporting of certain common conditions after ICU admission.

To assist with integrating and analyzing the data, LHNCBC's researchers are using NLM-supported clinical vocabulary standards to improve the utility of the MIMIC-II database. We mapped the laboratory tests and medications to LOINC and RxNorm, respectively, and its radiology reports to the LOINC codes that describe the radiology study.

We are also developing the Maximum Likelihood (ML) statistical method -- to address measurement error in NLP-derived variables in order to reduce bias -- which could potentially increase the utility of NLP-derived data.

This LHNCBC research aligns closely with NIH's Big Data to Knowledge (BD2K) initiative, which "seeks to facilitate broad use of biomedical big data through new data sharing policies, catalogs of datasets, and enhanced training for early career scientists entering the new world of big data" by supporting "the management, analysis and integration of large-scale data and informatics."

Publications/Tools: 
Callaghan F, Jackson MT, Demner-Fushman D, Abhyankar S, McDonald C. Analysis of data that has been extracted from free-text using natural language processing: a likelihood model for misclassification with an application to medical informatics. International Conference on Advances in Interdisciplinary Statistics and Combinatorics (AISC2012), Greensboro, NC, October 2012
Callaghan F, Jackson MT, Demner-Fushman D, Abhyankar S, McDonald CJ. NLP-derived information improves the estimates of risk of disease compared to estimates based on manually extracted data alone. 5th International Symposium on Semantic Mining in Biomedicine (SMBM 2012), 2012 Sept 3-4, Zurich, Switzerland.
Abhyankar S, Demner-Fushman D, McDonald CJ. Standardizing clinical laboratory data for secondary use. J Biomed Inform. 2012 Aug;45(4):642-50. doi: 10.1016/j.jbi.2012.04.012. Epub 2012 May 3.
Demner-Fushman D, Abhyankar S. Syntactic-semantic frames for clinical cohort identification queries. Data Integration in the Life Sciences (DILS) June 2012, LNBI 7348 proceedings. Lecture Notes in Computer Science. 2012;7348:100-112
Demner-Fushman D, Abhyankar S. Syntactic-semantic question frames for cohort identification. The 2012 Joint Summits on Translational Science. San Francisco, CA. March 2012.
Cameron D, Kavuluru R, Bodenreider O, Mendes PN, Sheth AP, Thirunarayan K. Semantic predications for complex information needs in biomedical literature BIBM 2011:512-519.
Demner-Fushman D, Abhyankar S, Callaghan FM, McDonald CJ. Extracting sources of admission and discharge destinations from discharge summaries [Poster]. AMIA 2011 Fall Symposium.
Callaghan F, Demner-Fushman D, Abhyankar S, McDonald CJ. Addressing errors in a retrospective observational ICU database [poster]. AMIA 2011 Fall Symposium.
Abhyankar S, Callaghan FM, Demner-Fushman D, McDonald CJ. Using informatics tools to study obesity and outcomes after critical illness. NLM Informatics Training Conference 2011, National Institutes of Health (NIH) Campus, Natcher Conference Center, Bethesda, MD, June 28-30, 2011.
Overby CL, Tarczy-Hornoch P, Demner-Fushman D. The potential for automated question answering in the context of genomic medicine: An assessment of existing resources and properties of answers Summit on Translat Bioinforma. 2009 Mar 1;2009:1-25.

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