Development Of A Dynamic Prediction Model For Unplanned Icu Admission And Mortality In Hospitalized Patients
Davide Placido, Hans-Christian Thorsen-Meyer, Benjamin Skov Kaas-Hansen, Roc Reguant, Søren Brunak
Frequent assessment of the severity of illness for hospitalized patients is essential in clinical settings to prevent outcomes such as in-hospital mortality and unplanned admission to the intensive care unit (ICU). Classical severity scores have been developed typically using relatively few patient features. Recently, deep learning-based models demonstrated better individualized risk assessments compared to classic risk scores, thanks to the use of aggregated and more heterogeneous data sources for dynamic risk prediction. We investigated to what extent deep learning methods can capture patterns of longitudinal change in health status using time-stamped data from electronic health records. We developed a deep learning model based on embedded text from multiple data sources and recurrent neural networks to predict the risk of the composite outcome of unplanned ICU transfer and in-hospital death. The risk was assessed at regular intervals during the admission for different prediction windows. Input data included medical history, biochemical measurements, and clinical notes from a total of 852,620 patients admitted to non-intensive care units in 12 hospitals in Denmark’s Capital Region and Region Zealand during 2011–2016 (with a total of 2,241,849 admissions)
Evidence-based medicine is at the foundation of the clinical decision process: doctors must continuously take decisions using their knowledge to provide the best care to the patients. For this reason, numerous scores are used in healthcare to support clinicians with decision-making. Such scores vary depending on the target population and the intended use, therefore each medical specialty has its own examples (e.g. in the ICU, APACHE  and SAPS  scores are commonly used to assess severity of illness).
In general departments, Early Warning Scores (EWSs) are used to assess the health status of hospitalized patients. The first EWS was based solely on five physiological parameters, and was later updated by adaptations and improvements [3,4]. VitalPAC was one such early warning score (ViEWS), for which modifications were introduced . These modifications were based on clinicians’ knowledge about the relationship between physiological data and adverse clinical outcomes. Further modifications were implemented in the national early warning score, NEWS, currently being the most used in the Capital Region of Denmark .
Materials and method
This paper adheres to relevant items in the Transparent Reporting of a multivariable prediction model for Individual Prognosis or Diagnosis statement (TRIPOD) (S4 Table) .
The model was trained on 682,041 unique patients and 1,791,705 admissions and evaluated on 170,579 patients and 450,144 admissions as described in Methods (S3 Table). In both parts, 1.5% of the admissions resulted in in-hospital mortality and 0.7% in ICU transfer. 2,583 tokens from the ICD code data type (medical history), 2,421 tokens from the biochemical measurements and 403,869 tokens from the medical notes were used as input. We investigated the inclusion of each data type separately as well as jointly in the same model.
When we explored how the prediction window and assessment rate affect the performances, the most performant model based on the AUPRC was the one trained on all the data sources using a prediction window of 14 days and an assessment rate of 6 hours with an AUROC of 0.904 [0.903–0.904] and AUPRC 0.285 [0.283–0.286] (Fig 4, Table 2). This model was after isotonic recalibration well-calibrated (Fig 4C, S5 Fig) with a calibration slope of 0.964 [0.951, 0.98], an intercept of 0.002 [0.001–0.003] and an upper bound risk of 79%. A full list of precision, recall and specificity for the different models is in the Supplementary (S2 Table).
The main aim of this study was to explore whether data types registered routinely in general departments are predictive of clinical deterioration, ultimately to assess if these suffice for this task. A solution based on data collected routinely might circumvent a common weakness of EWS, i.e. they depend on data that require clinical engagement (e.g., vital signs). Consequently, offering a viable alternative for risk stratification with minimum additional manual data collection effort is preferable.
Exploiting the combined power of entity embedding of tokens from electronic health records and the ability of recurrent neural networks to learn temporal patterns from such data, we built a performant (AUROC and AUPRC up to 0.90 and 0.29, respectively) and well-calibrated deep learning model for predicting the risk of clinical deterioration. Specifically, leveraging medical history data (up to 40 years) from a national register along with in-hospital biochemical data and clinical notes, we trained the model dynamically, meaning that the same model can handle different time points for the same admission.
Combining entity embeddings and recurrent neural networks, we built a highly performant model that every 6 hours during any admission flags patients at higher risk of developing clinical deterioration in the 14 days after the assessment. The model was developed and evaluated using training and validation data, in addition to holdout EHR test data not used during development. A proper prospective evaluation would be needed to establish whether its deployment will produce real-world benefits to patients on hard endpoints. Once clinical utility has been established by trials, the model could both help intervene earlier in patients likely to deteriorate and enrich other clinical trials seeking to identify such early interventions.
Citation: Placido D, Thorsen-Meyer H-C, Kaas-Hansen BS, Reguant R, Brunak S (2023) Development of a dynamic prediction model for unplanned ICU admission and mortality in hospitalized patients. PLOS Digit Health 2(6): e0000116. https://doi.org/10.1371/journal.pdig.0000116
Editor: Jessica Keim-Malpass, University of Virginia, UNITED STATES
Received: August 25, 2022; Accepted: April 24, 2023; Published: June 9, 2023
Copyright: © 2023 Placido et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: The software is available online at https://github.com/daplaci/ClinicalDeteriorationNet. The authors do not have permission to share the data directly; following ethical approval data can be made available for use in secure, dedicated environments via application to the Danish Regions and the Danish Health Data Authority. Researchers wanting access to the data and to use them for research will be required to meet research credentialing requirements. This study was approved by the Danish Patient Safety Authority (3-3013-1731 and 3–3013–1723), the Danish Data Protection Agency (DT SUND 2016–48, 2016–50, 2017–57 and UCPH 514-0255/18-3000:) and the Danish Health Data Authority (FSEID 00003092, FSEID 00003724, FSEID 00004758 and FSEID 00005191).
Funding: We would like to acknowledge the Novo Nordisk Foundation (grants NNF17OC0027594 and NNF14CC0001) and the Danish Innovation Fund (5153-00002B) which supported this study. These foundations contributed to the financing of salaries for SB, DP, RR. BSK-H acknowledges funding from “Grosserer Jakob Ehrenreich og Hustru Grete Ehrenreichs Fond”. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: SB has ownership in Intomics A/S, Hoba Therapeutics Aps, Novo Nordisk A/S, Lundbeck A/S, ALK Abello and managing board memberships in Proscion A/S and Intomics A/S.