Use of machine learning to analyse routinely collected intensive care unit data: a systematic review
Open accessAbstract
BACKGROUND: Intensive care units (ICUs) face financial, bed management, and staffing constraints. Detailed data covering all aspects of patients' journeys into and through intensive care are now collected and stored in electronic health records: machine learning has been used to analyse such data in order to provide decision support to clinicians. METHODS: Systematic review of the applications of machine learning to routinely collected ICU data. Web of Science and MEDLINE databases were searched to identify candidate articles: those on image processing were excluded. The study aim, the type of machine learning used, the size of dataset analysed, whether and how the model was validated, and measures of predictive accuracy were extracted. RESULTS: Of 2450 papers identified, 258 fulfilled eligibility criteria. The most common study aims were predicting complications (77 papers [29.8% of studies]), predicting mortality (70 [27.1%]), improving prognostic models (43 [16.7%]), and classifying sub-populations (29 [11.2%]). Median sample size was 488 (IQR 108-4099): 41 studies analysed data on > 10,000 patients. Analyses focused on 169 (65.5%) papers that used machine learning to predict complications, mortality, length of stay, or improvement of health. Predictions were validated in 161 (95.2%) of these studies: the area under the ROC curve (AUC) was reported by 97 (60.2%) but only 10 (6.2%) validated predictions using independent data. The median AUC was 0.83 in studies of 1000-10,000 patients, rising to 0.94 in studies of > 100,000 patients. The most common machine learning methods were neural networks (72 studies [42.6%]), support vector machines (40 [23.7%]), and classification/decision trees (34 [20.1%]). Since 2015 (125 studies [48.4%]), the most common methods were support vector machines (37 studies [29.6%]) and random forests (29 [23.2%]). CONCLUSIONS: The rate of publication of studies using machine learning to analyse routinely collected ICU data is increasing rapidly. The sample sizes used in many published studies are too small to exploit the potential of these methods. Methodological and reporting guidelines are needed, particularly with regard to the choice of method and validation of predictions, to increase confidence in reported findings and aid in translating findings towards routine use in clinical practice.
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Most AI tools remain poorly validated and untested in real settings.
“Despite the need to support overwhelmed ICUs facing staff shortages, increasing case complexity, and rising costs, most AI tools remain poorly validated and untested in real settings. [3, 45]”
From Implementing Artificial Intelligence in Critical Care Medicine: a consensus of 22. (2025) · cites this paper as [3]
The Discussion (Implications) says only a small minority of reviewed ICU machine-learning studies validated algorithms on independent data, and that studies rarely discussed implementation or whether the algorithms improved care. This supports concerns about validation, but the review concerns ICU machine-learning studies rather than most AI tools generally; rarely discussing implementation does not establish that the tools were untested in real settings. (LLM, conf=0.85)
Experimental — accuracy not yet measuredAUROC is widely adopted for binary classification in ICU prediction tasks and offers threshold-independent evaluation, enabling fair comparison across hospitals without requiring model calibration.
“AUROC is widely adopted for binary classification in ICU prediction tasks [12, 75] and offers threshold-independent evaluation, enabling fair comparison across hospitals without requiring model calibration.”
From Toward generalizable and interpretable machine learning models in healthcare: Insights from ICU outcome predictions (2026) · cites this paper as [12]
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- Authors
- Shillan, D., Sterne, J. A. C., Champneys, A., & Gibbison, B.
- Affiliations
- University of Bristol (GB)
- Bristol Royal Infirmary (GB)
- Corresponding author
- Gibbison, Ben
- Venue
- Critical Care
- Published
- 2019-08-22
- Volume
- 23
- Issue
- 1
- Pages
- 284-284
- ISSN
- 1364-8535 (ISSN-L)
- PMC
- PMC6704673
- OpenAlex
- W2969097171
- Cited by
- 251
- References
- 44
- Citations by year
- 2026: 34 · 2025: 47 · 2024: 26 · 2023: 46 · 2022: 44 · 2021: 32 · 2020: 22
- FWCI
- 1.63
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Locations
- Critical Care (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- Explore Bristol Research (publishedVersion, cc-by)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Funders
- National Institute for Health Research (BRC at University of Bristol and UH Bristol NHSFT, BRC at the University of Bristol and UH Bristol NHS FT, BRC at The University of Bristol and UH Bristol NHS FT)
- Topics
- Physical Sciences › Computer Science › Artificial Intelligence › Machine Learning in Healthcare
- Health Sciences › Health Professions › Health Information Management › Artificial Intelligence in Healthcare
- Health Sciences › Medicine › Epidemiology › Sepsis Diagnosis and Treatment
- Keywords
- machine learning, intensive care unit, electronic health records, clinical decision support, mortality prediction, complication prediction, prognostic model, model validation, sample size, random forest, support vector machine, artificial neural networks, length of hospital stay, reporting guidelines, methodological quality, health technology assessment
- MeSH terms
- Machine Learning, Data Analysis, Adult, Female, Humans, Intensive Care Units, Male, Electronic Health Records
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