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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta>
      <issn pub-type="ppub">1613-0073</issn>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>AI Solution for Emergency Department Patient Triage</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Georgia Sowerby</string-name>
          <email>georgia.sowerby@york.ac.uk</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Ol'Tunde Ashaolu</string-name>
          <email>tunde.ashaolu@nhs.net</email>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Radu Calinescu</string-name>
          <email>radu.calinescu@york.ac.uk</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Stephen Connor</string-name>
          <email>stephen.connor@york.ac.uk</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Workshop</string-name>
        </contrib>
        <contrib contrib-type="editor">
          <string-name>Istanbul, Turkiye</string-name>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Department of Computer Science, University of York</institution>
          ,
          <addr-line>York</addr-line>
          ,
          <country country="UK">United Kingdom</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Department of Mathematics, University of York</institution>
          ,
          <addr-line>York</addr-line>
          ,
          <country country="UK">United Kingdom</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>York and Scarborough Teaching Hospitals NHS Foundation Trust</institution>
          ,
          <addr-line>Scarborough</addr-line>
          ,
          <country country="UK">United Kingdom</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>Hospital Emergency Departments (EDs) worldwide are overwhelmed. The number of people attending EDs increases yearly; however, there is a shortage of doctors and many unfilled vacancies. Unfortunately, this means waiting times can be very long for patients, and doctors are overworked. This paper summarises a PhD project to develop and integrate two key components of an end-to-end hybrid Artificial Intelligence (AI) solution for ED patient triage, building on an existing system DAISY. The first component involves using formally verified machine learning (ML) models to classify patient characteristics that play a major role in ED triage but are dificult to determine by directly asking patients. The second component is a Bayesian network that takes the predictions of these verified ML models and additional data obtained from the patient (e.g., medical history, current symptoms, and vital signs) and generates an advisory patient triage report supporting the decision-making of ED medical teams.</p>
      </abstract>
      <kwd-group>
        <kwd>Clinical decision support system</kwd>
        <kwd>Bayesian network</kwd>
        <kwd>Rule-based expert system</kwd>
        <kwd>Machine learning</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        Emergency departments worldwide face growing challenges due to increasing demand and limited
resources. In the UK, the National Health Service (NHS) Constitution handbook pledges a maximum
four-hour ED waiting time, with an operational standard that 95% of patients are admitted, transferred,
or discharged within this timeframe [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. Yet in 2022-23, NHS reports show that out of 25 million ED
patients, 30% waited longer than four hours to receive care [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. This highlights strain on the system and
raises concerns about timely and efective care. Furthermore, British Medical Association data reveal a
significant shortage of doctors in England, and many vacant positions [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ].
      </p>
      <p>These challenges are not unique to the UK. The World Health Organisation has reported that many
European countries are facing “substantial shortages and gaps” [4]. The culmination of these pressures
results in a challenging and high-stress working environment for ED staf, many of whom work long
hours and report increasing levels of job dissatisfaction [5].</p>
      <p>A key component in managing ED patient flow is triage, the “clinical process to prioritise patients,
completed before a full assessment to support efective management of demand and flow, identifying time
critical requirements for patients” [6]. This process typically comprises five stages [ 7]:
1. Reception: Administrative staf gather preliminary information by observing the patient and
listening to their concerns. Patients who need immediate care can be escalated at this stage;
2. History and Symptoms: A triage clinician collects detailed patient information, asking questions
otherwise, they progress to the next.</p>
      <p>about their medical history and current symptoms.</p>
      <p>CEUR</p>
      <p>ceur-ws.org
3. Vital Sign Measurement: Often occurring in tandem with the previous stage, the clinician
measures and records the patient’s vital parameters (e.g., temperature, heart rate, respiratory rate,
blood pressure, oxygen saturation).
4. Initial Assessment: The clinician analyses the collected data to determine the patient’s triage
score and suggest potential assessments. This analysis can lead to actions such as escalating the
case, returning the patient to the waiting room, or transferring them to a diferent department.
5. Senior Clinician Review: A senior clinician reviews the collected patient information and
any potential assessments suggested by the clinician from Stage 4, then conducts a physical
examination. They then decide on a treatment plan, which might include treating and discharging,
referring for further investigations, admitting, or transferring to another facility.</p>
      <p>This process is prone to inconsistency, especially during busy periods, and automating it is challenging
as automated triage systems often rely solely on structured data (i.e., medical history, patient-reported
symptoms, and vital signs). In contrast, doctors also use physical examinations and clinical intuition to
assess clinically relevant patient characteristics (i.e., observable signs that indicate a patient’s
condition). Automated systems currently lack sensory input and therefore miss this important information.
However, cameras and microphones can capture visual and auditory cues that may ofer additional
insight into a patient’s condition. Incorporating this data into triage systems could improve diagnostic
accuracy. ML models are well suited to learning such patterns, and formally verifying these models can
help improve confidence in their predictions, which is essential in clinical environments.</p>
      <p>Clinical decision support systems (CDSSs) ofer one possible solution to improve triage consistency
and support overloaded clinicians by helping doctors make fair, evidence-based decisions regarding
patient care. They are classified into knowledge-based or non-knowledge-based [ 8]. Knowledge-based
systems use explicit rules, usually formulated as if-then statements, to represent medical knowledge.
In contrast, non-knowledge based systems use ML techniques to identify patterns from large datasets.
Although increasingly common in research, the real-world use of non-knowledge based CDSSs is limited
due to concerns including explainability and limited access to high-quality data [8]. Knowledge-based
systems are often preferred in clinical environments because their recommendations can be traced
to clear, interpretable rules. However, these systems are deterministic and do not model uncertainty,
which can limit their flexibility when information is incomplete or ambiguous.</p>
      <p>One prototypical example of such systems is DAISY (Diagnostic AI System for Robot-Assisted A&amp;E
Triage) [7, 9, 10, 11], a knowledge-based CDSS developed to support ED triage by automating Stages 2
through 4 of the process outlined earlier. It uses a rule-based architecture that prioritises transparency
and explainability, but it does not model uncertainty or provide probability-ranked outputs.</p>
      <p>To address DAISY’s limitations and to lay the foundation for its next generation, this research proposes
a hybrid CDSS that combines machine learning, probabilistic reasoning, and rule-based logic. The
overarching aim of this research is to employ AI technologies to develop a CDSS that automates Stages
2 − 4 (and possibly part of Stage 5) of ED triage with accurate results, reducing ED patient waiting times
and ED medical staf workload. To that end, the following research questions guide this work:
RQ1 How can a Bayesian network component be used alongside or instead of the current DAISY
rule-based expert system to improve the accuracy of patient triage and assessment?
RQ2 Which patient characteristics relevant to ED triage can be identified with acceptable accuracy
using verified ML?
RQ3 How can the ML classifiers from RQ 2 be integrated with the Bayesian network from RQ1 to
further improve triage and assessment in DAISY?</p>
    </sec>
    <sec id="sec-2">
      <title>2. Related Work</title>
      <p>Many clinical decision support systems have been proposed over the years. One of the earliest and most
influential was INTERNIST-I, developed in the 1970s to address the growing complexity of internal
medicine [12]. At its peak, the INTERNIST-I knowledge base included 572 diagnoses and over 4,000
patient findings, with more than 4,000 rules [ 13]. The rules were written by medical experts using
textbooks and their own experience. However, the system had several limitations: it treated users as
passive, required highly specific terminology for input, and generated consultations that lasted up to 75
minutes, which made it impractical for fast-paced clinical settings such as the ED.</p>
      <p>To address these issues, Quick Medical Reference (QMR) was developed in the early 1980s. Like
INTERNIST-I, QMR used the same knowledge base but acted more as an interactive information tool.
It allowed users to input findings and receive feedback, supported by a completer feature to improve
usability. Around the same time, ILIAD was introduced. While it began as a deterministic system, it
later adopted a Bayesian network formalism. The resulting model included 11,406 nodes, with some
structures extending to 36 levels and common findings shared by up to 62 parent nodes [14].</p>
      <p>The transition to Bayesian networks in ILIAD reflected their advantages in handling uncertainty, a
key challenge in medical reasoning [15, 16]. Bayesian networks also provide a clear graphical structure
and can model causal relationships, making them well-suited to safety-critical applications like ED
triage. In a comparative study based in the ED, ILIAD outperformed QMR, providing correct diagnoses
in 72% of cases versus QMR’s 52%, although both systems generated long diferential lists [ 17].</p>
      <p>ML has been used in emergency medicine applications such as predicting hospital admission [18, 19],
workflow optimisation [ 20, 21], critical care [22, 23], and specific conditions such as sepsis or stroke
[24, 25]. However, the lack of explainability in many of these models raises concerns [26, 8]. To address
these concerns, recent research has focused on translating rule-based expert systems into Bayesian
networks (e.g., [27, 28]).</p>
      <p>ML has been used to detect clinically relevant patient characteristics from visual and auditory data.
For example, there are several approaches to cough detection and classification using audio recordings,
with many models able to distinguish between wet and dry coughs, as well as coughs associated with
specific conditions such as Covid-19 or pertussis [ 29, 30, 31]. Similarly, jaundice has been detected
from images of the sclera and skin using models trained to either predict levels of bilirubin, an
orangeyellow pigment formed by the breakdown of red blood cells, or to classify images as jaundiced or
non-jaundiced [32, 33, 34]. Much of the existing work in this area focusses on neonatal jaundice, with
limited application to adult patients. In most cases, a colour reference square is included in the images
to support colour normalisation during preprocessing. Facial droop, such as droop on one side of the
face, has also been detected using ML models trained on facial images [35, 36, 37]. Common approaches
typically include face detection, facial landmark extraction, and the measurement of distances between
key points to identify asymmetry.</p>
      <p>While ML classifiers have been developed for a range of individual clinically relevant patient
characteristics, we are not aware of any existing work that combines them within a single expert system to
support clinical decision-making. To address this gap, we build upon DAISY, which was selected as the
foundation for this research because it is actively maintained and specifically tailored to emergency
triage. As members of the DAISY team, we have direct access to the codebase and to the clinical
collaborators involved in its development. This makes it a more suitable platform than larger but less
accessible systems such as INTERNIST-I.</p>
    </sec>
    <sec id="sec-3">
      <title>3. Approach</title>
      <sec id="sec-3-1">
        <title>3.1. Background</title>
        <p>DAISY [7, 9, 10], the CDSS on which our research is focused, gathers four categories of medically
relevant information for an ED patient being triaged:
• Demography: The patient’s medical history
• Anatomical: Specific parts of the body afected.
• Subjective: Symptoms reported directly by the patient.
• Objective: The patient’s vital signs.</p>
        <p>Demographic</p>
        <p>Anatomical</p>
        <p>Subjective</p>
        <p>Objective
Sensors</p>
        <p>Formally Veri ed</p>
        <p>ML Models
...</p>
        <p>Obs. 2</p>
        <p>Obs. 1</p>
        <p>Output
Con dence</p>
        <p>Level</p>
        <p>Bayesian
Network</p>
        <p>Rule-Based</p>
        <p>Expert
System</p>
        <p>Enhanced
Triage Report</p>
        <p>Each category includes a set of variables that collectively describe the patient’s clinical presentation
in a structured manner. For example, the Demography category includes variables such as age, sex,
and recent trauma. The Anatomical category includes variables that identify afected body parts such
as head and chest. The Subjective category includes variables representing self-reported symptoms
including pain and nausea. The Objective category includes variables for vital signs such as pulse rate
and temperature.</p>
        <p>The values of the variables within the Demography, Anatomical, and Subjective categories are
obtained by asking the patient questions, which they answer via a touch-screen interface. The Objective
category is obtained by instructing the patient to use medical devices in the room to measure their vital
signs.</p>
        <p>This information is processed by dAvInci, the rule-based expert system at the core of the DAISY
project. dAvInci currently uses over 200 doctor-specified rules to output the patient’s triage score and a
set of potential assessments, suggested investigations, treatments and referrals. A triage report, which
contains the information gathered by DAISY alongside the output from dAvInci, is made available to
the patient’s doctor.</p>
        <p>DAISY is not merely conceptual. It has been implemented in a clinical setting and is currently
undergoing a feasibility study at Scarborough Hospital as part of a registered clinical trial [11]. The
study will involve 100 patients and will evaluate DAISY’s acceptability, consultation duration, patient
engagement, and clinical concordance compared to standard triage. These measures will provide insight
into how well DAISY fits into real-world practice and how its outputs align with clinician assessments.
The study will also generate real-world triage data to support the evaluation of the Bayesian network
approach developed in this research.</p>
      </sec>
      <sec id="sec-3-2">
        <title>3.2. Overview</title>
        <p>1. Component 1 (Verified ML models). Addressing RQ2, this component enables DAISY to
capture clinically-relevant patient characteristics, allowing future variants of the system to mimic
aspects of clinical intuition.
2. Component 2 (Bayesian network). Addressing RQ1, this component augments DAISY with
probabilistic reasoning, allowing the system to represent uncertainty and generate outputs such
as probability-ranked assessments, with a view to better support clinical decision-making.
The integration of these two components (RQ3) extends the existing DAISY framework by combining
probabilistic reasoning with clinically relevant patient characteristics.</p>
      </sec>
      <sec id="sec-3-3">
        <title>3.3. Component 1: Verified ML for Patient Characteristics</title>
        <p>Doctors routinely use all their senses when assessing patients, drawing on years of experience to make
quick, intuitive judgements. This ‘clinical intuition’ often involves the subconscious recognition of
subtle but clinically significant characteristics and plays an important role in patient assessment.</p>
        <p>The enhanced DAISY aims to mimic this capability by using formally verified ML models to classify
patient characteristics captured by external sensors, such as cameras and microphones. Each classifier
outputs both a prediction and an associated confidence score, which can then be used to augment the
structured data captured by DAISY, leading to improved decision-making.</p>
      </sec>
      <sec id="sec-3-4">
        <title>3.4. Component 2: Bayesian Network for Probabilistic Reasoning</title>
        <p>To supplement DAISY’s deterministic reasoning, we introduce a Bayesian network. Bayesian networks
are particularly well-suited to healthcare applications, as they capture both causal relationships between
symptoms and diseases and the uncertainty inherent in medical reasoning. This is important because,
while patterns do exist, no two patients present in exactly the same way.</p>
        <p>An additional strength of Bayesian networks is their graphical structure, which makes the reasoning
process more interpretable. In a safety-critical domain such as emergency medicine, explainability is
essential because clinicians must be able to understand and trust the system’s outputs.</p>
        <p>By incorporating and quantifying uncertainty in this way, potential assessments can be ordered
according to their probability, thereby significantly enhancing the triage reports currently produced by
DAISY.</p>
        <sec id="sec-3-4-1">
          <title>3.4.1. Single Malady Example</title>
          <p>To illustrate this approach, we use ‘SIRS; Meningitis’ as a running example.1 It is one of over 200
maladies in DAISY’s knowledge base.</p>
          <p>Example: SIRS; Meningitis
Consider a rule for identifying possible SIRS; Meningitis. The rule is triggered if the following conditions
are met:
• Demography The patient has no history of recent physical trauma
• Anatomy and Subjective The patient reports a problem with their head and is bothered by bright
lights (photophobia)
• Objective At least two of the following are true: abnormal temperature (e.g., low or high), elevated
respiratory rate, elevated pulse rate
This rule can be formalised as:</p>
          <p>Demography_RecentTrauma = no
∧ Head_BotheredByBrightLights = yes
∧ ((Objective_Temperature ≠ normal ∧ Objective_RespiratoryRate = high)
∨ (Objective_Temperature ≠ normal ∧ Objective_PulseRate = high)
∨ (Objective_RespiratoryRate = high ∧ Objective_PulseRate = high))
⟹ Malady_SIRSMeningitis = yes
1We use the label ‘SIRS; Meningitis’ to refer to cases where systemic inflammatory response syndrome (SIRS) is present in
conjunction with or as a result of meningitis.</p>
          <p>Our aim is to encode this logic within a Bayesian network, using probabilities to relax the original
strict binary rules. Rather than requiring at least two abnormal vital signs to consider SIRS; Meningitis
as a potential assessment, the probability should increase with each abnormal vital sign. This provides
a more flexible and realistic way to support clinical decision-making under uncertainty.</p>
        </sec>
      </sec>
      <sec id="sec-3-5">
        <title>3.5. Integration</title>
        <p>The integration of verified ML classifiers with the Bayesian network enables the enhanced DAISY
system to incorporate clinically relevant patient characteristics into its probabilistic reasoning. Each
classifier detects a specific characteristic using sensor data and outputs both a prediction and confidence
score.</p>
        <p>For each characteristic, two nodes are added to the Bayesian network: one representing the classifier’s
prediction, and the other its degree of confidence in that output. These nodes are connected directly to
the relevant malady nodes, with the direction of the link going from the malady to the classifier nodes.</p>
        <p>The classifier outputs and their confidences are then used as evidence during inference, allowing
them to influence the probabilities of associated maladies. For example, if a jaundice classifier returns
a positive result with high confidence, the probability of related conditions such as liver disease or
pancreatitis increases. If the confidence is low, the efect on the probability is lesser.</p>
        <p>As part of the integration process, synthetic data must be generated to train the updated Bayesian
network and evaluate its performance. This is non-trivial and will require close collaboration with
medical experts to ensure the data is realistic.</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. Methodology</title>
      <p>The methodology for the delivery of the approach summarised in the previous section is presented
below on a per component basis.</p>
      <sec id="sec-4-1">
        <title>4.1. Verified ML for Patient Characteristics</title>
        <p>A review of relevant ML and clinical research literature was conducted, and an interview with an
emergency medicine consultant helped identify a set of clinically relevant characteristics. As detailed
in Section 5.1, one characteristic was selected from this set of shortlisted characteristics based on its
clinical usefulness, detection feasibility, and suitability for data collection.</p>
        <p>For the characteristic used in this study, no suitable open-access dataset was available, so a clinical
study was initiated to collect the required data. If additional characteristics were to be incorporated,
appropriate datasets would need to be identified or new data collected as necessary. Data augmentation
techniques were applied to increase dataset size where appropriate.</p>
        <p>A suitable formally verified ML model will be created and validated for the chosen characteristic.</p>
      </sec>
      <sec id="sec-4-2">
        <title>4.2. Bayesian Network for Probabilistic Reasoning</title>
        <p>The structure of the Bayesian network is derived from DAISY’s existing expert rule base. Each
variable appearing in one of the DAISY categories Demography, Objective and Malady is mapped to a
corresponding node in the Bayesian network. Symptoms are always recorded with a corresponding
anatomical variable in DAISY, and these are combined into a single node type Anatomy_Subjective in
the Bayesian network. DAISY also includes a special Anatomy variable ‘General’, to indicate that a
symptom is not localised to a specific anatomical location (e.g. nausea).</p>
        <p>Directed edges are added to the network based on predefined causal assumptions representing clinical
knowledge:
• Demography → Malady A patient’s demographic and medical history can influence the
probability of developing certain conditions.
• Malady → Anatomy_Subjective, Objective Once present, a malady is expected to cause
symptoms and physiological changes.</p>
        <p>Nodes from Demography, Anatomy_Subjective, and Objective may be connected to multiple Malady
nodes, reflecting the fact that a single variable (e.g. temperature) can be associated with several possible
conditions. The Bayesian network also supports directed links between Malady nodes themselves,
capturing relationships where one condition may influence the likelihood or severity of another. This
represents a key extension beyond the current DAISY system, which does not account for any
comorbidities. We are currently exploring options for which co-morbidities to include in the Bayesian
network.</p>
        <p>Continuous variables such as temperature and respiratory rate are discretised into clinically
meaningful intervals, based on thresholds defined in DAISY’s existing rule base. Although not reported here,
we are also experimenting with representing these variables as continuous nodes within the Bayesian
network to allow for more flexible modelling.</p>
        <p>The network construction was implemented using the Bayes Server [38] Java API within R. The
structure of the DAISY rule base permitted the majority of the network topology to be generated
programmatically in a systematic and eficient manner.</p>
        <sec id="sec-4-2-1">
          <title>4.2.1. Single Malady Example</title>
          <p>For our running example, SIRS; Meningitis, we constructed the structure of the Bayesian network from
the corresponding rules in DAISY’s knowledge base. As no suitable real-world dataset was available, we
generated synthetic data for 1000 patients using an R script. The distributions were designed to reflect
realistic ED conditions and to conform to DAISY’s original rule constraints. The dataset was split into
700 records for training and 300 for testing, and training was performed using Bayes Server’s Relevance
Tree algorithm, chosen for its eficiency and compatibility with discrete and discretised variables. This
single-malady example is intended to demonstrate the feasibility of network construction and parameter
learning, while the full Bayesian network will ultimately be trained on real-world ED triage data, such
as that currently being collected as part of a clinical trial for DAISY.</p>
          <p>Descriptions of the variables used in this example are provided in Table 1. Continuous variables were
discretised into clinically meaningful intervals. For example, temperature was divided into five states
(e.g., Very Low [0, 35], Low [35.1, 36], etc.), respiratory rate into five states, and pulse rate into six states.</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>5. Preliminary Results</title>
      <sec id="sec-5-1">
        <title>5.1. Verified ML for Patient Characteristics</title>
        <p>The review of the clinical research literature (e.g., [39, 40, 41, 42, 43]) led to ten broad categories of
clinically-relevant patient characteristics being identified:
• Skin (condition, hydration)
• Gait and Movement
• Respiration (rate, depth, coughing, choking, wheezing)
• Behaviour (emotional state, communication)
• Level of Consciousness
• Facial Features and Expressions
• Eyes (sclera colour, symmetry, blinking, pupil size, reaction)
• Personal Hygiene, Grooming and Dress (e.g., cleanliness)
• Position, Posture, Height and Build
• Visible Issues (bleeding, bruising, physical abnormalities)</p>
        <p>From this list, a yellow tint to the sclera (the whites of the eyes) was selected as the first characteristic
for development of an ML-detection component. This decision was informed by both the clinical
literature review and discussions with medical experts, with the intention to expand to additional
characteristics in future work.</p>
        <p>Jaundice, often characterised by yellowing of the skin and sclera, occurs due to elevated levels of
bilirubin in the blood. It can be a symptom of various underlying conditions, including liver disease,
bile duct obstruction, blood disorders, neonatal jaundice, and pancreatitis.</p>
        <p>The aim is to develop a verified ML classifier that categorises images of the sclera into one of four
classes: Yellow, Borderline, Not Yellow, Inconclusive.</p>
        <p>As no suitable open-source datasets exist, a clinical study called Measuring Icterus from Sclera Tinge
Yellowness (MiSTY) is being conducted to collect eye images and corresponding blood bilirubin levels.
This dataset will support the development and validation of a verified ML classifier for integration into
the hybrid DAISY system.</p>
      </sec>
      <sec id="sec-5-2">
        <title>5.2. Bayesian Network for Probabilistic Reasoning</title>
        <p>A full Bayesian network structure for the DAISY knowledge base has been created, consisting of 304
nodes and over 1,500 links. This network has not yet been trained.</p>
        <sec id="sec-5-2-1">
          <title>5.2.1. Single Malady Example</title>
          <p>The trained Bayesian network for the SIRS; Meningitis example was evaluated on the synthetic dataset.
The structure of the network was derived from DAISY’s rules, while the conditional probability tables
were learned from data.</p>
          <p>Figure 2 illustrates the resulting Bayesian network. As expected, the model assigns higher probabilities
of SIRS; Meningitis when more supporting evidence is present. For example, if a patient has no recent
trauma, is bothered by bright lights, and has a high temperature and high pulse rate (but a normal
respiratory rate), the model estimates a 76.9% chance that the patient has SIRS; Meningitis. If the
respiratory rate is also high, this probability increases to 93.5%.</p>
          <p>This example highlights the model’s ability to handle variation in clinical presentation, recognising
that while specific conditions are typically associated with certain patterns, patients with the same
diagnosis may difer in their medical history, afected anatomy, reported symptoms, and vital signs.</p>
          <p>Figure 3 presents box plots of the predicted probabilities for SIRS; Meningitis, grouped by the actual
class label (“Yes” or “No”). The top plot shows results on the training set, and the bottom plot shows the
test set. In both cases, the predicted probabilities are clearly separated between positive and negative
cases. Patients in the “Yes” group consistently receive higher predicted probabilities than those in the
“No” group, suggesting that the model has learned to distinguish between the two classes efectively.</p>
          <p>The similarity between training and test results suggests that the model generalises well without
signs of overfitting.</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>6. Conclusion</title>
      <p>This paper described a PhD project aiming to develop a hybrid AI solution for ED triage. The proposed
approach extends the DAISY system by introducing formally verified ML models to recognise clinically
relevant patient characteristics and a Bayesian network to support probabilistic reasoning.</p>
      <p>So far, the project has defined a preliminary system architecture, identified potential patient
characteristics to be modelled using ML, selected one characteristic, submitted a clinical study for ethical review
to provide training data, and created the structure of the Bayesian network. A single malady example
has been used to demonstrate the feasibility of applying Bayesian networks within this approach.</p>
      <p>Next steps include developing and validating the verified ML model for the selected characteristic
using data from the clinical study, training the full Bayesian network, and integrating these components.
The performance of the enhanced DAISY system will then be evaluated. Future work will also consider
advancing probabilistic reasoning under uncertainty by incorporating continuous vital signs and
modelling co-morbidities.</p>
    </sec>
    <sec id="sec-7">
      <title>Acknowledgments</title>
      <p>This research is funded by a UKRI Trustworthy Autonomous Node in Resilience Doctoral Training
Programme studentship.</p>
    </sec>
    <sec id="sec-8">
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