Badriyah, Tessy

Briggs, Jim

Featherstone, Peter

Jarvis, Stuart

Kovacs, Caroline

Meredith, Paul

Mohammed, Mohammed A.

Prytherch, David

Schmidt, Paul

Smith, Gary

English

Portsmouth University Research Portal (Pure)

Introduction
In the UK, most hospitals use an EWS to identify patients at highest risk and provide appropriate 
care. These are based on measurements of vital signs (e.g., pulse rate, blood pressure, breathing 
rate and conscious level). Use of the National Early Warning Score (NEWS, Table 1) is 
recommended3.
Although measured less often than vital signs, laboratory tests are subject to strict quality control 
and have independently been identified as risk factors for poor patient outcome4. LDT-EWS (Table 
2), an EWS based exclusively on laboratory test results, has been shown to discriminate patients at 
risk of hospital mortality1,2.
We hypothesised that combining LDT-EWS with NEWS would improve the discrimination of 
hospital mortality compared with each system individually. As both EWS are calculated by 
summing scores for measured values, it would be simple to combine them by summing the NEWS 
and LDT-EWS scores for a given patient.
B
B
C
Aim
To determine whether combining an early warning score (EWS) based exclusively on laboratory 
tests (LDT-EWS1,2) with the National Early Warning Score (NEWS3) would improve the 
discrimination of hospital mortality compared with each system individually. 
Methods
We used a combined 
electronic database of 
haematology, 
biochemistry and vital 
signs measurements 
collected routinely 
soon after admission 
for 88695 adult 
admissions for whom 
the admission 
speciality was 
Medicine.
The data were divided 
into 23 sets (Q1-Q23), 
each corresponding to 
three months. LDT-
EWS was generated
using decision tree analysis of haematology and biochemistry results for episodes from set Q1 
(n=3762)1,2.
LDT-EWS was applied to haematology and biochemistry results and NEWS was applied to vital 
signs measurements in 22 discrete test data sets each of three months long (Q2, Q3......Q23) 
(range of n = 3580 to 4186).
A combined EWS was determined for each episode by summing, for each episode, the values for 
NEWS and LDT-EWS.
The abilities of NEWS, LDT-EWS and the combined EWS to discriminate in-hospital death were 
assessed using the area under the receiver-operating characteristic (AUROC) curve and by plotting 
EWS efficiency curves. The efficiency curves provide a relative measure, for a given trigger value in 
an EWS, of the number of triggers and number of patients subsequently dying that would be 
visited.
Table 1: NEWS, the National Early Warning Score.
3 2 1 0 1 2 3
Resp. Rate (/min) ≤8 9–11  12–20 21–24 ≥25
SpO2 (%) ≤91 92–93 94–95 ≥96
Supplemental O2 Yes No
Temperature (°C) ≤35.0    35.1-36.0 36.1–38.0 38.1–39.0   ≥39.1
Systolic BP (mmHg) ≤90 91–100 101–110 111–219 ≥220
Heart rate (/min) ≤40 41–50 51–90 91–110 111–130 ≥131
Conscious level    Alert Not alert
Conclusions
This study provides evidence that a combined EWS using commonly measured laboratory tests 
and vital signs better discriminates in-hospital mortality than using either an EWS based on 
laboratory data or vital signs alone. We hypothesise that, with appropriate modification, the 
combined EWS could be used for identification of patients at high risk of death in the short term 
(for example, 24 hour mortality). 
References
1. Jarvis S, Kovacs C, Badriyah T, Briggs J, Mohammed M, Meredith P, Schmidt P, Featherstone P, Prytherch D, Smith GB. Decision Tree Early Warning Scores based on common laboratory test results 
discriminate patients at risk of hospital mortality, 8th International Rapid Response Conference, 13-14 May, 2013, Royal College of Physicians, London
2. Jarvis S, Kovacs C, Badriyah T, Briggs J, Mohammed M, Meredith P, Schmidt P, Featherstone P, Prytherch D, Smith GB. Development and validation of a decision tree early warning score based on 
routine laboratory test results for the discrimination of hospital mortality. Submitted to Resuscitation
3. National Early Warning Score (NEWS): Standardising the assessment of acute-illness severity in the NHS. Report of a working party. 2012, Royal College of Physicians, London
4. Prytherch D, Sirl J, Schmidt P, Featherstone P, Weaver PC, Smith GB. The use of routine laboratory data to predict in-hospital death in medical admission. Resuscitation 2005;66:203-207
Combining the National Early Warning Score with an early warning score based on 
common laboratory test results better discriminates patients at risk of hospital 
mortality
Stuart Jarvisa, Caroline Kovacsa, Tessy Badriyaha, Jim Briggsa, Mohammed A Mohammeda,b,  Paul Meredithc, Paul Schmidtc,
Peter Featherstonec, David Prythercha,c, Gary Smithd
a Centre for Healthcare Modelling and Informatics, University of Portsmouth, Portsmouth, UK | b Primary Care Clinical Sciences, University of Birmingham, Birmingham, UK
c Portsmouth Hospitals NHS Trust, Portsmouth, UK  | d School of Health & Social Care, University of Bournemouth, Bournemouth, UK
Fig. 2: Efficiency curves for LDT-EWS, NEWS and the combined EWS against hospital mortality. 
Fig. 1: Areas under the receiver operating characteristic curve for LDT-EWS, NEWS and the 
combined EWS, against hospital mortality.
Results
The combined EWS offered the best discrimination of hospital mortality in each of the 22 test data 
sets (Fig. 1). The range of AUROC values (95% CI) were:
• LDT-EWS: 0.743 (0.718 to 0.768) (Q10) to 0.799 (0.773 to 0.825) (Q9)
• NEWS: 0.704 (0.675 to 0.733) (Q7) to 0.759 (0.732 to 0.786) (Q8)
• Combined EWS: 0.799 (0.776 to 0.822) (Q10) to 0.836 (0.813 to 0.861) (Q21)
The combined EWS also offered better performance than LDT-EWS or NEWS as measured by an 
EWS efficiency curve (Fig. 2). 
Table 2: LDT-EWS for males (top) and females (bottom).
FEMALE 3 2 1 0 1 2 3
Hb ≤12.0 12.1-14.8 ≥14.9
WCC ≤12.6 12.7-14.8 ≥14.9
U ≤8.4 8.5-13.8 ≥13.9
Cr ≤91 92-157 ≥158
Na ≤134 135-140 ≥141
K ≤3.3 3.4-4.5 ≥4.6
Alb ≤28 29-34 ≥35
MALE 3 2 1 0 1 2 3
Hb ≤11.1 11.2-12.8 ≥12.9
WCC ≤9.3 9.4-16.6 ≥16.7
U ≤9.4 9.5-13.7 ≥13.8
Cr ≤114 115-179 ≥180
Na ≤132 133-140 ≥141
K ≤3.7 3.8-4.4 4.5-4.7 ≥4.8
Alb ≤30 31-34 ≥35


Decision Tree Early Warning Scores based on common laboratory test results discriminate patients at risk of hospital mortality,

Combining the National Early Warning Score with an early warning score based on common laboratory test results better discriminates patients at risk of hospital mortality

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Combining the National Early Warning Score with an early warning score based on common laboratory test results better discriminates patients at risk of hospital mortality

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