Strengths and limitations of early warning scores: A systematic review and narrative synthesis

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Abstract

Background

Early warning scores are widely used to identify deteriorating patients. Whilst their ability to predict clinical outcomes has been extensively reviewed, there has been no attempt to summarise the overall strengths and limitations of these scores for patients, staff and systems. This review aims to address this gap in the literature to guide improvements for the optimization of patient safety.

Methods

A systematic review was conducted of MEDLINE®, PubMed, CINAHL and The Cochrane Library in September 2016. The citations and reference lists of selected studies were reviewed for completeness. Studies were included if they evaluated vital signs monitoring in adult human subjects. Studies regarding the paediatric population were excluded, as were studies describing the development or validation of monitoring models. A narrative synthesis of qualitative, quantitative and mixed- methods studies was undertaken.

Findings

232 studies met the inclusion criteria. Twelve themes were identified from synthesis of the data: Strengths of early warning scores included their prediction value, influence on clinical outcomes, cross-specialty application, international relevance, interaction with other variables, impact on communication and opportunity for automation. Limitations included their sensitivity, the need for practitioner engagement, the need for reaction to escalation and the need for clinical judgment, and the intermittent nature of recording.

Early warning scores are known to have good predictive value for patient deterioration and have been shown to improve patient outcomes across a variety of specialties and international settings. This is partly due to their facilitation of communication between healthcare workers.

There is evidence that the prediction value of generic early warning scores suffers in comparison to specialty-specific scores, and that their sensitivity can be improved by the addition of other variables. They are also prone to inaccurate recording and user error, which can be partly overcome by automation.

Conclusions

Early warning scores provide the right language and environment for the timely escalation of patient care. They are limited by their intermittent and user-dependent nature, which can be partially overcome by automation and new continuous monitoring technologies, although clinical judgment remains paramount.

Introduction

The early warning score system is predicated on the idea that derangements in simple physiological observations can identify hospital inpatients at high risk of deterioration (Goldhill and McNarry, 2004). Prodromal warning signs such as increased respiratory rate or decreased blood pressure precede critical illness (Ridley, 2005), and early recognition of these events presents an opportunity for decreasing mortality (Bleyer et al., 2011). The early warning score system allows the user to record and respond to multiple parameters simultaneously, so that subtle changes in vital signs can be used to initiate early emergency management of the patient to reverse the abnormal physiological decline or prompt admission to a critical care area (Ridley, 2005).

Early warning scores have been widely adopted internationally, and different versions exist. A number of reviews have examined the impact of early warning scores on patient outcomes; however, there exists no formal literature review regarding the overall strengths and limitations of early warning scores for patients, staff and systems. This review aims to address this knowledge gap and provide an overview of current systems, highlighting the benefits and identifying areas for future improvement.

Section snippets

Study design

A systematic review methodology was adopted for the study, employing the principles and methods provided by the Centre for Reviews and Dissemination guidelines and following the PRISMA statement. A narrative synthesis approach was chosen to synthesise the diverse range of selected studies in a structured manner, following the European Social Research Council Guidance on the Conduct of Narrative Synthesis in Systematic Reviews (Popay et al., 2006).

Search strategy

A systematic review of the scientific literature

Findings

The search identified 825 papers (285 Medline, 359 PubMed, 176 CINAHL and 5 Cochrane). Duplicates were eliminated. 232 papers met the inclusion criteria. A flow diagram of the search process is shown in Fig. 1.

There was 100% inter-rater agreement between CD and WT.

Prediction value

Early warning scores have consistently been found to accurately predict adverse outcomes in a number of different populations. Despite being developed for general medical hospital admissions, a recent retrospective study of 35 174 surgical admissions found that NEWS discriminated deterioration in non-elective surgical patients at least as well as in non-elective medical patients (Kovacs et al., 2016).

Early warning scores have been found to be excellent predictors of cardiac arrest (Churpek et

Sensitivity, especially compared to specialty-specific scores

In 2003, Boyle reported that early warning scoring systems were largely unproven and could prove to be over-sensitive and unspecific (Boyle, 2003). However, the evidence base has grown and a recent study from Hong Kong found that MEWS has a 100% sensitivity and a 98.3% specificity in detecting patient deterioration (Shuk-Ngor et al., 2015).

Nevertheless, early warning scores are generic tools which should be used to complement, but not necessarily replace, existing prediction tools (Barlow et

Discussion

This systematic review and narrative synthesis was conducted to explore the literature regarding the strengths and limitations of early warning score vital signs monitoring systems, for both patients and clinical teams. To our knowledge, this is the first literature review to systematically assess the extent of the evidence around these tools.

Early warning scores have become ubiquitous with the recognition of the deteriorating patient. This review confirms that early warning scores have

Conclusion

This review has shown that early warning scores are successful in predicting and improving patient outcomes across a range of settings and populations. The most important advantage of early warning scores is that they are easy to use and interpret, and so provide a common language across healthcare providers and specialties. However, inaccurate recordings or inappropriate reactions to abnormal scores can undermine the benefits of these systems.

Harnessing their strengths and recognizing their

Originality

This article is an original work, has not been published before, and is not being considered for publication elsewhere in its final form, in either printed or electronic media. It is not based on any previous communication to a society or meeting.

Funding sources

This review is independent research arising from a Doctoral Research Fellowship (Candice Downey, DRF-2016-09-03) supported by the National Institute for Health Research. The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research, Health Education England or the Department of Health.

DGJ received funding support through an NIHR Research Professorship.

The authors acknowledge assistance from the NIHR Healthcare

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