Prognostic value of early warning scores in the emergency department (ED) and acute medical unit (AMU): A narrative review

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Highlights

  • An abundance of early warning scores (EWS) are used in different clinical settings.

  • Different EWS have different outcomes depending on the clinical setting.

  • National Early Warning Score was the most accurate in the general population.

  • Mortality in Emergency Department Sepsis score fared best in those with infection.

  • Currently no single EWS can reliably be used throughout the whole acute care chain.

Abstract

Background

A wide array of early warning scores (EWS) have been developed and are used in different settings to detect which patients are at risk of deterioration. The aim of this review is to provide an overview of studies conducted on the value of EWS on predicting intensive care (ICU) admission and mortality in the emergency department (ED) and acute medical unit (AMU).

Methods

A literature search was conducted in the bibliographic databases PubMed and EMBASE, from inception to April 2017. Two reviewers independently screened all potentially relevant titles and abstracts for eligibility.

Results

42 studies were included. 36 studies reported on mortality as an endpoint, 13 reported ICU admission and 9 reported the composite outcome of mortality and ICU admission. For mortality prediction National Early Warning Score (NEWS) was the most accurate score in the general ED population and in those with respiratory distress, Mortality in Emergency Department Sepsis score (MEDS) had the best accuracy in patients with an infection or sepsis. ICU admission was best predicted with NEWS, however in patients with an infection or sepsis Modified Early Warning Score (MEWS) yielded better results for this outcome.

Conclusion

MEWS and NEWS generally had favourable results in the ED and AMU for all endpoints. Many studies have been performed on ED and AMU populations using heterogeneous prognostic scores. However, future studies should concentrate on a simple and easy to use prognostic score such as NEWS with the aim of introducing this throughout the (pre-hospital and hospital) acute care chain.

Introduction

Studies have consistently shown that clinical deterioration of hospitalized patients is often preceded by changes in vital signs up to 6 to 24 h before an adverse event [1], [2], [3], [4]. However, these changes in vital signs were often underreported or were disregarded [5]. In an effort to prevent these adverse events, several systems have been developed to identify patients that are most likely to deteriorate. By 2015 over 36 Early Warning Systems (EWS) were developed with variable success and rate of implementation [6]. Hospitals worldwide use different EWS and due to the large number of EWS models it might be difficult to determine which EWS is most suitable for different settings in the acute care chain. Most of the studies have investigated the value of EWS in clinical wards. However, large scale studies investigating the value of EWS on top of triage systems in the emergency department (ED) to timely detect deterioration is lacking.

Some groups have developed separate scoring systems specifically designed for medical patients in the ED. An example is the Rapid Emergency Medicine Score (REMS) that was introduced in 2004 [7]. In addition, some scores have been developed to be used specifically in certain patient groups. For example the Mortality in Emergency Department Sepsis score (MEDS) for patients with an infectious disease [8], and CURB-65 (acronym for Confusion, Urea nitrogen, Respiratory rate, Blood pressure and age  65) for patients with pneumonia [9].

Different types of EWS have also been used in the Acute Medical Unit (AMU), which is a department that has been implemented in several countries to optimize care for acutely admitted medical patients [10]. This department is essentially a multi-disciplinary gateway between the emergency department and the ward of the hospital caring for acutely admitted during the first 72 h. However patients can only be admitted from the outpatients setting to the AMU, but not from a ward to the AMU [11], [12].

As specialists in (acute) internal medicine, we see our patients both in ED, the AMU and the clinical wards. A uniform scoring system in the acute care chain would be preferable instead of using separate scores for ED, the AMU and the clinical wards. For the purpose of this review, we decided to provide an overview of the prognostic value of various (early warning) scores in predicting mortality or ICU admission that have been studied in medical patients in the ED and in the AMU.

Section snippets

Study identification/search strategy

To identify all relevant publications, we performed a systematic search on 15 April 2017 in the bibliographic databases PubMed and EMBASE from inception to April 2017. Search terms included controlled terms from MeSH in PubMed, EMtree in EMBASE as well as free text terms. Search terms expressing “EWS” were used in combination with search terms comprising “emergency department” and terms for “Acute Medical Unit” and “adults”. The search strategy can be found in appendix 1. Subsequently, the

Study characteristics

Of the total 1651 citations that were found, 71 articles were assessed for eligibility of which 42 studies were found suitable for inclusion (Fig. 1. Flowchart). The study characteristics of these 42 studies can be found in Table 1 (study characteristics). A total of 25 different types of EWS were identified in these 42 articles. The most frequently used prognostic scores were the Modified Early Warning Score (MEWS), which was applied in 19 studies [15], [16], [17], [18], [19], [20], [21], [22]

Discussion

We conclude that a wide array of prognostic scores is in use in different settings with a considerable heterogeneity in the used parameters. All studies that included AUROC for one or more outcome measures found AUROCs which were far greater than > 0.5, which is the cut-off for correlation that is reached by chance alone [14]. The majority of the studies that objectified the performance of EWS with either HR, OR, RR or p value found a strong significant correlation with their outcome variables.

Conclusion

Evidence regarding the prognostic value of EWS in the ED and AMU is hampered by the use of a large array of similar, yet slightly different scoring systems. A reliable comparison among these systems is therefore difficult. The ideal EWS is both simple and accurate, with few chances of calculation errors and can be used in the whole acute care chain. No prognostic score can impeccably detect all patients at risk of an adverse outcome. Therefore EWS should not replace clinical judgement, but

Conflicts of interest

None

Acknowledgements

Information analyst, Ralph de Vries.

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