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