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Comparative Study
. 2019 Oct;74(10):941-946.
doi: 10.1136/thoraxjnl-2019-213470. Epub 2019 Aug 6.

Comparison of early warning scores in patients with COPD exacerbation: DECAF and NEWS score

Carlos Echevarria  1   2 , John Steer  1   3 , Stephen C Bourke  4   3
Affiliations
Comparative Study

Comparison of early warning scores in patients with COPD exacerbation: DECAF and NEWS score

Carlos Echevarria et al. Thorax. 2019 Oct.

Abstract

Background: The National Early Warning Score 2 (NEWS2) includes two oxygen saturation scales; the second adjusts target saturations to 88%-92% for those with hypercapnic respiratory failure. Using this second scale in all patients with COPD exacerbation ('NEWS2All COPD') would simplify practice, but the impact on alert frequency and prognostic performance is unknown. Admission NEWS2 score has not been compared with DECAF (dyspnoea, eosinopenia, consolidation, acidaemia, atrial fibrillation) for inpatient mortality prediction.

Methods: NEWS, NEWS2 and NEWS2All COPD and DECAF were calculated at admission in 2645 patients with COPD exacerbation attending consecutively to one of six UK hospitals, all of whom met spirometry criteria for COPD. Alert frequency and appropriateness were assessed for all NEWS iterations. Prognostic performance was compared using the area under the receiver operating characteristic (AUROC) curve. Missing data were imputed using multiple imputation.

Findings: Compared with NEWS, NEWS2 reclassified 3.1% patients as not requiring review by a senior clinician (score≥5). NEWS2All COPD reduced alerts by 12.6%, or 16.1% if scoring for injudicious use of oxygen was exempted. Mortality was low in reclassified patients, with no patients dying the same day as being identified as low risk. NEWS2All COPD was a better prognostic score than NEWS (AUROC 0.72 vs 0.65, p<0.001), with similar performance to NEWS2 (AUROC 0.72 vs 0.70, p=0.090). DECAF was superior to all scores (validation cohort AUROC 0.82) and offered a more clinically useful range of risk stratification (DECAF=1.2%-25.5%; NEWS2=3.5%-15.4%).

Conclusion: NEWS2All COPD safely reduces the alert frequency compared with NEWS2. DECAF offers superior prognostic performance to guide clinical decision-making on admission, but does not replace repeated measures of NEWS2 during hospitalisation to detect the deteriorating patient.

Keywords: copd epidemiology; copd exacerbations.

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Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: JS has no conflicts of interest to declare. CE reports grants from National Institute of Health Research, outside of the submitted work. SCB reports grants from National Institute of Health Research, Philips Respironics and from Pfizer Open Air, personal fees from Pfizer, AstraZeneca and ResMed, and non-financial support from Boehringer Ingelheim and GlaxoSmithKline outside the submitted work. No author has financial relationships with any organisation that might have an interest in the submitted work.

Figures

Figure 1
Figure 1
Frequency of alerts for NEWS2All COPD, NEWS2 and NEWS. Figure shows the percentage of patients in each risk category, grouped together by early warning score. The first column in each group is NEWS2All COPD, the second is NEWS2 and the third is NEWS. P values were calculated using Fisher’s exact test. NEWS 5–6=medium risk, prompting urgent response by clinician/clinical team and minimum hourly observations. NEWS 7=high risk. Urgent response by clinician/clinical team, which may include critical care, and continuous monitoring or vital signs.
Figure 2
Figure 2
Histogram of NEWS scores. Figure shows all patients from the derivation and validation cohorts. The number of individuals is shown in the x-axis (‘count’) and the total NEWS2 score is shown on the y-axis. The grey lines separate low-risk (0–4), moderate-risk (5–6) and high-risk (7 or more) groups.
Figure 3
Figure 3
Receiver operator curves for the DECAF score, NEWS2All COPD and NEWS all cohorts. Figure shows the performance of the DECAF, NEWS2All COPD, NEWS2 and NEWS scores. A higher area under the receiver operating characteristic curve (‘A’) shows better prediction. DECAF is not included in the derivation cohort, as this would unfairly favour its performance.
Figure 4
Figure 4
Calibration curves for DECAF, NEWS2All COPD, NEWS2 and NEWS in all cohorts. Figure shows calibration curves for NEWS2All COPD, NEWS2 and NEWS in all patients. DECAF is shown in the validation cohort, as inclusion of the derivation cohort would unfairly favour its performance. Predicted risk is shown on the y-axis which was calculated using logistic regression analysis to give individual’s mortality risk as a percentage. The x-axis shows the observed risk, which is a proportion of the number of patients who died within an assigned risk range. The slope of the equation should be near 1 (eg, for DECAF, the slope is 1.038), and the intercept should be near 0 (for DECAF, this is 0.0022). The R2 represents the correlation between the predicted risk and observed risk using Pearson’s correlation, with scores closest to 1 showing maximum correlation.
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Comment in

  • COPD exacerbations: 2 much NEWS?
    Suh ES, Sage B. Suh ES, et al. Thorax. 2019 Oct;74(10):929-930. doi: 10.1136/thoraxjnl-2019-213788. Epub 2019 Sep 10. Thorax. 2019. PMID: 31506390 No abstract available.

References

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