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Validation of the National Emergency Department Overcrowding Score (NEDOCS) in a UK non-specialist emergency department
  1. Duncan Hargreaves1,
  2. Sophie Snel2,
  3. Colin Dewar3,
  4. Khushal Arjan2,
  5. Piervirgilio Parrella4,
  6. Luke Eliot Hodgson5,6
  1. 1 Intensive Care Medicine and Anaesthesia, Western Sussex Hospitals NHS Foundation Trust, Worthing, UK
  2. 2 Medical Student, Brighton and Sussex Medical School, Brighton, Brighton and Hove, UK
  3. 3 Emergency Department, Western Sussex Hospitals NHS Foundation Trust, Worthing, UK
  4. 4 Research Department, Western Sussex Hospitals NHS Foundation Trust, Worthing, West Sussex, UK
  5. 5 Intensive Care, Western Sussex Hospitals NHS Foundation Trust, Worthing, W Sussex, UK
  6. 6 University of Surrey Faculty of Health and Medical Sciences, Guildford, Surrey, UK
  1. Correspondence to Dr Duncan Hargreaves, Intensive Care Medicine and Anaesthesia, Western Sussex Hospitals NHS Foundation Trust, Worthing BN11 2DH, UK; duncan.hargreaves{at}


Introduction Emergency department (ED) crowding has significant adverse consequences, however, there is no widely accepted tool to measure it. This study validated the National Emergency Department Overcrowding score (NEDOCS) (range 0–200 points), which uses routinely collected ED data.

Methods This prospective single-centre study sampled data during four periods of 2018. The outcome against which NEDOCS performance was assessed was a composite of clinician opinion of crowding (physician and nurse in charge). Area under the receiver operating characteristic curves (AUROCs) and calibration plots were produced. Six-hour stratified sampling was added to adjust for temporal correlation of clinician opinion. Staff inter-rater agreement and NEDOCS association with opinion of risk, safety and staffing levels were collected.

Results From 905 sampled hours, 448 paired observations were obtained, with the ED deemed crowded 18.5% of the time. Inter-rater agreement between staff was moderate (weighted kappa 0.57 (95% CI 0.56 to 0.60)). AUROC for NEDOCS was 0.81 (95% CI 0.77 to 0.86). Adjusted for temporal correlation, AUROC was 0.80 (95% CI 0.73 to 0.88). At a cut-off of 100 points sensitivity was 75.9% (95% CI 65.3% to 84.6%), specificity 72.1% (95% CI 67.1% to 76.6%), positive predictive value 38.2% (95% CI 30.7% to 46.1%) and negative predictive value 92.9% (95% CI 89.3% to 95.6%). NEDOCS underpredicted clinical opinion on Calibration assessment, only partially correcting with intercept updating. For perceived risk of harm, safety and insufficient staffing, NEDOCS AUROCs were 0.71 (95% CI 0.61 to 0.82), 0.71 (95% CI 0.63 to 0.80) and 0.70 (95% CI 0.64 to 0.76), respectively.

Conclusions NEDOCS demonstrated good discriminatory power for clinical perception of crowding. Prior to implementation, determining individual unit ED cut-off point(s) would be important as published thresholds may not be generalisable. Future studies could explore refinement of existing variables or addition of new variables, including acute physiological data, which may improve performance.

  • crowding
  • efficiency
  • emergency department
  • management
  • risk management

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  • Handling editor Richard Body

  • Contributors DH and CD conceived the study. DH, LEH and PP designed the analysis. CD led clinician data collection. PP advised on sample size and stratification. LEH, PP, SS and KA provided statistical support and analysis. DH and SS wrote the first draft of the manuscript. All authors have read and approved the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • Patient consent for publication Not required.

  • Ethics approval The study data comprised anonymised data recorded in the medical record as part of routine patient care and HRA approval for the study was sought (IRAS ID: 214461) but deemed not necessary.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available on reasonable request. Data available on reasonable request to the corresponding author of the article.