BMJ Open (Aug 2022)

Development and validation of an early warning score to identify COVID-19 in the emergency department based on routine laboratory tests: a multicentre case–control study

  • Volkher Scharnhorst,
  • Madelon M Buijs,
  • Heidi S M Ammerlaan,
  • Arjen-Kars Boer,
  • Ruben Deneer,
  • Maaike Maas,
  • Roland H H van Balkom,
  • Wendy A H M Thijssen,
  • Sophie Bennenbroek,
  • Mathie Leers,
  • Remy J H Martens,
  • Jos J Kerremans,
  • Muriël Messchaert,
  • Jeroen J van Suijlen,
  • Natal A W van Riel

DOI
https://doi.org/10.1136/bmjopen-2021-059111
Journal volume & issue
Vol. 12, no. 8

Abstract

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Objectives Identifying patients with a possible SARS-CoV-2 infection in the emergency department (ED) is challenging. Symptoms differ, incidence rates vary and test capacity may be limited. As PCR-testing all ED patients is neither feasible nor effective in most centres, a rapid, objective, low-cost early warning score to triage ED patients for a possible infection is developed.Design Case–control study.Setting Secondary and tertiary hospitals in the Netherlands.Participants The study included patients presenting to the ED with venous blood sampling from July 2019 to July 2020 (n=10 417, 279 SARS-CoV-2-positive). The temporal validation cohort covered the period from July 2020 to October 2021 (n=14 080, 1093 SARS-CoV-2-positive). The external validation cohort consisted of patients presenting to the ED of three hospitals in the Netherlands (n=12 061, 652 SARS-CoV-2-positive).Primary outcome measures The primary outcome was one or more positive SARS-CoV-2 PCR test results within 1 day prior to or 1 week after ED presentation.Results The resulting ‘CoLab-score’ consists of 10 routine laboratory measurements and age. The score showed good discriminative ability (AUC: 0.930, 95% CI 0.909 to 0.945). The lowest CoLab-score had high sensitivity for COVID-19 (0.984, 95% CI 0.970 to 0.991; specificity: 0.411, 95% CI 0.285 to 0.520). Conversely, the highest score had high specificity (0.978, 95% CI 0.973 to 0.983; sensitivity: 0.608, 95% CI 0.522 to 0.685). The results were confirmed in temporal and external validation.Conclusions The CoLab-score is based on routine laboratory measurements and is available within 1 hour after presentation. Depending on the prevalence, COVID-19 may be safely ruled out in over one-third of ED presentations. Highly suspect cases can be identified regardless of presenting symptoms. The CoLab-score is continuous, in contrast to the binary outcome of lateral flow testing, and can guide PCR testing and triage ED patients.