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

Abstract

ObjectivesIdentifying 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.DesignCase–control study.SettingSecondary and tertiary hospitals in the Netherlands.ParticipantsThe 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 measuresThe primary outcome was one or more positive SARS-CoV-2 PCR test results within 1 day prior to or 1 week after ED presentation.ResultsThe 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.ConclusionsThe 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.

Validating a clinical laboratory parameter-based deisolation algorithm for patients with COVID-19 in the intensive care unit using viability PCR: the CoLaIC multicentre cohort study protocol

“…The CoLab score 10 uses the erythrocytes (×10 12 /L), leucocytes (×10 9 /L), eosinophils (×10 9 /L), basophils (×10 9 /L), log 10 of bilirubin (µmol/L), log 10 of lactate dehydrogenase (U/L), log 10 of alkaline phosphatase (IU/L), log 10 of γ-glutamyltransferase (U/L), albumin (g/L), C-reactive protein (mg/L) and age (years accurate to two decimals). These parameters are routinely measured in ICU patients and can be automatically extracted from the laboratory information system.…”

“…These parameters are routinely measured in ICU patients and can be automatically extracted from the laboratory information system. The CoLab algorithm yields a score in the range of −20 to 5 (the so-called CoLab linear predictor 10 ), with a lower score associated with the exclusion of a SARS-CoV-2 infection and a higher score reflecting an increased risk of SARS-CoV-2 infection.…”

“…This cut-off was originally set to −5.83 to minimise the amount of false negative results, with a score below −5.83 being negative for COVID-19. 10 How the CoLab algorithm corresponds with a negligible intact infectious viral load (see the section below) is part of the present study: a cut-off or a certain decrease in CoLab score over time. The CoLab score will be calculated daily for all participating patients, either prospectively or retrospectively.…”

“…This score has been developed using an adaptive least absolute shrinkage and selection operator (LASSO) regression technique and requires the input of the numerical results of 10 blood parameters and the age of the patient. 10 The required parameters are blood tests that are requested frequently and routinely for emergency room (ER) as well as ICU patients. This score has previously been developed and validated and has been implemented in the ER departments of two large Dutch teaching hospitals, with very high negative predictive value (99.5%) and sensitivity (96.9%).…”

“…One of the methods to assess the host response to SARS-CoV-2 is the CoLab score. This score has been developed using an adaptive least absolute shrinkage and selection operator (LASSO) regression technique and requires the input of the numerical results of 10 blood parameters and the age of the patient 10. The required parameters are blood tests that are requested frequently and routinely for emergency room (ER) as well as ICU patients.…”