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Risk stratification of patients admitted to hospital with covid-19 using the ISARIC WHO Clinical Characterisation Protocol: development and validation of the 4C Mortality Score

BMJ 2020; 370 doi: https://doi.org/10.1136/bmj.m3339 (Published 09 September 2020) Cite this as: BMJ 2020;370:m3339

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Re: Risk stratification of patients admitted to hospital with covid-19 using the ISARIC WHO Clinical Characterisation Protocol: development and validation of the 4C Mortality Score

Dear Editor

Knight and colleagues have developed and validated a pragmatic risk score that predicts mortality in patients with COVID-19. The study is arguably the largest of its kind; the statistical analysis is extensive and relatively robust; and the score is simple enough to be applied in clinical practice.

Clinicians must understand that this score won’t differentiate COVID-19 from other similar clinical presentations at the front door, where this score is intended to be used. Many times, the patient who presents with severe breathlessness to emergency departments or their GPs will have not yet had a confirmatory SARS-CoV-2 nasopharyngeal PCR result. Differentials for a breathless patient, even with bilateral shadowing on a concomitant chest x-ray are broad. This includes acute heart failure, atypical bacterial pneumonia and with the winter looming, acute influenza.

To complicate matters further, any patient with severe disease from the aforementioned conditions would score highly on the 4C Mortality Score; but their management, and therefore prognosis would be different to what the score predicts, depending on their condition and appropriate subsequent use of diuretics or antimicrobial therapy. For example, an elderly patient in acute heart failure (giving them drop in mental status, raised urea, oxygen requirements and raised respiratory rate) may be inadvertently given steroids due to a misdiagnosis of COVID-19 and a high scoring 4C Mortality Score, when all they actually required was adequate diuresis.

The second wave of COVID-19 is on the horizon in the UK. Thanks to huge efforts in research, we are now better equipped to deal with the disease. However, the clinical history and examination remain critical in ensuring the diagnosis of COVID-19 is correct; so that correct interventions are targeted at those who need them, and that patients presenting to healthcare with similar diseases other than COVID-19 do not come to harm.

Competing interests: No competing interests

16 September 2020
Daniel Pan
NIHR Academic Clinical Fellow in Infectious Diseases
Department of Respiratory Sciences
University of Leicester