Validation of the COVILUS score to diagnose COVID-19 in an emergency room cohort.

In 2020, our team published a study on the association of lung ultrasound images with COVID‐19 infection in an emergency room cohort [1]. We used the points described by the bedside lung ultrasound in emergency (BLUE) protocol (upper and lower BLUE points and posterolateral alveolar and/or pleural syndrome point) to develop a model for diagnosis of COVID‐19 in patients presenting to the Emergency Department with suspected infection [2]. We found that a combination of clinical features and lung ultrasound signs were independently associated with positive SARS‐CoV‐2 infection. Subsequent development of adult respiratory distress syndrome (ARDS) was also associated with lung ultrasound signs (≥ 3 upper lung B‐lines and ≥ 3 lower lung B‐lines).

From our previously published data, we propose a score (COVILUS score between 1 and 6 points) taking into account the coefficient of each variable of lung ultrasound in a multivariable logistic model (Table 1). We then conducted a prospective observational study to validate this score on an independent cohort. Participants gave informed consent. We studied 100 patients admitted to the emergency room who underwent lung ultrasound for suspected COVID‐19 infection as part of the BLUE protocol and who had a SARS‐CoV‐2 test. An independent, blinded clinician calculated the scores. Mean (SD) age was 67 (17) years and mean (SD) BMI was 28 (6) kg.m‐2. Twenty‐nine patients had a positive SARS‐CoV‐2 test and 12 of these (41%) developed ARDS, six (21%) were admitted to ICU, four (14%) suffered a pulmonary embolism, three (10%) developed a secondary bacterial infection and six (21%) died. The area (95%CI) under the receiver operating characteristic curve of the COVILUS score was 0.92 (0.85–0.99). A score ≥ 4 could predict a positive SARS‐CoV‐2 test; sensitivity, 94% (86–98%); specificity, 66% (46–82%); positive predictive value, 53% (40–91%); and negative predictive value, 96% (86–97%). The odds ratio (95%CI) for subsequent ARDS in patients with COVID‐19 was also independently associated with: ≥ 3 upper site B‐lines, 1.55 (1.08–2.24), p = 0.03 and ≥ 3 lower site B‐lines, 1.69 (1.23–2.31), p = 0.003.

Table 1

COVILUS score

Lung ultrasound signs	Points
Upper BLUE point: B lines ≥ 3	1
Lower BLUE point: Thickened pleura	1
Lower BLUE point: Subpleural consolidation	2
PLAPS point: Thickened pleura	2

BLUE, bedside lung ultrasound in emergency; PLAPS, posterolateral alveolar and/or pleural syndrome.

Some will argue that a rapid antigen test can be used to diagnose COVID‐19 infection, as most produce a result in 15–30 min, but none of the antigenic tests so far evaluated are a robust accurate alternative to PCR for the diagnosis of COVID‐19 in symptomatic subjects or contacts of infected patients (sensitivity of 66%–74% for significant viral load, specificity between 93% and 100% depending on the tests evaluated) [3].

In conclusion, use of the COVILUS score could diagnose COVID‐19 infection with particularly good sensitivity and could facilitate more effective triage of patients presenting to emergency departments. Moreover, use of lung ultrasound could identify the signs associated with development of a severe form of COVID‐19.