Researchers at Montpellier University Hospital have discovered that an interferon-inducible receptor expressed on monocytes could be a useful biomarker for the rapid triaging of patients suspected to have severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
The team found that among patients admitted to hospital with an early-stage infection, monocytes strongly expressed the receptor, called sialoadhesin (CD169).
Edouard Tuaillon and colleagues say that testing the monocyte expression of CD169 (mCD169) could complement current viral and serology methods to improve the diagnosis of COVID-19 and help emergency departments cope with the pandemic.
“To our knowledge, the present study is the first to evaluate the value of mCD169 measurements in the rapid identification of COVID-19,” writes the team.
A pre-print version of the paper is available in the server medRxiv*, while the article undergoes peer review.
Novel Coronavirus SARS-CoV-2 Colorized scanning electron micrograph of an apoptotic cell (blue) infected with SARS-COV-2 virus particles (yellow), isolated from a patient sample. Image captured at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland. Credit: NIAID
Rapid diagnosis is a major challenge in emergency departments
Tuaillom and colleagues say that Montpellier University Hospital has been severely impacted by the COVID-19 pandemic, even though incidence in the Montpelier region was low during the peak of the epidemic (between March and April), compared to northeastern France.
According to the authors, the seroprevalence at this end of the wave was an estimated 1.9% in the Montpellier region, compared with 9.1% in the northeast of the country.
“Consequently, even at the peak incidence of SARS-CoV-2 (when the study was conducted), only some of the patients suspected of COVID-19 and admitted in dedicated care units had a confirmed diagnosis of SARS-CoV-2 infection,” writes the team.
The rapid diagnosis of COVID-19 represents a significant challenge in emergency departments, especially when the number of suspected cases is in the hundreds, but only some of those are actual infections, say the researchers.
Early detection and diagnosis are important
Early detection and diagnosis are essential for reducing the risk of severe patient outcomes and for avoiding time-consuming interventions in cases where patients are not infected but may have another serious health condition that requires the appropriate care.
Type I interferons (IFN) are important immune system components that play a major role in the immune response to viral infection.
A robust type-I IFN response in the early stage of SARS-CoV-2 infection limits viral replication, and decreases the risk of severe outcomes, explains Tuaillom and team.
Monocytes usually express low levels of CD169, but this expression significantly increases in the presence of type I IFNs. Furthermore, researchers have demonstrated overexpression of mCD169 in cases of acute viral infection.
Reorganizing service delivery in response to COVID-19
In March, Montpellier University Hospital introduced a change to the delivery of its service in response to the COVID-19 outbreak. The researchers say this improved the triaging, diagnosis, and hospitalization of suspected COVID-19 patients.
“In this prospective observational study conducted during the COVID-19 outbreak, we evaluated mCD169 expression for the identification of SARS-CoV-2 infection in patients at hospital admission,” writes the team.
Of 162 patients admitted to the respiratory emergency unit between 15th March and 5th April, the researchers selected 53 and tested their levels of mCD169 expression.
Patients with SARS-CoV-2 overexpressed mCD169
Of these 53 patients, 32 tested positive for SARS-CoV-2, and of those patients, thirty (93.7%) strongly overexpressed mCD169. By contrast, only three (14.3%) of the remaining 21 uninfected patients overexpressed mCD169.
The team reports that the mCD169 level correlated with the plasma IFNα level, but was not associated with levels of the inflammatory markers C-reactive protein or neutrophil count.
To explore whether mCD169 could complement serological testing, the researchers retrospectively assessed the patients for antibodies against SARS-CoV-2.
Among patients who had confirmed COVID-19, seven also tested positive for anti-SARS-CoV-2 immunoglobulin G (IgG) on hospital admission.
These patients had lower levels of mCD169 than patients who tested negative for these antibodies, suggesting that overexpression of mCD169 is associated with active SARS-CoV-2 infection prior to seroconversion, say Tuaillon and colleagues.
A useful biomarker for triaging patients and preserving hospital capacity
The researchers conclude that testing levels of mCD169 could be useful for rapidly triaging patients with suspected COVID-19.
“The assessment of mCD169 may complement viral and serological methods to improve the diagnosis of COVID-19,” they write.
“Alongside RT-PCR and serological testing, mCD169 may contribute to preserving the medical capacities of emergency departments by favoring the rapid orientation of patients with possible COVID-19,” concludes the team.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.