Validation of monocyte CD169 expression as a valuable rapid diagnostic marker of SARS-CoV-2 and other acute viral infections.

Objectives: Acute infectious diseases are some of the most common reasons for receiving medical care, and analysis of the host immune response is an attractive approach for their diagnosis. The present study aimed to evaluate the potential usefulness of CD169 expression on peripheral monocytes (mCD169) as a marker of viral-associated host immune response.

Methods: In a large mono-institutional cohort of 4,025 patients evaluated for SARS-CoV-2 (CoV2) and other viral infections, mCD169 analysis was performed by rapid flow cytometry assay.

Results: Increased mCD169 values (median, 17.50; IQR, 8.40-25.72) were found in 1,631 patients with CoV2+ acute infection compared to 2,394 in CoV2- patients (median, 2.35; IQR, 2.0-3.25) (odds ratio [OR], 21.84; 95% CI ,17.53-27.21; P < .001). Among CoV2- patients, 1,484 (62.0%) were assessed for other viral infections, and viral etiology was laboratory confirmed in 428 patients (CoV2- Vir+), with RNA viruses most frequently detected (94.6%). Higher levels of mCD169 were also confirmed in CoV2- Vir+ compared to CoV2- Vir- patients (OR, 10.05; 95% CI, 7.35-13.74; P < .001).

Conclusions: mCD169 analysis by rapid flow cytometry assay may be a sensitive broad marker useful for the rapid triage of patients with suspected acute viral infections and could potentially be directly applied to eventual new emergent viral outbreaks.