One-step White Blood Cell Extracellular Staining Method for Flow Cytometry.

Flow cytometry is a powerful analytical technique that is increasingly used in scientific investigations and healthcare; however, it requires time-consuming, multi-step sample procedures, which limits its use to specialized laboratories. In this study, we propose a new universal one-step method in which white blood cell staining and red blood cell lysis are carried out in a single step, using a gentle lysis solution mixed with fluorescent antibody conjugates or probes in a dry or liquid format. The blood sample may be obtained from a routine venipuncture or directly from a fingerprick, allowing for near-patient analysis. This procedure enables the analysis of common white blood cell markers as well as markers related to infections or sepsis. This simpler and faster protocol may help to democratize the use of flow cytometry in the research and medical fields. Graphic abstract: One-step White Blood Cell Extracellular Staining Method for Flow Cytometry.

Direct freezing of whole blood enables analysis of leucocyte markers by flow cytometry: a proof-of-concept study.

Aim: A new one-step flow cytometry procedure has been recently demonstrated for identifying subjects with infections, but only for fresh whole blood samples. The goal of this study was to assess its applicability on frozen samples, by proposing a new method to perform the sample freezing directly and easily. Methods: Fresh blood was tested, then frozen either directly or with dimethylsulfoxide and serum. Common markers of white blood cells as well as infection-related biomarkers were tested. Results: All percentages of leucocyte subsets and levels of infection-related biomarkers were significantly correlated between frozen and fresh samples. Conclusion: The direct freezing method enables an accurate assessment of common cellular sub-populations and of levels of important infectious biomarkers via flow cytometry.

CD169 and CD64 could help differentiate bacterial from CoVID-19 or other viral infections in the Emergency Department.

The identification of a bacterial, viral, or even noninfectious cause is essential in the management of febrile syndrome in the emergency department (ED), especially in epidemic contexts such as flu or CoVID-19. The aim was to assess discriminative performances of two biomarkers, CD64 on neutrophils (nCD64) and CD169 on monocytes (mCD169), using a new flow cytometry procedure, in patients presenting with fever to the ED during epidemics. Eighty five adult patients presenting with potential infection were included during the 2019 flu season in the ED of La Timone Hospital. They were divided into four diagnostic outcomes according to their clinical records: no-infection, bacterial infection, viral infection and co-infection. Seventy six patients with confirmed SARS-CoV-2 infection were also compared to 48 healthy volunteers. For the first cohort, 38 (45%) patients were diagnosed with bacterial infections, 11 (13%) with viral infections and 29 (34%) with co-infections. mCD169 was elevated in patients with viral infections, with a majority of Flu A virus or Respiratory Syncytial Virus, while nCD64 was elevated in subjects with bacterial infections, with a majority of Streptococcus pneumoniae and Escherichia coli. nCD64 and mCD169 showed 90% and 80% sensitivity, and 78% and 91% specificity, respectively, for identifying patients with bacterial or viral infections. When studied in a second cohort, mCD169 was elevated in 95% of patients with SARS-CoV-2 infections and remained at normal level in 100% of healthy volunteers. nCD64 and mCD169 have potential for accurately distinguishing bacterial and acute viral infections. Combined in an easy and rapid flow cytometry procedure, they constitute a potential improvement for infection management in the ED, and could even help for triage of patients during emerging epidemics.