Identification of patients with an activation of the immune system during inflammation in lung disease is essential. Clinicians need to distinguish between inflammations caused by infections and other mechanism. To support a fast initial indication, the new diagnostic RE-LYMP and AS-LYMP parameters for the quantitatively assessment of activated lymphocytes are available on haematological analysers.

The aim of the study was to evaluate the reactive lymphocytes (RE-LYMP) parameter and antibody-synthesizing lymphocytes (AS-LYMP) parameter in COVID-19 and sarcoidosis patients using haematology analyser. RE-LYMP describe reactive lymphocytes and reflects all lymphocytes that have a higher fluorescence signal than the normal lymphocyte population. The AS-LYMP parameter describe the activated B lymphocytes that synthesise antibodies. We correlated these parameters with plasmablasts assessed by flow cytometry.

We found that COVID-19 and SA patients had significantly higher RE-LYMP parameter than healthy control group (HC)  (p< 0.05). Patients with COVID-19 had higher RE-LYMP parameter than SA patients (p> 0.05). Interestingly, SA patients had significantly higher AS-LYMP parameter than COVID-19 patients and HC. In SA patients the AS-LYMP parameter correlated with the percentage of plasmablasts in peripheral blood.

In summary, the analysis of RE-LYMP and AS-LYMP parameter together with flow cytometry can be helpful in explaining the pathogenesis of COVID-19 and sarcoidosis patients.