Letter to editor: Evaluation of the relationship between TREM- 1/TREM- 2 ratio and clinical course in COVID- 19 pneumonia

Dear editor, we read with great interest the well written article by Dr Kerget et al with the main objective of investigating the role of TREM-1/TREM-2 ratio on patients with COVID-19 pneumonia. The article pointed that TREM-1 and TREM-2 have important role in inflammation and TREM-1/TREM-2 ratio was higher in severe COVID-19 patients compared with moderate COVID-19 patients. We have certain comments to understand the conclusions of this article. Firstly, triggering receptor expressed on myeloid cells-1 (TREM-1) is mainly express on neutrophils and monocytes in a cell membrane-bound form. A soluble form of TREM-1(sTREM-1), which lacks the cytoplasmic tail and transmembrane part, were detected in the blood in recent studies. Since you have mentioned “serum TREM-1”, we were confused whether you detected TREM-1 or sTREM-1. Secondly, we wanted to know more about the treatment and the kidney functions of the patients. Thirdly, We are curious to see if high TREM-1/TREM-2 ratio could predict the distribution of ILD. We would be glad to hear the opinion of the author on the points, to get a more convincing conclusion.