Role of triggering receptor expressed on myeloid cells-1 (TREM-1) in COVID-19 and other viral pneumonias: a systematic review and meta-analysis of clinical studies

BACKGROUND: Triggering receptor expressed on myeloid cells-1 (TREM-1) has emerged as an important inflammatory marker of immune response associated with severity and mortality outcomes in infection diseases, including viral pneumonias. AIM: (1) To evaluate the expression of TREM-1 in patients with COVID-19 and other viral pneumonias compared to healthy individuals; and (2) to analyze the levels of these biomarkers according to disease severity. MATERIALS AND METHODS: This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Searches were performed in PubMed, Scopus, Embase, and Google Scholar. Studies were considered eligible if they were observational studies that provided data on the levels of TREM-1 in humans with viral pneumonia compared to healthy controls. The results of the meta-analysis were expressed as standardized mean difference (SMD) and an effect size of 0.8 was considered a large effect. A subgroup analysis was performed according to the disease severity. RESULTS: Seven studies were included in this systematic review. Four studies included patients with COVID-19 and three analyzed patients with different viruses. The meta-analysis was performed only with patients with COVID-19, which showed increased levels of soluble form of TREM-1 (sTREM-1) among patients with COVID-19 compared to healthy controls (SMD 1.53; 95% CI 0.53–2.52; p < 0.01). No differences were found between patients with mild-to-moderate COVID-19 and healthy controls, but higher levels of sTREM-1 were shown among patients with severe COVID-19 (SMD 1.83; 95% CI 0.77–2.88; p < 0.01). All three studies including patients with other viral pneumonias showed that TREM-1 levels were significantly elevated in infected patients compared with controls. CONCLUSION: These findings may provide evidence on the pro-inflammatory role of TREM-1 in these infections, contributing to the inflammatory profile and disease progression. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10787-022-00972-6.