The soluble form of TREM2, sTREM2, has been found to be a useful marker of AD pathology and cognitive decline, with higher levels correlating positively with neurodegenerative markers and slower cognitive decline (Henjum et al., 2016; Heslegrave et al., 2016; Suárez-Calvet et al., 2016b; Ewers et al., 2019, 2020; Pascoal et al., 2021). This evidence concerns the gene TREM2 and Alzheimer disease.