TREM2 and Alzheimer disease: Complex interactions continue to be explored, including how TREM2 and sTREM2 correlate with tau and phosphorylated tau (p-tau) levels in both CSF samples and post-mortem AD brain tissues, unaffected by the presence of Aβ (Cruchaga et al., 2013; Suárez-Calvet et al., 2019; Vogels et al., 2019).