CSF p‐tau231 has been measured during the last two decades using different techniques, and it has been proven to be useful to detect AD (prodromal or dementia) (Kohnken et al, 2000; Arai et al, 2000; Blennow et al, 2001; De Leon et al, 2002; Buerger et al, 2002a; Hampel et al, 2004, 2005; Buerger et al, 2009; Glodzik‐Sobanska et al, 2009; Meredith et al, 2013; Spiegel et al, 2015; Wang et al, 2016; Öhrfelt et al, 2016; Kiđemet‐Piskač et al, 2018; Babić Leko et al, 2018; Santos et al, 2019). This evidence concerns the gene OCA2 and Alzheimer disease.