There is strong evidence that plasma p-tau is a reliable biomarker for AD, with demonstrated utility in multiple clinical contexts; these include AD time course [45], definitive diagnosis and differential diagnosis versus other causes of cognitive impairment [15,16▪▪,17▪▪,21,22▪▪,46▪], disease prognosis in primary care [15,17▪▪], and in participant selection and efficacy monitoring in therapeutic trials [18▪▪,20▪▪]. The gene discussed is MAPT; the disease is Alzheimer disease.