The median effect size (raw mean difference) of tau level in Alzheimer's disease studies was 429 pg/mL (range: 32 to 910 pg/mL) whereas in dementia-due-to-other-causes studies it was 69 pg/mL (range: −53 to 518 pg/mL). This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.