This clinicopathologic CSF biomarker study in patients with AD and FTLD, which included Aβ42/Aβ40, P-tau, and P-tau/Aβ42 measured with fully automated Elecsys assays and NFL measured with an ultrasensitive Simoa assay, found that specific biomarkers were strongly correlated with AD, including when AD was present as copathology in patients with another primary pathology. The gene discussed is MAPT; the disease is Alzheimer disease.