The strengths of our study include (i) the validation and application of an easy‐to‐use ELISA kit to measure CSF levels of the microglial marker TMEM119, (ii) the measurement of CSF TMEM119 levels in patients with a variety of neurodegenerative diseases, and (iii) the comparison of CSF levels of TMEM119 with other AD biomarkers. Here, TMEM119 is linked to Alzheimer disease.