Cell-free sensitivity.

Among 43 CSF samples from 22 patients with previous cytology-proven leptomeningeal disease, cytology was again positive in only 31 samples (72%) while cell-free tumor DNA was positive in 40 (93%), the caveat being that cell-free DNA can produce false positives when parenchymal brain tumors abut the CSF. | White, JAMA Netw Open 2021