C9ORF72 EXPANSION DOES NOT HAVE EFFECTS ON CSF TDP-43 LEVELS IN FTLD PATIENTS

when making a diagnosis of AD. In this study, we evaluated how clinicians consider CSF biomarkers in the diagnosis and treatment of patients with possible dementia. Methods: Participants (N 1⁄4 193) were physicians and other medical professionals who evaluate older adults for neurodegenerative dementing diseases. In this within-subjects clinical vignette study, participants were randomized to view normal, borderline, AD-consistent, or no CSF information in two vignettes portraying patients with borderline and mild AD symptoms. In addition, clinicians reported on the use and perceived utility of CSF laboratory results in clinical practice. Results: Clinicians reported current infrequent use and limited perceived utility of CSF biomarkers in clinical practice, yet CSF biomarkers affected clinical decisionmaking. ViewingAD-consistent CSF valuesmade clinicians 6-12 times more likely to make an AD-related diagnosis (p< .01), increased diagnostic confidence (p< .05), and led clinicians to initiate treatment more often than clinicians who had no CSF information (p 1⁄4 .004). Conclusions: CSF biomarkers can influence clinical decisions and have different effects depending on the extent to which biomarkers reflect AD pathology, consistency between clinical-pathological information, and ambiguity or clarity of protein values. Clinicians should consider potential biases when integrating CSF biomarker values in clinical decisions.