Blood Biomarker Disclosure Speeds Confident Diagnosis of Cognitive Decline

Earlier disclosure of plasma phosphorylated tau at threonine 217 (p-tau217) and neurofilament light chain (NfL) results increased etiologic diagnostic certainty among patients evaluated for cognitive symptoms in a memory clinic, according to a randomized clinical trial published in JAMA Neurology.

The single-center PLASMAR trial, conducted at Hospital del Mar in Barcelona, Spain, randomized 220 consecutive new outpatients with subjective cognitive decline, mild cognitive impairment (MCI), or mild dementia and no prior etiologic diagnosis (median age, 73 years; 55.9% women). Results were disclosed to the treating neurologist and participant at 3 months (earlier disclosure) or 9 months (delayed disclosure), alongside standard clinical evaluation.

At 3 months, a very high-confidence etiologic diagnosis (≥90%) was reached in 50.0% of the earlier-disclosure arm vs 4.6% of the delayed-disclosure arm (P < .001). Diagnostic certainty converged after disclosure in both arms, except among participants with MCI, in whom higher certainty persisted with earlier disclosure.

Earlier disclosure was also associated with more frequent initiation of symptomatic Alzheimer disease treatment (14.3% vs 4.6%; difference, 9.7; 95% CI, 1.8-17.8), fewer planned follow-up neuropsychological reassessments (30.4% vs 52.8%), and more planned discharge to primary care (31.3% vs 12.0%). It was not associated with worse emotional outcomes; perceived stress increased in the delayed-disclosure arm before disclosure.

The investigators noted that the trial was single center, that planned investigations and follow-up were recorded as clinician-intended management rather than mandated actions, and that it was not designed to determine whether earlier treatment improved cognition, function, or disease course. Follow-up was limited to approximately 9 months, and no adjustment was made for multiple comparisons.

Source: Estragués-Gázquez I, Contador J, Martínez LD, et al. Earlier disclosure of blood-based biomarkers, diagnostic certainty, and clinical management: a randomized clinical trial. JAMA Neurol. Published online October 5, 2026. doi:10.1001/jamaneurol.2026.3497