Early disclosure of Alzheimer’s disease blood test results significantly raises physician diagnostic certainty and changes clinical management without increasing patient anxiety or depression, according to findings published in JAMA Neurology on October 5. Medscape reported that the first randomized trial assessing the clinical impact of plasma phosphorylated tau at threonine 217 (p-tau217) and neurofilament light chain (NfL) results at 3 months versus 9 months demonstrated a rise in high-confidence diagnoses from 4.6% to 50% for patients evaluated with cognitive symptoms.
PLASMAR Trial Evaluates 220 Patients in Spain
To address the limited clinical evidence surrounding blood biomarkers in specialized care, the PLASMAR trial evaluated 220 patients undergoing assessment for subjective cognitive decline, mild cognitive impairment (MCI), or mild dementia at a single memory clinic in Spain. Participants had a median age of 73 years, and 56% were women. At the baseline evaluation, 46% presented with subjective cognitive decline, 31% showed mild cognitive impairment, and 24% exhibited mild dementia.
All participants completed standard diagnostic workups consisting of neurologic and neuropsychological assessments, structural imaging, and laboratory tests. Clinicians ordered additional evaluations, such as cerebrospinal fluid biomarkers or amyloid PET scans, when clinically indicated. Investigators then randomly assigned participants to receive plasma p-tau217 and NfL biomarker disclosure at either 3 months (112 patients) or 9 months (108 patients).
Diagnostic Certainty and Clinical Management Shifts at Three Months
By the 3-month mark, 50.0% of individuals in the early-disclosure group reached a very high-confidence etiologic diagnosis of at least 90% certainty, compared with just 4.6% of patients in the delayed-disclosure group. Once the delayed group eventually received their biomarker results, certainty levels converged; at 9 months, 58.0% of the early group and 52.8% of the delayed group held very high diagnostic certainty. Higher certainty persisted past 9 months specifically among patients with MCI, a trend investigators attribute to the greater baseline prognostic uncertainty in that syndrome where early biological data anchors clinical judgment.
This clarity directly altered patient care. At 3 months, physicians reclassified etiologic diagnoses in 23.3% of the early-disclosure group versus 7.0% of the delayed group. For patients initially suspected of having Alzheimer’s disease, diagnoses shifted in 30.6% of early-disclosure cases compared to 6.5% of delayed cases. Physicians with early biomarker access initiated symptomatic treatment more frequently at 14.3% versus 4.6%, and planned fewer follow-up neuropsychological reassessments at 30.4% versus 52.8%. Physicians also planned more discharges to primary care at 31% versus 12.0%.
Albert Puig-Pijoan, MD, PhD, a study investigator at the Barcelona Brain Health Center at Hospital del Mar in Barcelona, Spain, explained the results to Medscape Medical News:
The main take-home message is that the value of blood-based biomarkers goes beyond diagnostic accuracy,
Albert Puig-Pijoan, MD, PhD, Barcelona Brain Health Center, Hospital del Mar, Barcelona, Spain
Puig-Pijoan added:
Having this information earlier in the diagnostic pathway can lead to earlier diagnostic certainty and earlier appropriate treatment, while also helping avoid unnecessary reassessments or prolonged specialist follow-up in some patients, without increasing psychological distress,
Albert Puig-Pijoan, MD, PhD
Addressing the psychological impact on patients, Puig-Pijoan noted:
Biomarker disclosure was not associated with increased anxiety or depressive symptoms or with worse quality of life. Perceived stress even showed a more favorable trajectory with earlier disclosure. Still, disclosure should be individualized, taking into account each patient’s clinical context, emotional state, and preferences,
Albert Puig-Pijoan, MD, PhD
While p-tau217 reliably identifies Alzheimer’s pathology and NfL provides complementary neurodegeneration data, clinical guidelines in 2025 supported biomarker use primarily in specialized care while real-world management impact remained understudied. Independent experts welcomed the randomized methodology of the trial.
Sheena Aurora, MD, vice president of medical affairs at the Alzheimer’s Association, who was not involved in the research, noted:
Earlier research showed that blood-based biomarkers can accurately detect Alzheimer’s pathology. This study takes an important step forward from asking, ‘How accurate are Alzheimer’s blood tests?’ to ‘Do they actually help patients and clinicians?’
Sheena Aurora, MD, Alzheimer’s Association
Aurora further observed:
This suggests Alzheimer’s blood biomarker tests can support earlier, more targeted clinical decision-making,
Sheena Aurora, MD
At the same time, Aurora cautioned that blood tests remain not stand-alone diagnostics
and require deployment within comprehensive evaluations alongside confirmatory testing for intermediate results. The study received no commercial funding, and larger multicenter trials with extended follow-up remain necessary to establish broader patient outcome data.
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