Early Alzheimer’s Biomarker Test Results Boost Diagnostic Certainty, Guide Clinical Care
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A randomized trial shows that earlier access to Alzheimer’s blood biomarker results increases diagnostic certainty and alters clinical management.
Earlier disclosure of Alzheimer’s disease (AD) blood test results increased physicians’ diagnostic certainty and changed clinical management in patients evaluated for cognitive symptoms without raising patient anxiety or depression.
Results of the first randomized trial to assess the clinical impact of these tests rather than diagnostic accuracy alone showed that disclosing plasma phosphorylated tau at threonine 217 (p-tau217) and neurofilament light chain (NfL) results at 3 months vs 9 months raised the proportion of patients with a very high-confidence (≥ 90%) etiologic diagnosis from 4.6% to 50%.
Furthermore, physicians with early access to the results also initiated pharmacologic treatment more frequently (14% vs 5%) and planned more discharges to primary care (31% vs 12%).
“The main take-home message is that the value of blood-based biomarkers goes beyond diagnostic accuracy,” study investigator Albert Puig-Pijoan, MD, PhD, Barcelona Brain Health Center, Hospital del Mar, Barcelona, Spain, told Medscape Medical News. “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,” Puig-Pijoan added.
The study was published online in JAMA Neurology.
From Diagnostic Accuracy to Clinical Utility
p-tau217 is highly accurate for identifying AD pathology, while NfL, although not specific for AD, may provide complementary information on neurodegeneration.
In 2025, clinical practice guidelines supported the use of blood-based biomarkers in specialized care. However, evidence that these tests improve diagnostic certainty, management decisions, or other clinically relevant outcomes has remained limited.
The goal of the PLASMAR trial was to address that gap. It included 220 patients undergoing evaluation for subjective cognitive decline, mild cognitive impairment (MCI), or mild dementia at a single memory clinic in Spain. Participants were randomly assigned to disclosure of plasma p-tau217 and NfL results at 3 months (n = 112) or 9 months (n = 108).
Puig-Pijoan described the finding as particularly significant for clinical practice, noting that earlier access to biomarker results could help clinicians identify patients who may benefit from timely treatment while sparing others unnecessary specialist follow-up. This approach could also provide patients with greater diagnostic certainty sooner and help memory clinics use their resources more efficiently.
