Earlier blood biomarker results sharpened memory clinic diagnoses without more distress

Design

Prospective, single-centre randomised trial of earlier vs delayed biomarker disclosure

Population

220 new memory clinic outpatients (subjective cognitive decline, mild cognitive impairment or mild dementia), Spain

Primary outcome

Very high-confidence (90% or more) aetiological diagnosis at 3 months

Effect

50.0% vs 4.6%; symptomatic treatment started 14.3% vs 4.6% (difference 9.7 points, 95% CI 1.8 to 17.8)

In a single memory clinic in Spain, 220 new outpatients with subjective cognitive decline, mild cognitive impairment or mild dementia were randomised to hear their plasma phosphorylated tau (p-tau217) and neurofilament light chain results at 3 months or at 9 months. All received standard evaluation. The primary outcome was a very high-confidence (90% or more) aetiological diagnosis.

At 3 months, 50.0% (56 of 112) in the earlier-disclosure arm had a very high-confidence diagnosis against 4.6% (5 of 108) in the delayed arm. Earlier disclosure was associated with more symptomatic Alzheimer treatment being started (14.3% vs 4.6%; difference 9.7 points, 95% CI 1.8 to 17.8), fewer planned neuropsychological reassessments (30.4% vs 52.8%), and more planned discharge to primary care (31.3% vs 12.0%). Anxiety, depression, stress and quality of life were not worse.

The delayed arm was designed to withhold the result, so part of the difference is built in. The follow-up was nine months, from one centre, and the trial cannot show better long-term outcomes. Availability and cost of these assays in India will limit routine use for now.

• A very high-confidence diagnosis at 3 months was reached in 50.0% with early disclosure vs 4.6% with delayed disclosure.
• Earlier disclosure led to more symptomatic Alzheimer treatment (14.3% vs 4.6%).
• It also led to fewer planned repeat neuropsychological assessments (30.4% vs 52.8%).
• Anxiety, depression, stress and quality of life were not worse with earlier disclosure.
• Consider blood biomarkers as part of the diagnostic work-up where validated assays are available, alongside clinical assessment.

Why it matters

It moves blood biomarkers from a research tool to a test whose effect on routine management has been measured.

Don't overread it

A single-centre trial with a delayed-disclosure comparator shows changed confidence and management, not better patient outcomes.

The statistics, in plain English

The 50.0% vs 4.6% gap measures diagnostic confidence, not accuracy: a clinician can be confident and wrong. The gap narrowed after the delayed group received their results, which is what you would expect if the biomarker, not time, drove the change.

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