This Lancet Neurology review considers what happens if anti-amyloid therapy is shown to work in people with no cognitive symptoms but biomarker evidence of Alzheimer's pathology. Prevention trials are running now; none has yet reported a benefit.
The authors point to three sets of problems. Ethical: what a positive or uncertain result means for a person who feels well. Accuracy: when pathology is uncommon in the people tested, a larger share of positive results will be false, and intermediate biomarker values may not reflect true disease. System: the downstream demand for confirmatory testing, imaging and monitoring that testing would create.
Blood biomarkers are increasingly easy to order. This piece is a reason to keep them for symptomatic patients being assessed in a structured pathway, and to resist testing cognitively normal people outside research until there is something proven to offer.
- Do not order Alzheimer blood biomarkers in cognitively unimpaired people outside a research setting.
- Expect more false positives when testing low-risk people, because the pathology is uncommon in them.
- Treat intermediate biomarker results as uncertain, not as early disease.
- Discuss in advance what a result would change before testing anyone with mild complaints.
Why it matters
Easy blood tests are arriving before any treatment for people without symptoms has been shown to work.
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