# Blood test before PET or lumbar puncture

Source: https://onco.cc/ideas/da-idea-blood-first-triage/  
OnCo record `da-idea-blood-first-triage` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Use a blood test to decide who still needs a scan or spinal-fluid test, instead of sending everyone to PET.

## Summary

This is a proposed clinic pathway, not a licensed consumer diagnosis. The test has to beat sending everyone, and it has to fail safe.

## Fields

- Kind: Idea
- Last checked: 2026-09-21
- Tags: dementia-atlas
- Hypothesis: A validated plasma assay can reserve amyloid PET and CSF for people whose blood result is intermediate or whose clinical picture still needs confirmation.
- Rationale: PET and lumbar puncture are accurate but scarce. A blood-first path could shorten waits if false reassurance is controlled.
- Proposed test: Prospective memory-clinic study: plasma assay then PET or CSF reference, with pre-specified sensitivity for a negative blood test and a decision-impact endpoint (fewer unnecessary scans without missed antibody candidates).
- Maturity: early-clinical
- Actor: clinic

## Sources

- NIA: https://www.nia.nih.gov/health/alzheimers-and-dementia

## Connected records

- diagnoses: [Alzheimer’s disease](https://onco.cc/diagnoses/alzheimers-disease/), [Mild cognitive impairment](https://onco.cc/diagnoses/mild-cognitive-impairment/)
- technologies: [Blood Alzheimer biomarkers](https://onco.cc/technologies/da-tech-blood-biomarkers/)
- bottlenecks: [Late and uneven diagnosis](https://onco.cc/bottlenecks/da-bn-late-diagnosis/)
- roadmaps: [Anti-amyloid medicines](https://onco.cc/roadmaps/da-roadmap-anti-amyloid/)

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