Alzheimer's diagnostic pathways, as of Q2 2026

A reference snapshot of how Alzheimer's is diagnosed in clinical practice in mid-2026. This is a factual landscape - for analysis, see our Insight on how blood biomarkers reshape diagnosis.

Clinical assessment

The diagnostic process still begins with cognitive assessment by a primary care physician or specialist - typically using brief cognitive screens (MoCA, MMSE) and structured history. This step has not been displaced by biomarker testing.

Biomarker testing

Three biomarker modalities are in routine use, with different roles:

• Plasma biomarkers - primarily plasma p-tau217, increasingly used as a triage and rule-in / rule-out tool in symptomatic patients. Several FDA-cleared in-vitro diagnostics are now available, alongside laboratory-developed tests.
• Cerebrospinal fluid panels - Aβ42/40 ratio, p-tau, t-tau. Long-validated. Requires lumbar puncture; widely available at academic centers, less so in community practice.
• Amyloid PET imaging - clinically validated and Medicare-covered for diagnostic clarification and treatment-eligibility confirmation. Tau PET is available at fewer centers and used more selectively.

Genetic testing

APOE genotyping is now de facto standard before initiating anti-amyloid therapy, given the differential ARIA risk in homozygotes. Counselling capacity around APOE disclosure is a known constraint.

Confirmatory imaging before disease-modifying therapy

Anti-amyloid antibody initiation requires confirmation of amyloid pathology - most commonly via amyloid PET or CSF testing - and a baseline MRI to assess ARIA risk and exclude contraindications. Plasma biomarkers alone are not currently sufficient as the basis for treatment initiation.

What this snapshot does not capture

Real-world performance of plasma assays varies meaningfully across populations, and pre-analytical handling matters more than for routine chemistries. The diagnostic pathway as described above is the standard at well-equipped centers; community practice access to CSF, PET, and APOE counselling remains uneven.

The pathway above also treats the question as "Alzheimer's, yes or no." In older patients the more accurate frame is "what is the mix" - see our explainer on co-pathology in dementia and the related Signal on how co-pathology recognition is reshaping diagnosis.