Which of the following CSF biomarker profiles is MOST consistent with a diagnosis of Alzheimer's disease?
- A Elevated Abeta-42, decreased total tau, decreased phospho-tau
- B Normal Abeta-42 with isolated elevation of phospho-tau only
- C Decreased Abeta-42, elevated total tau, elevated phospho-tau 181 ✓
- D Elevated Abeta-42 with normal tau profile
Correct answer: C. Decreased Abeta-42, elevated total tau, elevated phospho-tau 181
Explanation
In Alzheimer's disease, CSF biomarkers show: decreased Abeta-42 (due to sequestration into amyloid plaques, less available in CSF), elevated total tau (marker of axonal/neuronal injury and neurodegeneration), and elevated phospho-tau 181 (marker of neurofibrillary tangle pathology). This AT(N) framework (Amyloid, Tau pathology, Neurodegeneration) is used for biomarker-based diagnosis. The pattern of low Abeta-42 + high tau + high p-tau is highly specific for AD pathology and is now incorporated in revised diagnostic criteria (NIA-AA 2018).
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
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Written and medically reviewed by the StethoPrep medical team.