INDIVIDUAL TEST 997

Beta Amyloid Ratio 42/40

Indication

Suspicion of Alzheimer's disease and in memory investigation

Sample material

CSF

• Minim. volume: 0,5 mL

Transport

• Within Sweden: frozen
• International: frozen

Method

Chemiluminescence enzyme immunoassay (CELEIA)

Reference interval

>0.72 (≥ 50 years)

Result

Results are reported as a ratio.

Interpretation

When beta-Amyloid 42 aggregates in plaques, the ratio of beta-Amyloid 42/40 in CSF decreases. Decreased ratio can be found in early stages of Alzheimer's disease and can also be seen without evident cognitive impairment.

References

• Hansson O et al. Alzheimers Res Ther. 2019. Advantages and disadvantages of the use of the CSF Amyloid β (Aβ) 42/40 ratio in the diagnosis of Alzheimer's Disease. PMID: 31010420
• Dumurgier J et al. Alzheimers Res Ther. 2015. Cerebrospinal fluid amyloid-β 42/40 ratio in clinical setting of memory centers: a multicentric study. PMID: 26034513
• Woyk K et al. J Alzheimers Dis Rep. 2025. The relationship of 18F-FDG-PET to other common biomarkers of dementia in a clinical cohort with memory deficits. PMID: 40290782
• Amft M et al. Alzheimers Res Ther. 2022. The cerebrospinal fluid biomarker ratio Aβ42/40 identifies amyloid positron emission tomography positivity better than Aβ42 alone in a heterogeneous memory clinic cohort. PMID: 35473631
• Martino-Adami PV et al. Lancet Reg Health Eur. 2024. Prognostic value of Alzheimer's disease plasma biomarkers in the oldest-old: a prospective primary care-based study. PMID: 39253733
• Jack CR Jr et al. Alzheimers Dement. 2024. Revised criteria for diagnosis and staging of Alzheimer's disease: Alzheimer's Association Workgroup. PMID: 38934362

Last updated: 2025-12-05