Finger-Prick Test Shows Promise for Alzheimer Disease Biomarker Screening

A new study published in Nature Medicine details a minimally invasive method for detecting key AD biomarkers from dried blood spots.

In less than a decade, the development of blood biomarkers to identify Alzheimer disease (AD) pathology has transitioned from a promising research endeavor to a valued clinical and research tool. A key challenge limiting their widespread adoption, however, has been the logistical complexity of sample collection.

A new multicenter European study has demonstrated that key AD biomarkers can be accurately quantified from dried plasma and blood spots obtained via a simple finger prick. The findings, published online in Nature Medicine, show strong correlations with traditional venous blood tests, suggesting a scalable new approach for research and population screening.¹

P-tau217 Shows Strong but Variable Correlation

The study's primary analysis focused on phosphorylated tau at amino acid 217 (p-tau217), a leading blood biomarker for AD. The investigation included 337 participants across seven European centers, with 252 providing paired capillary dried plasma spot (DPS) and venous plasma samples for comparison. Overall, the researchers found a strong Spearman's rank correlation between p-tau217 levels from DPS and standard venous plasma (rS = 0.74, P < .001).¹

However, the strength of this correlation showed significant variability across the study sites, with values ranging from an excellent rS = 0.904 in Gothenburg to a more moderate rS = 0.429 in Malmö. The authors note that the Malmö cohort was the only one in which a different assay was used for the venous plasma comparison, likely explaining the weaker correlation.¹

Consistent with established disease patterns, DPS p-tau217 levels progressively increased with disease severity across cognitively unimpaired, mild cognitive impairment, and AD dementia groups. The method demonstrated good accuracy in predicting cerebrospinal fluid (CSF) biomarker positivity, achieving an area under the curve (AUC) of 0.864. This accuracy was, however, significantly lower than that of venous plasma p-tau217, which achieved a near-perfect AUC of 0.982 in the same participants.¹

GFAP and NfL Also Show High Concordance

The study also successfully detected two other important biomarkers: glial fibrillary acidic protein (GFAP), a marker of astrocyte reactivity, from dried blood spots (DBS), and neurofilament light (NfL), a marker of axonal damage, from dried plasma spots (DPS). The results showed a strong correlation between GFAP measured from capillary DBS and venous plasma (r = 0.773, P < .001). Similarly, a strong correlation was observed between NfL derived from capillary DPS and venous plasma (r = 0.83, P < .001).¹

Method Proves Feasible in High-Risk and Self-Collection Settings

Down Syndrome Population The method proved effective in a cohort of 31 individuals with Down syndrome, a population at high genetic risk for AD where standard venipuncture can often be complicated. In this group, capillary-derived biomarkers were significantly elevated in participants with dementia compared with asymptomatic individuals, demonstrating the test's utility in this specific high-risk population.¹

Potential for Self-Collection A pilot study involving 30 participants directly compared sample collection supervised by trained staff with unsupervised, self-collection performed an hour later. The results showed a "very high concordance" between the two collection methods, suggesting that remote, self-administered sample collection is feasible for large-scale research studies.¹

Overcoming Logistical Barriers in Research and Screening

Blood biomarkers are rapidly becoming essential tools in AD research and are increasingly adopted in clinical practice. However, current methods face significant logistical challenges, requiring venipuncture by trained personnel, timely centrifugation to separate plasma, and strict temperature-controlled storage and shipment to a specialized lab. These requirements limit widespread use, especially in primary care, remote regions, and for underrepresented populations. The dried blood spot method offers a potential solution to overcome these barriers, thereby facilitating large-scale epidemiological research and improving the diversity of clinical trial enrollment.¹

"While we're still years away from clinical use, we're opening doors to research that was previously impossible – studying diverse populations, conducting large-scale screening studies, and including communities that have been historically underrepresented in Alzheimer's research", lead author Nicholas Ashton, PhD, researcher at the University of Gothenburg and senior director at the Banner Sun Health Research Institute in Arizona, said in a press release.²

Although the study focused on AD, the authors note the reliable detection of NfL from DPS samples has broader implications. Given its established role as a diagnostic and prognostic biomarker, capillary-based NfL measurement could be transformative for other neurodegenerative conditions, including frontotemporal dementia, multiple sclerosis, and amyotrophic lateral sclerosis.¹

A Path to Clinical Use, but Key Hurdles Remain

Despite the promising results for research applications, the study authors state clearly that they do not currently recommend the use of dried blood analysis for clinical decision-making or patient management. The primary limitations include the observed differences in diagnostic accuracy compared to venous blood and a 15% to 25% rate of unsuccessful capillary sample collection. These failures were attributed to practical challenges such as insufficient capillary blood flow, coagulation, hemolysis, admixture of interstitial fluid, or technical issues during plasma separation. Furthermore, the technique was unable to reliably quantify the Aβ42 biomarker.¹

“Further methodological refinement and validation will be essential before clinical translation can be considered,” investigators concluded.¹

References:

1. Huber H, Montoliu-Gaya L, Brum WS, et al. A minimally invasive dried blood spot biomarker test for the detection of Alzheimer’s disease pathology. Nat Med. Published online January 5, 2026. doi:10.1038/s41591-025-04080-0
2. Home blood test opens up for new Alzheimer's research. News release. University of Gothenburg. January 5, 2025. Accessed January 6, 2025. https://www.gu.se/en/news/home-blood-test-opens-up-for-new-alzheimers-research