Beyond CSF: Quanterix’s Simoa Platform Brings Blood-Based Biomarkers to the Forefront

Mark Roskey, PhD

Diagnosing Alzheimer disease (AD) has long been challenging due to symptom overlap with other neurodegenerative disorders and the reliance on invasive or expensive testing methods like PET scans and cerebrospinal fluid (CSF) analysis. These limitations often delay early detection, making it harder for clinicians to intervene before significant cognitive decline occurs. As new therapies emerge, the need for accurate, accessible diagnostic tools has become more urgent than ever.

At the 2025 AD/PD International Conference on Alzheimer’s and Parkinson’s Diseases, held April 1-5 in Vienna, Austria, Quanterix, a digital biomarker technology company, presented over 80 posters, presentations, and sessions that featured its Simoa technology. Over the years, Simoa technology has delivered the gold standard for earlier biomarker detection in blood, serum, or plasma, with the ability to quantify proteins that are far lower than the level of quantification.

During the meeting, NeurologyLive® sat down with Mark Roskey, PhD, chief scientific officer at Quanterix, to discuss the company’s technology, its function, and role in the diagnosis of AD. In the discussion, Roskey highlighted the critical role of phosphorylated tau (p-tau)217 as the leading biomarker for early detection and disease monitoring, as well as advancements in multiplex biomarker panels that combine markers like glial fibrillary acidic protein (GFAP), neurofilament light (NfL), and amyloid proteins for more comprehensive analysis. In addition, he spoke on the recently introduced Lucent AD Complete, a newly launched diagnostic tool designed to improve clarity in AD testing by reducing ambiguous results.

NeurologyLive: How does the Simoa technology function?

Mark Roskey, PhD: We have about 80 presentations here at AD/PD. Our technology relies on standard immunoassay methods as a tool for biomarker analysis. As you know, the use of biomarkers in Alzheimer's, Parkinson's, and neurodegeneration is really coming to the forefront. This advancement is enabling the development of new therapeutics that will significantly impact the market.

Our unique Simoa technology is an immunoassay, but we apply a unique approach—we perform the immunoassay on a bead, place that bead in a femtoliter well, and count them. Essentially, this transforms a standard analog immunoassay into a digital one, improving sensitivity by roughly 1,000-fold. That means we can now measure neurodegeneration biomarkers in blood that previously could only be detected in cerebrospinal fluid (CSF). That's the key advantage of our technology.

What specific biomarkers does this technology test for? Are any more valuable than others?

It's been an interesting evolution. Initially, we could only test these biomarkers in CSF, but now we can detect them in blood. The first one we developed was tau protein, which is crucial for measuring tau tangles and accumulations relevant to Alzheimer's disease. Over the past decade, we've expanded to include other biomarkers. Another major one is neurofilament light (NfL), a general marker for neurodegeneration—not just Alzheimer's, but all types.

However, the most impactful development has been in measuring tau subspecies, which closely track with Alzheimer's disease. It started with phosphorylated tau 181 (p-tau 181), which made a big impact in the field. But now, p-tau 217 has emerged as the most critical biomarker for Alzheimer's, as it strongly correlates with PET imaging for the disease. We developed one of the first and most sensitive tests for this marker.

Beyond that, we're also working on biomarkers related to neuroinflammation, like GFAP, and combining these into multiplex panels to provide deeper insights into disease onset and progression. That's a major focus for us at Quanterix.

Are there challenges in learning to use Simoa technology?

Not really. One of the benefits of Simoa technology is that it's still an immunoassay, so it's based on well-established techniques. Of course, since it’s ultra-sensitive, users need to take a bit more care when running it.

That said, we’ve designed our instruments to be easy to use. We offer an automated "bead-to-read" platform—just input a sample, and you get results. For more experimental work, a standard lab technician can set up and run the assays without any issue.

We've also developed highly validated assay kits. The industry taught us that for clinical trials, we needed kits that were not only research-grade but also simple to use, with clear instructions and highly reproducible results. Since neurology studies often span years, ensuring long-term consistency is crucial.

Today, there are over 1,000 platforms in the field, 500 biomarkers analyzed using Simoa, and more than 3,000 high-level publications featuring the technology. That speaks to its usability.

Among the many Quanterix presentations at AD/PD, what stands out?

A few things align with what I mentioned earlier, especially regarding p-tau 217 for early detection. But now, with new therapeutics entering the market, there's a need to track patient responses to treatment.

At this meeting, we're seeing new research on tau isoforms like p-tau 205 and p-tau 212, which could help monitor disease progression and treatment effects. We're also working on new biomarker assays for synaptic proteins—this is groundbreaking, and we’re presenting some of that work here.

For clinicians, the next step is bringing these tests to patient care. To that end, Quanterix has formed Lucent, a division focused on diagnostic applications. At this meeting, we’re launching Lucent AD Complete, a test measuring p-tau 217 alongside Aβ40, Aβ42, GFAP, and NfL. This multi-marker approach reduces the "intermediate zone"—an issue in existing AD tests where results aren’t clear-cut. Previously, about 30% of cases fell into this zone, but our assay has brought that down to around 10%, providing clearer results for more patients.

As the field continues to evolve, what are your next steps in advancing this technology?

We’re very excited about where this is going. In addition to identifying newer biomarkers that offer deeper biological insights, we’re also making our technology even more sensitive.

Right now, Simoa is already significantly more sensitive than traditional immunoassays. But later this year, we’re launching a next-generation platform that will be 100 times more sensitive than our current system. This will allow us to detect even more subtle biological changes, providing more precise clinical insights.

Beyond sensitivity, we’re also expanding our biomarker portfolio to differentiate between different neurodegenerative diseases—Alzheimer’s, frontotemporal dementia, Parkinson’s, and others.

Finally, we’re focused on integrating our data with large-scale clinical studies, including collaborations with ADDF and AD/PD researchers. By linking biomarker data with real-world clinical outcomes, we can help drive the field forward.

Transcript was edited for clarity. Click here for more AD/PD 2025 coverage