Healthier World with Quest Diagnostics
Episode 32 – Instant Insights: Blood-Based Biomarkers for Alzheimer’s Disease
Date: March 2, 2026
Host: Dr. Mason Latsko (Quest Diagnostics)
Duration: 8 minutes

Episode Overview

This Instant Insights episode, hosted by Dr. Mason Latsko, delves into the emerging role of blood-based biomarkers in the diagnosis and management of Alzheimer’s disease. The episode covers the limitations of traditional diagnostic methods, recent advances in blood-based testing, the specific biomarkers involved, and the practical impact on clinical decision-making. Dr. Latsko emphasizes how these innovations may help clinicians achieve earlier and more precise diagnoses, while also differentiating Alzheimer’s from other potential causes of cognitive decline.

Key Discussion Points & Insights

The Challenge of Diagnosing Alzheimer’s Disease

• Prevalence:
  • Over 55 million people globally, with 7 million older adults in the US living with Alzheimer’s.
  • One of the most common and costly neurodegenerative diseases.
• Diagnostic Delay:
  • Alzheimer’s often diagnosed after symptom onset due to reliance on expensive imaging or invasive tests.
  • “Despite how prevalent Alzheimer's disease is, it's often diagnosed late, after symptoms have already begun to interfere with daily life.” (Dr. Latsko, 01:02)

Shift to Blood-Based Biomarkers

• Historical Barriers:
  • Diagnosis previously relied on brain imaging (PET) or lumbar puncture, not practical for broad early screening.
• Evolving Paradigm:
  • New blood-based biomarkers now guideline-supported, offering earlier, accessible, less invasive assessment.
  • “We're entering into a new era of dementia care, one where blood-based biomarkers are guideline-supported to help clinicians gain biological insights into what's happening in the brain earlier and in a way that's potentially more accessible than ever before.” (Dr. Latsko, 01:25)

Understanding Alzheimer’s Pathology

• Key Features:
  • Alzheimer’s is characterized by amyloid beta plaques (outside neurons) and tau tangles (inside neurons).
  • Amyloid plaques disrupt neuron communication; tau tangles impair internal cell transport, leading to cell death and cognitive decline.
• Clinical Overlap:
  • Many dementias (vascular, Lewy body, frontotemporal, some reversible causes) share symptoms; biomarkers help clarify etiology.

The Core Biomarkers Discussed

1. Amyloid Beta 42/40 Ratio

• Plaque Formation Indicator:
  • Amyloid beta 42 builds up in Alzheimer’s, reducing its level in blood relative to beta 40, yielding a low 42/40 ratio.
  • “A low plasma Abeta 42/40 ratio has been shown to be correlated with amyloid PET positivity and reflects the process of amyloid plaque deposition.” (Dr. Latsko, 03:14)
• Clinical Relevance:
  • Offers a non-imaging, non-invasive surrogate of amyloid pathology.
  • Particularly useful for patients with mild cognitive impairment.

2. Phosphorylated Tau (P-Tau 217)

• Specificity for Alzheimer’s:
  • Elevated plasma P-Tau 217 correlates strongly with tau and amyloid PET positivity, indicating Alzheimer’s pathology.
  • “Tau pathology is closely linked to neuronal injury and disease progression in Alzheimer's disease.” (Dr. Latsko, 04:14)
• Added Value:
  • Provides an additional layer of specificity beyond amyloid biomarkers.

3. Combined Testing Approach

• Diagnostic Confidence:
  • Simultaneous testing improves accuracy in detecting both amyloid and tau pathology.
  • “Combining tests such as the Amyloid Beta 42/40 and P Tau 217 can improve diagnostic confidence in symptomatic patients.” (Dr. Latsko, 05:06)

The AD Detect Panel (Quest Diagnostics)

• Panel Features:
  • Measures both Abeta 42/40 ratio and P-Tau 217.
  • Uses a model to generate a likelihood score of PET positivity.
  • “...over 90% sensitivity and specificity and a 15% indeterminate rate, which is within acceptable parameters...” (Dr. Latsko, 05:38)
• Interpretation:
  • High likelihood scores support consideration of Alzheimer's disease and guide next steps; indeterminate results require clinical context.

Differentiating Alzheimer’s from Other Causes

• Non-Alzheimer’s Causes:
  • Not all cognitive decline is due to Alzheimer's.
  • Modifiable secondary causes include diabetes, thyroid disease, kidney disease, fatty liver, sleep disturbances, nutritional deficiencies.
• Role of Biomarkers:
  • Help distinguish neurodegenerative from reversible/metabolic causes.
  • “Blood-based biomarkers serve to indicate whether or not these comorbidities are leading to cognitive impairment or whether symptoms are arising due to amyloid and plaque pathology.” (Dr. Latsko, 06:32)

Practical Applications in Clinical Practice

• Advantages:
  • Supports differentiation between Alzheimer’s and other dementias.
  • Enables earlier intervention and prognosis discussions.
  • Guides eligibility for disease modifying therapies or trials.
  • Intended for adults over 55 with cognitive symptoms suggestive of mild cognitive impairment.
• Role of Clinical Judgement:
  • “Blood-based biomarkers are not replacing clinical judgment, but they are enhancing it.” (Dr. Latsko, 07:10)

Notable Quotes & Memorable Moments

• On Changing Diagnostic Paradigms:
  • “We're entering into a new era of dementia care...” (01:25)
• On the Power of Combining Markers:
  • “Combining tests such as the Amyloid Beta 42/40 and P Tau 217 can improve diagnostic confidence...” (05:06)
• On Clinical Utility:
  • “These tests can help support a confident diagnosis decision and help guide next steps.” (07:21)
• On the Excitement of the Field:
  • “This is a very exciting time for Alzheimer's disease identification.” (07:01)

Key Segment Timestamps

• Introduction and Scope of Alzheimer’s Disease: 00:00 – 01:20
• Transition to Blood-Based Biomarkers: 01:20 – 02:50
• Description of Pathology and Biomarkers: 02:50 – 05:00
• Details on AD Detect Panel and Accuracy: 05:00 – 06:00
• Non-Alzheimer’s and Modifiable Causes: 06:00 – 06:45
• Clinical Implications and Conclusion: 06:45 – 07:50

Summary

Dr. Mason Latsko uses this concise, insightful episode to showcase how blood-based biomarkers (Amyloid Beta 42/40 and P-Tau 217) are transforming Alzheimer’s disease evaluation. The AD Detect panel’s high sensitivity and specificity empower clinicians to identify pathology earlier and more practically than ever before, aiding differentiation from other cognitive disorders and guiding appropriate patient management. As Dr. Latsko concludes, these advances are not a replacement for clinical judgment but a significant enhancement in moving Alzheimer’s diagnosis—and care—into a more hopeful, proactive era.