The medical world’s push for precision medicine has created a paradox where doctors must navigate between testing too many biomarkers and missing critical ones that could save lives.
Story Overview
- New 2025 Alzheimer’s guidelines specify exactly which blood biomarkers to test, ending years of uncertainty
- Cancer biomarker testing rates remain stuck at only 35-39% despite expanded insurance coverage
- Over-testing leads to false positives and unnecessary anxiety, while under-testing misses targeted therapy opportunities
- State legislatures are mandating biomarker testing coverage to close access gaps
- Clinical utility, not comprehensive panels, should determine which biomarkers get tested
The Goldilocks Problem of Biomarker Testing
Doctors face a medical version of the Goldilocks dilemma: too few biomarker tests leave patients without optimal treatments, while too many create false alarms and skyrocketing costs. The July 2025 release of the Alzheimer’s Association’s first clinical practice guideline for blood-based biomarkers attempts to solve this puzzle by specifying exactly which markers clinicians should test for cognitive impairment patients in specialty care settings.
This precision approach contrasts sharply with the shotgun strategy some providers have adopted. The new guidelines recommend plasma p-tau and amyloid-beta ratios specifically, rejecting the “test everything” mentality that has plagued the field. Expert panels used rigorous GRADE methodology to ensure each recommended biomarker meets strict accuracy thresholds before making it into clinical practice.
Cancer Testing Falls Short Despite Clear Guidelines
Oncology reveals the stark gap between what guidelines recommend and what actually happens in practice. Despite clear directives to test specific biomarkers like RAS, BRAF, MMR, MSI, and HER2 in metastatic colorectal cancer, actual testing rates hover between 35-39%. This means roughly six out of ten patients with advanced cancer never receive the biomarker testing that could identify life-saving targeted therapies.
Comprehensive genomic profiling has emerged as the preferred approach in oncology, allowing doctors to test multiple biomarkers simultaneously rather than piecemeal. Studies demonstrate this strategy improves outcomes without increasing overall costs, yet adoption remains frustratingly inconsistent. Provider awareness, access barriers, and insurance coverage gaps continue to prevent optimal implementation despite the clear clinical benefits.
Insurance Coverage Drives Testing Reality
The biomarker testing landscape shifted dramatically in 2025 as multiple states enacted legislation mandating insurance coverage for clinically indicated tests. New Jersey’s Assembly led the charge, recognizing that coverage determines which patients receive potentially life-changing diagnostics. The Large Urology Group Practice Association pushed for comprehensive coverage standardization across all insurers and Medicaid plans.
These policy changes address a fundamental truth about biomarker testing: clinical guidelines mean little if patients cannot afford the tests. Previous coverage inconsistencies created a two-tiered system where wealthy patients accessed cutting-edge diagnostics while others relied on outdated approaches. The 2025 legislative push aims to eliminate these disparities by making coverage decisions based on clinical evidence rather than cost considerations.
Evidence-Based Limits Prevent Testing Overreach
The most sophisticated answer to “how many biomarkers” lies in clinical utility rather than technological capability. Leading medical organizations consistently emphasize testing only those biomarkers with proven benefit for specific disease contexts and patient populations. The Alzheimer’s Association guideline panel deliberately avoided endorsing specific commercial tests, citing insufficient evidence for head-to-head comparisons.
This restraint reflects hard-learned lessons about biomarker testing’s potential downsides. Over-testing generates false positives that trigger unnecessary anxiety, additional procedures, and cascading healthcare costs without improving patient outcomes. The optimal number of biomarkers varies by disease, patient characteristics, and available targeted therapies rather than following a one-size-fits-all formula that prioritizes comprehensive testing over clinical relevance.
Sources:
AAIC Clinical Practice Guideline Blood-Based Biomarkers
LUGPA Expanding Coverage of Biomarker Testing in 2025
Pfizer ASCO QI Technology Solutions Biomarker Testing
ASCO Post Biomarker Testing in Advanced Cancer
American Cancer Society Precision Medicine Fact Sheet
Alzheimer’s & Dementia Journal Clinical Practice Guideline
